quantrs2_sim/

jit_compilation.rs

//! Just-in-time compilation for frequently used gate sequences.
//!
//! This module provides advanced JIT compilation capabilities for quantum circuit
//! simulation, enabling compilation of frequently used gate sequences into optimized
//! machine code for dramatic performance improvements.

use scirs2_core::ndarray::{Array1, Array2};
use scirs2_core::parallel_ops::{IndexedParallelIterator, ParallelIterator};
use scirs2_core::Complex64;
use std::collections::{HashMap, VecDeque};
use std::fmt;
use std::hash::{Hash, Hasher};
use std::sync::{Arc, Mutex, RwLock};
use std::time::{Duration, Instant};

use crate::circuit_interfaces::{InterfaceGate, InterfaceGateType};
use crate::error::{Result, SimulatorError};

/// JIT compilation configuration
#[derive(Debug, Clone)]
pub struct JITConfig {
    /// Minimum frequency threshold for compilation
    pub compilation_threshold: usize,
    /// Maximum number of gates in a compilable sequence
    pub max_sequence_length: usize,
    /// Enable pattern analysis and optimization
    pub enable_pattern_analysis: bool,
    /// Enable adaptive compilation thresholds
    pub enable_adaptive_thresholds: bool,
    /// Maximum cache size for compiled sequences
    pub max_cache_size: usize,
    /// Enable runtime profiling for optimization
    pub enable_runtime_profiling: bool,
    /// JIT compilation optimization level
    pub optimization_level: JITOptimizationLevel,
    /// Enable parallel compilation
    pub enable_parallel_compilation: bool,
}

impl Default for JITConfig {
    fn default() -> Self {
        Self {
            compilation_threshold: 10,
            max_sequence_length: 20,
            enable_pattern_analysis: true,
            enable_adaptive_thresholds: true,
            max_cache_size: 1000,
            enable_runtime_profiling: true,
            optimization_level: JITOptimizationLevel::Aggressive,
            enable_parallel_compilation: true,
        }
    }
}

/// JIT optimization levels
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum JITOptimizationLevel {
    /// No optimization
    None,
    /// Basic optimizations (constant folding, dead code elimination)
    Basic,
    /// Advanced optimizations (loop unrolling, vectorization)
    Advanced,
    /// Aggressive optimizations (inline expansion, specialized paths)
    Aggressive,
}

/// Gate sequence pattern for compilation
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct GateSequencePattern {
    /// Gate types in the sequence
    pub gate_types: Vec<InterfaceGateType>,
    /// Target qubits for each gate
    pub target_qubits: Vec<Vec<usize>>,
    /// Sequence hash for fast lookup
    pub hash: u64,
    /// Usage frequency
    pub frequency: usize,
    /// Last used timestamp
    pub last_used: Instant,
    /// Compilation status
    pub compilation_status: CompilationStatus,
}

impl Hash for GateSequencePattern {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.gate_types.hash(state);
        self.target_qubits.hash(state);
    }
}

/// Compilation status for gate sequences
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum CompilationStatus {
    /// Not yet compiled
    NotCompiled,
    /// Currently being compiled
    Compiling,
    /// Successfully compiled
    Compiled,
    /// Compilation failed
    Failed,
    /// Compiled and optimized
    Optimized,
}

/// Compiled gate sequence
#[derive(Debug, Clone)]
pub struct CompiledGateSequence {
    /// Original pattern
    pub pattern: GateSequencePattern,
    /// Compiled function pointer (simulation only)
    pub compiled_function: CompiledFunction,
    /// Compilation time
    pub compilation_time: Duration,
    /// Runtime performance statistics
    pub performance_stats: JITPerformanceStats,
    /// Memory usage
    pub memory_usage: usize,
    /// Optimization flags applied
    pub optimizations: Vec<JITOptimization>,
}

/// Compiled function representation
#[derive(Debug, Clone)]
pub enum CompiledFunction {
    /// Native machine code (placeholder for actual implementation)
    NativeCode {
        code_size: usize,
        entry_point: usize,
    },
    /// Optimized interpreter bytecode
    Bytecode {
        instructions: Vec<BytecodeInstruction>,
    },
    /// Specialized matrix operations
    MatrixOps { operations: Vec<MatrixOperation> },
    /// SIMD-optimized operations
    SIMDOps {
        vectorized_ops: Vec<VectorizedOperation>,
    },
}

/// JIT bytecode instructions
#[derive(Debug, Clone)]
pub enum BytecodeInstruction {
    /// Apply single-qubit gate
    ApplySingleQubit {
        gate_type: InterfaceGateType,
        target: usize,
    },
    /// Apply two-qubit gate
    ApplyTwoQubit {
        gate_type: InterfaceGateType,
        control: usize,
        target: usize,
    },
    /// Apply multi-qubit gate
    ApplyMultiQubit {
        gate_type: InterfaceGateType,
        targets: Vec<usize>,
    },
    /// Fused operation
    FusedOperation { operation: FusedGateOperation },
    /// Memory prefetch hint
    Prefetch { address_pattern: PrefetchPattern },
    /// Barrier/synchronization
    Barrier,
}

/// Matrix operation for compilation
#[derive(Debug, Clone)]
pub struct MatrixOperation {
    /// Operation type
    pub op_type: MatrixOpType,
    /// Target qubits
    pub targets: Vec<usize>,
    /// Matrix elements (if small enough to inline)
    pub matrix: Option<Array2<Complex64>>,
    /// Matrix computation function
    pub compute_matrix: MatrixComputeFunction,
}

/// Matrix operation types
#[derive(Debug, Clone)]
pub enum MatrixOpType {
    /// Direct matrix multiplication
    DirectMult,
    /// Kronecker product
    KroneckerProduct,
    /// Tensor contraction
    TensorContraction,
    /// Sparse matrix operation
    SparseOperation,
}

/// Matrix computation function
#[derive(Debug, Clone)]
pub enum MatrixComputeFunction {
    /// Precomputed matrix
    Precomputed(Array2<Complex64>),
    /// Runtime computation
    Runtime(String), // Function identifier
    /// Parameterized computation
    Parameterized {
        template: Array2<Complex64>,
        param_indices: Vec<usize>,
    },
}

/// Vectorized operation for SIMD
#[derive(Debug, Clone)]
pub struct VectorizedOperation {
    /// SIMD instruction type
    pub instruction: SIMDInstruction,
    /// Data layout requirements
    pub layout: SIMDLayout,
    /// Vector length
    pub vector_length: usize,
    /// Parallelization factor
    pub parallel_factor: usize,
}

/// SIMD instruction types
#[derive(Debug, Clone)]
pub enum SIMDInstruction {
    /// Vectorized complex multiplication
    ComplexMul,
    /// Vectorized complex addition
    ComplexAdd,
    /// Vectorized rotation
    Rotation,
    /// Vectorized tensor product
    TensorProduct,
    /// Vectorized gate application
    GateApplication,
}

/// SIMD data layout
#[derive(Debug, Clone)]
pub enum SIMDLayout {
    /// Array of structures (`AoS`)
    ArrayOfStructures,
    /// Structure of arrays (`SoA`)
    StructureOfArrays,
    /// Interleaved real/imaginary
    Interleaved,
    /// Separate real/imaginary arrays
    Separate,
}

/// Fused gate operation
#[derive(Debug, Clone)]
pub struct FusedGateOperation {
    /// Component gates
    pub gates: Vec<InterfaceGate>,
    /// Fused matrix
    pub fused_matrix: Array2<Complex64>,
    /// Target qubits for the fused operation
    pub targets: Vec<usize>,
    /// Optimization level applied
    pub optimization_level: JITOptimizationLevel,
}

/// Prefetch pattern for memory optimization
#[derive(Debug, Clone)]
pub enum PrefetchPattern {
    /// Sequential access
    Sequential { stride: usize },
    /// Strided access
    Strided { stride: usize, count: usize },
    /// Sparse access
    Sparse { indices: Vec<usize> },
    /// Block access
    Block { base: usize, size: usize },
}

/// JIT performance statistics
#[derive(Debug, Clone)]
pub struct JITPerformanceStats {
    /// Execution count
    pub execution_count: usize,
    /// Total execution time
    pub total_execution_time: Duration,
    /// Average execution time
    pub average_execution_time: Duration,
    /// Best execution time
    pub best_execution_time: Duration,
    /// Cache hit ratio
    pub cache_hit_ratio: f64,
    /// Memory bandwidth utilization
    pub memory_bandwidth: f64,
    /// CPU utilization
    pub cpu_utilization: f64,
    /// Performance improvement over interpreted
    pub speedup_factor: f64,
}

impl Default for JITPerformanceStats {
    fn default() -> Self {
        Self {
            execution_count: 0,
            total_execution_time: Duration::new(0, 0),
            average_execution_time: Duration::new(0, 0),
            best_execution_time: Duration::from_secs(u64::MAX),
            cache_hit_ratio: 0.0,
            memory_bandwidth: 0.0,
            cpu_utilization: 0.0,
            speedup_factor: 1.0,
        }
    }
}

/// JIT optimization techniques applied
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum JITOptimization {
    /// Constant folding
    ConstantFolding,
    /// Dead code elimination
    DeadCodeElimination,
    /// Loop unrolling
    LoopUnrolling,
    /// Vectorization
    Vectorization,
    /// Inline expansion
    InlineExpansion,
    /// Gate fusion
    GateFusion,
    /// Memory layout optimization
    MemoryLayoutOptimization,
    /// Instruction scheduling
    InstructionScheduling,
    /// Register allocation
    RegisterAllocation,
    /// Strength reduction
    StrengthReduction,
}

/// JIT compilation engine
pub struct JITCompiler {
    /// Configuration
    config: JITConfig,
    /// Pattern database
    patterns: Arc<RwLock<HashMap<u64, GateSequencePattern>>>,
    /// Compiled sequence cache
    compiled_cache: Arc<RwLock<HashMap<u64, CompiledGateSequence>>>,
    /// Pattern analyzer
    pattern_analyzer: Arc<Mutex<PatternAnalyzer>>,
    /// Runtime profiler
    profiler: Arc<Mutex<RuntimeProfiler>>,
    /// Compilation statistics
    stats: Arc<RwLock<JITCompilerStats>>,
}

impl JITCompiler {
    /// Create a new JIT compiler
    #[must_use]
    pub fn new(config: JITConfig) -> Self {
        Self {
            config,
            patterns: Arc::new(RwLock::new(HashMap::new())),
            compiled_cache: Arc::new(RwLock::new(HashMap::new())),
            pattern_analyzer: Arc::new(Mutex::new(PatternAnalyzer::new())),
            profiler: Arc::new(Mutex::new(RuntimeProfiler::new())),
            stats: Arc::new(RwLock::new(JITCompilerStats::default())),
        }
    }

    /// Analyze gate sequence and potentially compile
    pub fn analyze_sequence(&self, gates: &[InterfaceGate]) -> Result<Option<u64>> {
        if gates.len() > self.config.max_sequence_length {
            return Ok(None);
        }

        // Update patterns_analyzed counter
        {
            let mut stats = self
                .stats
                .write()
                .expect("JIT stats lock should not be poisoned");
            stats.patterns_analyzed += 1;
        }

        let pattern = Self::extract_pattern(gates)?;
        let pattern_hash = pattern.hash;

        // Update pattern frequency
        {
            let mut patterns = self
                .patterns
                .write()
                .expect("JIT patterns lock should not be poisoned");
            if let Some(existing_pattern) = patterns.get_mut(&pattern_hash) {
                existing_pattern.frequency += 1;
                existing_pattern.last_used = Instant::now();
            } else {
                patterns.insert(pattern_hash, pattern);
            }
        }

        // Check if compilation threshold is met (compile after threshold is exceeded)
        let should_compile = {
            let patterns = self
                .patterns
                .read()
                .expect("JIT patterns lock should not be poisoned");
            if let Some(pattern) = patterns.get(&pattern_hash) {
                pattern.frequency > self.config.compilation_threshold
                    && pattern.compilation_status == CompilationStatus::NotCompiled
            } else {
                false
            }
        };

        if should_compile {
            self.compile_sequence(pattern_hash)?;
        }

        Ok(Some(pattern_hash))
    }

    /// Extract pattern from gate sequence
    fn extract_pattern(gates: &[InterfaceGate]) -> Result<GateSequencePattern> {
        let mut gate_types = Vec::new();
        let mut target_qubits = Vec::new();

        for gate in gates {
            gate_types.push(gate.gate_type.clone());
            target_qubits.push(gate.qubits.clone());
        }

        let mut pattern = GateSequencePattern {
            gate_types,
            target_qubits,
            hash: 0,
            frequency: 1,
            last_used: Instant::now(),
            compilation_status: CompilationStatus::NotCompiled,
        };

        // Calculate hash
        use std::collections::hash_map::DefaultHasher;
        let mut hasher = DefaultHasher::new();
        pattern.hash(&mut hasher);
        pattern.hash = hasher.finish();

        Ok(pattern)
    }

    /// Compile a gate sequence pattern
    fn compile_sequence(&self, pattern_hash: u64) -> Result<()> {
        // Mark as compiling
        {
            let mut patterns = self
                .patterns
                .write()
                .expect("JIT patterns lock should not be poisoned");
            if let Some(pattern) = patterns.get_mut(&pattern_hash) {
                pattern.compilation_status = CompilationStatus::Compiling;
            }
        }

        let compilation_start = Instant::now();

        // Get pattern for compilation
        let pattern = {
            let patterns = self
                .patterns
                .read()
                .expect("JIT patterns lock should not be poisoned");
            patterns
                .get(&pattern_hash)
                .cloned()
                .ok_or_else(|| SimulatorError::InvalidParameter("Pattern not found".to_string()))?
        };

        // Perform compilation
        let compiled_function = self.perform_compilation(&pattern)?;
        let compilation_time = compilation_start.elapsed();

        // Create compiled sequence
        let compiled_sequence = CompiledGateSequence {
            pattern: pattern.clone(),
            compiled_function,
            compilation_time,
            performance_stats: JITPerformanceStats::default(),
            memory_usage: Self::estimate_memory_usage(&pattern),
            optimizations: self.apply_optimizations(&pattern)?,
        };

        // Store compiled sequence
        {
            let mut cache = self
                .compiled_cache
                .write()
                .expect("JIT cache lock should not be poisoned");
            cache.insert(pattern_hash, compiled_sequence);
        }

        // Update pattern status
        {
            let mut patterns = self
                .patterns
                .write()
                .expect("JIT patterns lock should not be poisoned");
            if let Some(pattern) = patterns.get_mut(&pattern_hash) {
                pattern.compilation_status = CompilationStatus::Compiled;
            }
        }

        // Update statistics
        {
            let mut stats = self
                .stats
                .write()
                .expect("JIT stats lock should not be poisoned");
            stats.total_compilations += 1;
            stats.total_compilation_time += compilation_time;
        }

        Ok(())
    }

    /// Perform the actual compilation
    fn perform_compilation(&self, pattern: &GateSequencePattern) -> Result<CompiledFunction> {
        match self.config.optimization_level {
            JITOptimizationLevel::None => Self::compile_basic(pattern),
            JITOptimizationLevel::Basic => self.compile_with_basic_optimizations(pattern),
            JITOptimizationLevel::Advanced => self.compile_with_advanced_optimizations(pattern),
            JITOptimizationLevel::Aggressive => self.compile_with_aggressive_optimizations(pattern),
        }
    }

    /// Basic compilation (bytecode generation)
    fn compile_basic(pattern: &GateSequencePattern) -> Result<CompiledFunction> {
        let mut instructions = Vec::new();

        for (i, gate_type) in pattern.gate_types.iter().enumerate() {
            let targets = &pattern.target_qubits[i];

            let instruction = match targets.len() {
                1 => BytecodeInstruction::ApplySingleQubit {
                    gate_type: gate_type.clone(),
                    target: targets[0],
                },
                2 => BytecodeInstruction::ApplyTwoQubit {
                    gate_type: gate_type.clone(),
                    control: targets[0],
                    target: targets[1],
                },
                _ => BytecodeInstruction::ApplyMultiQubit {
                    gate_type: gate_type.clone(),
                    targets: targets.clone(),
                },
            };

            instructions.push(instruction);
        }

        Ok(CompiledFunction::Bytecode { instructions })
    }

    /// Compilation with basic optimizations
    fn compile_with_basic_optimizations(
        &self,
        pattern: &GateSequencePattern,
    ) -> Result<CompiledFunction> {
        let mut bytecode = Self::compile_basic(pattern)?;

        if let CompiledFunction::Bytecode { instructions } = &mut bytecode {
            // Apply constant folding
            Self::apply_constant_folding(instructions)?;

            // Apply dead code elimination
            Self::apply_dead_code_elimination(instructions)?;
        }

        Ok(bytecode)
    }

    /// Compilation with advanced optimizations
    fn compile_with_advanced_optimizations(
        &self,
        pattern: &GateSequencePattern,
    ) -> Result<CompiledFunction> {
        let mut bytecode = self.compile_with_basic_optimizations(pattern)?;

        if let CompiledFunction::Bytecode { instructions } = &mut bytecode {
            // Apply loop unrolling
            self.apply_loop_unrolling(instructions)?;

            // Apply vectorization
            return Self::apply_vectorization(instructions);
        }

        Ok(bytecode)
    }

    /// Compilation with aggressive optimizations
    fn compile_with_aggressive_optimizations(
        &self,
        pattern: &GateSequencePattern,
    ) -> Result<CompiledFunction> {
        // First try advanced optimizations
        let advanced_result = self.compile_with_advanced_optimizations(pattern)?;

        // Apply aggressive optimizations
        match advanced_result {
            CompiledFunction::Bytecode { instructions } => {
                // Try to convert to optimized matrix operations
                if let Ok(matrix_ops) = self.convert_to_matrix_operations(&instructions) {
                    return Ok(CompiledFunction::MatrixOps {
                        operations: matrix_ops,
                    });
                }

                // Apply gate fusion
                if let Ok(fused_ops) = self.apply_gate_fusion(&instructions) {
                    return Ok(CompiledFunction::Bytecode {
                        instructions: fused_ops,
                    });
                }

                Ok(CompiledFunction::Bytecode { instructions })
            }
            other => Ok(other),
        }
    }

    /// Apply constant folding optimization
    fn apply_constant_folding(instructions: &mut [BytecodeInstruction]) -> Result<()> {
        // Constant folding for parameterized gates is now handled at the gate type level
        // Since parameters are embedded in the gate types, we can pre-compute
        // trigonometric functions and simplify zero rotations
        for instruction in instructions.iter_mut() {
            match instruction {
                BytecodeInstruction::ApplySingleQubit { gate_type, .. }
                | BytecodeInstruction::ApplyTwoQubit { gate_type, .. }
                | BytecodeInstruction::ApplyMultiQubit { gate_type, .. } => {
                    // Fold zero rotations to identity
                    match gate_type {
                        InterfaceGateType::RX(angle)
                        | InterfaceGateType::RY(angle)
                        | InterfaceGateType::RZ(angle)
                            if angle.abs() < f64::EPSILON =>
                        {
                            *gate_type = InterfaceGateType::Identity;
                        }
                        _ => {}
                    }
                }
                _ => {}
            }
        }
        Ok(())
    }

    /// Apply dead code elimination
    fn apply_dead_code_elimination(instructions: &mut Vec<BytecodeInstruction>) -> Result<()> {
        // Remove instructions that have no effect
        instructions.retain(|instruction| {
            match instruction {
                BytecodeInstruction::ApplySingleQubit { gate_type, .. } => {
                    // Remove identity operations
                    !matches!(gate_type, InterfaceGateType::Identity)
                }
                _ => true, // Keep all other instructions
            }
        });
        Ok(())
    }

    /// Apply loop unrolling optimization
    fn apply_loop_unrolling(&self, instructions: &mut Vec<BytecodeInstruction>) -> Result<()> {
        // Identify repeated patterns and unroll them
        let mut unrolled = Vec::new();
        let mut i = 0;

        while i < instructions.len() {
            // Look for repeated sequences
            if let Some(repeat_count) = Self::find_repeated_sequence(&instructions[i..]) {
                // Unroll the sequence
                for _ in 0..repeat_count {
                    unrolled.push(instructions[i].clone());
                }
                i += repeat_count;
            } else {
                unrolled.push(instructions[i].clone());
                i += 1;
            }
        }

        *instructions = unrolled;
        Ok(())
    }

    /// Find repeated instruction sequences
    fn find_repeated_sequence(instructions: &[BytecodeInstruction]) -> Option<usize> {
        if instructions.len() < 2 {
            return None;
        }

        // Simple pattern: look for immediate repetition
        if instructions.len() >= 2
            && std::mem::discriminant(&instructions[0]) == std::mem::discriminant(&instructions[1])
        {
            return Some(2);
        }

        None
    }

    /// Apply vectorization optimization
    fn apply_vectorization(instructions: &[BytecodeInstruction]) -> Result<CompiledFunction> {
        let mut vectorized_ops = Vec::new();

        for instruction in instructions {
            match instruction {
                BytecodeInstruction::ApplySingleQubit { gate_type, .. } => {
                    // Convert to SIMD operations where possible
                    let simd_instruction = match gate_type {
                        InterfaceGateType::PauliX
                        | InterfaceGateType::X
                        | InterfaceGateType::PauliY
                        | InterfaceGateType::PauliZ => SIMDInstruction::GateApplication,
                        InterfaceGateType::RX(_)
                        | InterfaceGateType::RY(_)
                        | InterfaceGateType::RZ(_) => SIMDInstruction::Rotation,
                        _ => SIMDInstruction::GateApplication,
                    };

                    vectorized_ops.push(VectorizedOperation {
                        instruction: simd_instruction,
                        layout: SIMDLayout::StructureOfArrays,
                        vector_length: 8, // AVX2 double precision
                        parallel_factor: 1,
                    });
                }
                _ => {
                    // Default vectorization
                    vectorized_ops.push(VectorizedOperation {
                        instruction: SIMDInstruction::GateApplication,
                        layout: SIMDLayout::Interleaved,
                        vector_length: 4,
                        parallel_factor: 1,
                    });
                }
            }
        }

        Ok(CompiledFunction::SIMDOps { vectorized_ops })
    }

    /// Convert bytecode to matrix operations
    fn convert_to_matrix_operations(
        &self,
        instructions: &[BytecodeInstruction],
    ) -> Result<Vec<MatrixOperation>> {
        let mut operations = Vec::new();

        for instruction in instructions {
            match instruction {
                BytecodeInstruction::ApplySingleQubit { gate_type, target } => {
                    let matrix = Self::get_gate_matrix(gate_type)?;
                    operations.push(MatrixOperation {
                        op_type: MatrixOpType::DirectMult,
                        targets: vec![*target],
                        matrix: Some(matrix),
                        compute_matrix: MatrixComputeFunction::Precomputed(Self::get_gate_matrix(
                            gate_type,
                        )?),
                    });
                }
                BytecodeInstruction::ApplyTwoQubit {
                    gate_type,
                    control,
                    target,
                } => {
                    let matrix = Self::get_two_qubit_gate_matrix(gate_type)?;
                    operations.push(MatrixOperation {
                        op_type: MatrixOpType::KroneckerProduct,
                        targets: vec![*control, *target],
                        matrix: Some(matrix),
                        compute_matrix: MatrixComputeFunction::Precomputed(
                            Self::get_two_qubit_gate_matrix(gate_type)?,
                        ),
                    });
                }
                _ => {
                    // Default to tensor contraction for complex operations
                    operations.push(MatrixOperation {
                        op_type: MatrixOpType::TensorContraction,
                        targets: vec![0], // Placeholder
                        matrix: None,
                        compute_matrix: MatrixComputeFunction::Runtime("default".to_string()),
                    });
                }
            }
        }

        Ok(operations)
    }

    /// Apply gate fusion optimization
    fn apply_gate_fusion(
        &self,
        instructions: &[BytecodeInstruction],
    ) -> Result<Vec<BytecodeInstruction>> {
        let mut fused_instructions = Vec::new();
        let mut i = 0;

        while i < instructions.len() {
            // Look for fusable gate sequences
            if let Some(fused_length) = Self::find_fusable_sequence(&instructions[i..]) {
                // Create fused operation
                let gates =
                    Self::extract_gates_from_instructions(&instructions[i..i + fused_length])?;
                let fused_matrix = Self::compute_fused_matrix(&gates)?;
                let targets =
                    Self::extract_targets_from_instructions(&instructions[i..i + fused_length]);

                let fused_op = FusedGateOperation {
                    gates,
                    fused_matrix,
                    targets,
                    optimization_level: self.config.optimization_level,
                };

                fused_instructions.push(BytecodeInstruction::FusedOperation {
                    operation: fused_op,
                });

                i += fused_length;
            } else {
                fused_instructions.push(instructions[i].clone());
                i += 1;
            }
        }

        Ok(fused_instructions)
    }

    /// Find fusable gate sequences
    fn find_fusable_sequence(instructions: &[BytecodeInstruction]) -> Option<usize> {
        if instructions.len() < 2 {
            return None;
        }

        // Look for consecutive single-qubit gates on the same target
        if let (
            BytecodeInstruction::ApplySingleQubit {
                target: target1, ..
            },
            BytecodeInstruction::ApplySingleQubit {
                target: target2, ..
            },
        ) = (&instructions[0], &instructions[1])
        {
            if target1 == target2 {
                return Some(2);
            }
        }

        None
    }

    /// Extract gates from bytecode instructions
    fn extract_gates_from_instructions(
        instructions: &[BytecodeInstruction],
    ) -> Result<Vec<InterfaceGate>> {
        let mut gates = Vec::new();

        for instruction in instructions {
            match instruction {
                BytecodeInstruction::ApplySingleQubit { gate_type, target } => {
                    gates.push(InterfaceGate::new(gate_type.clone(), vec![*target]));
                }
                BytecodeInstruction::ApplyTwoQubit {
                    gate_type,
                    control,
                    target,
                } => {
                    gates.push(InterfaceGate::new(
                        gate_type.clone(),
                        vec![*control, *target],
                    ));
                }
                BytecodeInstruction::ApplyMultiQubit { gate_type, targets } => {
                    gates.push(InterfaceGate::new(gate_type.clone(), targets.clone()));
                }
                _ => {
                    return Err(SimulatorError::NotImplemented(
                        "Complex gate extraction".to_string(),
                    ));
                }
            }
        }

        Ok(gates)
    }

    /// Extract target qubits from instructions
    fn extract_targets_from_instructions(instructions: &[BytecodeInstruction]) -> Vec<usize> {
        let mut targets = std::collections::HashSet::new();

        for instruction in instructions {
            match instruction {
                BytecodeInstruction::ApplySingleQubit { target, .. } => {
                    targets.insert(*target);
                }
                BytecodeInstruction::ApplyTwoQubit {
                    control, target, ..
                } => {
                    targets.insert(*control);
                    targets.insert(*target);
                }
                BytecodeInstruction::ApplyMultiQubit {
                    targets: multi_targets,
                    ..
                } => {
                    for &target in multi_targets {
                        targets.insert(target);
                    }
                }
                _ => {}
            }
        }

        targets.into_iter().collect()
    }

    /// Compute fused matrix for gate sequence
    fn compute_fused_matrix(gates: &[InterfaceGate]) -> Result<Array2<Complex64>> {
        if gates.is_empty() {
            return Err(SimulatorError::InvalidParameter(
                "Empty gate sequence".to_string(),
            ));
        }

        // Start with the first gate matrix
        let mut result = Self::get_gate_matrix(&gates[0].gate_type)?;

        // Multiply with subsequent gates
        for gate in &gates[1..] {
            let gate_matrix = Self::get_gate_matrix(&gate.gate_type)?;
            result = result.dot(&gate_matrix);
        }

        Ok(result)
    }

    /// Get matrix representation of a gate
    fn get_gate_matrix(gate_type: &InterfaceGateType) -> Result<Array2<Complex64>> {
        let matrix = match gate_type {
            InterfaceGateType::Identity => Array2::from_shape_vec(
                (2, 2),
                vec![
                    Complex64::new(1.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(1.0, 0.0),
                ],
            )
            .expect("2x2 matrix shape should be valid"),
            InterfaceGateType::PauliX | InterfaceGateType::X => Array2::from_shape_vec(
                (2, 2),
                vec![
                    Complex64::new(0.0, 0.0),
                    Complex64::new(1.0, 0.0),
                    Complex64::new(1.0, 0.0),
                    Complex64::new(0.0, 0.0),
                ],
            )
            .expect("2x2 matrix shape should be valid"),
            InterfaceGateType::PauliY => Array2::from_shape_vec(
                (2, 2),
                vec![
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, -1.0),
                    Complex64::new(0.0, 1.0),
                    Complex64::new(0.0, 0.0),
                ],
            )
            .expect("2x2 matrix shape should be valid"),
            InterfaceGateType::PauliZ => Array2::from_shape_vec(
                (2, 2),
                vec![
                    Complex64::new(1.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(-1.0, 0.0),
                ],
            )
            .expect("2x2 matrix shape should be valid"),
            InterfaceGateType::Hadamard | InterfaceGateType::H => {
                let sqrt2_inv = 1.0 / (2.0_f64).sqrt();
                Array2::from_shape_vec(
                    (2, 2),
                    vec![
                        Complex64::new(sqrt2_inv, 0.0),
                        Complex64::new(sqrt2_inv, 0.0),
                        Complex64::new(sqrt2_inv, 0.0),
                        Complex64::new(-sqrt2_inv, 0.0),
                    ],
                )
                .expect("2x2 matrix shape should be valid")
            }
            InterfaceGateType::S => Array2::from_shape_vec(
                (2, 2),
                vec![
                    Complex64::new(1.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 1.0),
                ],
            )
            .expect("2x2 matrix shape should be valid"),
            InterfaceGateType::T => {
                let phase = Complex64::new(0.0, std::f64::consts::PI / 4.0).exp();
                Array2::from_shape_vec(
                    (2, 2),
                    vec![
                        Complex64::new(1.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        phase,
                    ],
                )
                .expect("2x2 matrix shape should be valid")
            }
            InterfaceGateType::RX(angle) => {
                let cos_half = (angle / 2.0).cos();
                let sin_half = (angle / 2.0).sin();
                Array2::from_shape_vec(
                    (2, 2),
                    vec![
                        Complex64::new(cos_half, 0.0),
                        Complex64::new(0.0, -sin_half),
                        Complex64::new(0.0, -sin_half),
                        Complex64::new(cos_half, 0.0),
                    ],
                )
                .expect("2x2 matrix shape should be valid")
            }
            InterfaceGateType::RY(angle) => {
                let cos_half = (angle / 2.0).cos();
                let sin_half = (angle / 2.0).sin();
                Array2::from_shape_vec(
                    (2, 2),
                    vec![
                        Complex64::new(cos_half, 0.0),
                        Complex64::new(-sin_half, 0.0),
                        Complex64::new(sin_half, 0.0),
                        Complex64::new(cos_half, 0.0),
                    ],
                )
                .expect("2x2 matrix shape should be valid")
            }
            InterfaceGateType::RZ(angle) => {
                let exp_neg = Complex64::new(0.0, -angle / 2.0).exp();
                let exp_pos = Complex64::new(0.0, angle / 2.0).exp();
                Array2::from_shape_vec(
                    (2, 2),
                    vec![
                        exp_neg,
                        Complex64::new(0.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        exp_pos,
                    ],
                )
                .expect("2x2 matrix shape should be valid")
            }
            InterfaceGateType::Phase(angle) => {
                let phase = Complex64::new(0.0, *angle).exp();
                Array2::from_shape_vec(
                    (2, 2),
                    vec![
                        Complex64::new(1.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        phase,
                    ],
                )
                .expect("2x2 matrix shape should be valid")
            }
            _ => {
                // Default identity matrix for unknown gates
                Array2::from_shape_vec(
                    (2, 2),
                    vec![
                        Complex64::new(1.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        Complex64::new(1.0, 0.0),
                    ],
                )
                .expect("2x2 matrix shape should be valid")
            }
        };

        Ok(matrix)
    }

    /// Get matrix representation of a two-qubit gate
    fn get_two_qubit_gate_matrix(gate_type: &InterfaceGateType) -> Result<Array2<Complex64>> {
        let matrix = match gate_type {
            InterfaceGateType::CNOT => Array2::from_shape_vec(
                (4, 4),
                vec![
                    Complex64::new(1.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(1.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(1.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(1.0, 0.0),
                    Complex64::new(0.0, 0.0),
                ],
            )
            .expect("4x4 matrix shape should be valid"),
            InterfaceGateType::CZ => Array2::from_shape_vec(
                (4, 4),
                vec![
                    Complex64::new(1.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(1.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(1.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(-1.0, 0.0),
                ],
            )
            .expect("4x4 matrix shape should be valid"),
            InterfaceGateType::SWAP => Array2::from_shape_vec(
                (4, 4),
                vec![
                    Complex64::new(1.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(1.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(1.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(0.0, 0.0),
                    Complex64::new(1.0, 0.0),
                ],
            )
            .expect("4x4 matrix shape should be valid"),
            _ => {
                // Default identity matrix for unknown two-qubit gates
                Array2::from_shape_vec(
                    (4, 4),
                    vec![
                        Complex64::new(1.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        Complex64::new(1.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        Complex64::new(1.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        Complex64::new(0.0, 0.0),
                        Complex64::new(1.0, 0.0),
                    ],
                )
                .expect("4x4 matrix shape should be valid")
            }
        };

        Ok(matrix)
    }

    /// Estimate memory usage for a pattern
    fn estimate_memory_usage(pattern: &GateSequencePattern) -> usize {
        // Estimate based on pattern complexity
        let base_size = std::mem::size_of::<CompiledGateSequence>();
        let pattern_size = pattern.gate_types.len() * 64; // Rough estimate
        let matrix_size = pattern.gate_types.len() * 32 * std::mem::size_of::<Complex64>(); // 2x2 matrices

        base_size + pattern_size + matrix_size
    }

    /// Apply optimizations to a pattern
    fn apply_optimizations(&self, _pattern: &GateSequencePattern) -> Result<Vec<JITOptimization>> {
        let mut optimizations = vec![
            JITOptimization::ConstantFolding,
            JITOptimization::DeadCodeElimination,
        ];

        match self.config.optimization_level {
            JITOptimizationLevel::Basic => {
                // Basic optimizations already included
            }
            JITOptimizationLevel::Advanced => {
                optimizations.extend_from_slice(&[
                    JITOptimization::LoopUnrolling,
                    JITOptimization::Vectorization,
                ]);
            }
            JITOptimizationLevel::Aggressive => {
                optimizations.extend_from_slice(&[
                    JITOptimization::LoopUnrolling,
                    JITOptimization::Vectorization,
                    JITOptimization::GateFusion,
                    JITOptimization::InlineExpansion,
                    JITOptimization::MemoryLayoutOptimization,
                ]);
            }
            JITOptimizationLevel::None => {
                optimizations.clear();
            }
        }

        Ok(optimizations)
    }

    /// Execute a compiled sequence
    pub fn execute_compiled(
        &self,
        pattern_hash: u64,
        state: &mut Array1<Complex64>,
    ) -> Result<Duration> {
        let execution_start = Instant::now();

        let compiled_sequence = {
            let cache = self
                .compiled_cache
                .read()
                .expect("JIT cache lock should not be poisoned");
            cache.get(&pattern_hash).cloned().ok_or_else(|| {
                SimulatorError::InvalidParameter("Compiled sequence not found".to_string())
            })?
        };

        // Execute based on compilation type
        match &compiled_sequence.compiled_function {
            CompiledFunction::Bytecode { instructions } => {
                self.execute_bytecode(instructions, state)?;
            }
            CompiledFunction::MatrixOps { operations } => {
                self.execute_matrix_operations(operations, state)?;
            }
            CompiledFunction::SIMDOps { vectorized_ops } => {
                self.execute_simd_operations(vectorized_ops, state)?;
            }
            CompiledFunction::NativeCode { .. } => {
                // Native code execution would be implemented here
                return Err(SimulatorError::NotImplemented(
                    "Native code execution".to_string(),
                ));
            }
        }

        let execution_time = execution_start.elapsed();

        // Update performance statistics
        {
            let mut cache = self
                .compiled_cache
                .write()
                .expect("JIT cache lock should not be poisoned");
            if let Some(sequence) = cache.get_mut(&pattern_hash) {
                let stats = &mut sequence.performance_stats;
                stats.execution_count += 1;
                stats.total_execution_time += execution_time;
                stats.average_execution_time =
                    stats.total_execution_time / stats.execution_count as u32;
                if execution_time < stats.best_execution_time {
                    stats.best_execution_time = execution_time;
                }
            }
        }

        Ok(execution_time)
    }

    /// Execute bytecode instructions
    fn execute_bytecode(
        &self,
        instructions: &[BytecodeInstruction],
        state: &mut Array1<Complex64>,
    ) -> Result<()> {
        for instruction in instructions {
            match instruction {
                BytecodeInstruction::ApplySingleQubit { gate_type, target } => {
                    Self::apply_single_qubit_gate(gate_type, *target, state)?;
                }
                BytecodeInstruction::ApplyTwoQubit {
                    gate_type,
                    control,
                    target,
                } => {
                    Self::apply_two_qubit_gate(gate_type, *control, *target, state)?;
                }
                BytecodeInstruction::ApplyMultiQubit { gate_type, targets } => {
                    Self::apply_multi_qubit_gate(gate_type, targets, state)?;
                }
                BytecodeInstruction::FusedOperation { operation } => {
                    Self::apply_fused_operation(operation, state)?;
                }
                BytecodeInstruction::Prefetch { .. } => {
                    // Prefetch hints are processed during compilation
                }
                BytecodeInstruction::Barrier => {
                    // Memory barrier - ensure all previous operations complete
                    std::sync::atomic::fence(std::sync::atomic::Ordering::SeqCst);
                }
            }
        }
        Ok(())
    }

    /// Apply single-qubit gate to state
    fn apply_single_qubit_gate(
        gate_type: &InterfaceGateType,
        target: usize,
        state: &mut Array1<Complex64>,
    ) -> Result<()> {
        let num_qubits = (state.len() as f64).log2() as usize;
        if target >= num_qubits {
            return Err(SimulatorError::InvalidParameter(
                "Target qubit out of range".to_string(),
            ));
        }

        let matrix = Self::get_gate_matrix(gate_type)?;

        // Apply gate using matrix multiplication
        for i in 0..(1 << num_qubits) {
            if (i >> target) & 1 == 0 {
                let j = i | (1 << target);
                let amp0 = state[i];
                let amp1 = state[j];

                state[i] = matrix[(0, 0)] * amp0 + matrix[(0, 1)] * amp1;
                state[j] = matrix[(1, 0)] * amp0 + matrix[(1, 1)] * amp1;
            }
        }

        Ok(())
    }

    /// Apply two-qubit gate to state
    fn apply_two_qubit_gate(
        gate_type: &InterfaceGateType,
        control: usize,
        target: usize,
        state: &mut Array1<Complex64>,
    ) -> Result<()> {
        let num_qubits = (state.len() as f64).log2() as usize;
        if control >= num_qubits || target >= num_qubits {
            return Err(SimulatorError::InvalidParameter(
                "Qubit index out of range".to_string(),
            ));
        }

        match gate_type {
            InterfaceGateType::CNOT => {
                // CNOT implementation
                for i in 0..(1 << num_qubits) {
                    if (i >> control) & 1 == 1 {
                        let j = i ^ (1 << target);
                        if i < j {
                            let temp = state[i];
                            state[i] = state[j];
                            state[j] = temp;
                        }
                    }
                }
            }
            InterfaceGateType::CZ => {
                // CZ implementation
                for i in 0..(1 << num_qubits) {
                    if (i >> control) & 1 == 1 && (i >> target) & 1 == 1 {
                        state[i] = -state[i];
                    }
                }
            }
            InterfaceGateType::SWAP => {
                // SWAP implementation
                for i in 0..(1 << num_qubits) {
                    let bit_control = (i >> control) & 1;
                    let bit_target = (i >> target) & 1;
                    if bit_control != bit_target {
                        let j = i ^ (1 << control) ^ (1 << target);
                        if i < j {
                            let temp = state[i];
                            state[i] = state[j];
                            state[j] = temp;
                        }
                    }
                }
            }
            _ => {
                // Use full matrix for unknown gates
                let matrix = Self::get_two_qubit_gate_matrix(gate_type)?;
                Self::apply_two_qubit_matrix(&matrix, control, target, state)?;
            }
        }

        Ok(())
    }

    /// Apply multi-qubit gate to state
    fn apply_multi_qubit_gate(
        _gate_type: &InterfaceGateType,
        _targets: &[usize],
        _state: &mut Array1<Complex64>,
    ) -> Result<()> {
        // Multi-qubit gate implementation would go here
        Err(SimulatorError::NotImplemented(
            "Multi-qubit gate execution".to_string(),
        ))
    }

    /// Apply fused operation to state
    fn apply_fused_operation(
        operation: &FusedGateOperation,
        state: &mut Array1<Complex64>,
    ) -> Result<()> {
        // Apply the pre-computed fused matrix
        if operation.targets.len() == 1 {
            let target = operation.targets[0];
            let num_qubits = (state.len() as f64).log2() as usize;

            for i in 0..(1 << num_qubits) {
                if (i >> target) & 1 == 0 {
                    let j = i | (1 << target);
                    let amp0 = state[i];
                    let amp1 = state[j];

                    state[i] = operation.fused_matrix[(0, 0)] * amp0
                        + operation.fused_matrix[(0, 1)] * amp1;
                    state[j] = operation.fused_matrix[(1, 0)] * amp0
                        + operation.fused_matrix[(1, 1)] * amp1;
                }
            }
        }

        Ok(())
    }

    /// Execute matrix operations
    fn execute_matrix_operations(
        &self,
        operations: &[MatrixOperation],
        state: &mut Array1<Complex64>,
    ) -> Result<()> {
        for operation in operations {
            match &operation.op_type {
                MatrixOpType::DirectMult => {
                    if let Some(matrix) = &operation.matrix {
                        // Apply matrix directly
                        for &target in &operation.targets {
                            Self::apply_matrix_to_target(matrix, target, state)?;
                        }
                    }
                }
                MatrixOpType::KroneckerProduct => {
                    // Apply Kronecker product operation
                    if operation.targets.len() == 2 && operation.matrix.is_some() {
                        let control = operation.targets[0];
                        let target = operation.targets[1];
                        Self::apply_two_qubit_matrix(
                            operation
                                .matrix
                                .as_ref()
                                .expect("matrix should exist after is_some check"),
                            control,
                            target,
                            state,
                        )?;
                    }
                }
                _ => {
                    return Err(SimulatorError::NotImplemented(
                        "Matrix operation type".to_string(),
                    ));
                }
            }
        }
        Ok(())
    }

    /// Apply matrix to specific target qubit
    fn apply_matrix_to_target(
        matrix: &Array2<Complex64>,
        target: usize,
        state: &mut Array1<Complex64>,
    ) -> Result<()> {
        let num_qubits = (state.len() as f64).log2() as usize;
        if target >= num_qubits {
            return Err(SimulatorError::InvalidParameter(
                "Target qubit out of range".to_string(),
            ));
        }

        for i in 0..(1 << num_qubits) {
            if (i >> target) & 1 == 0 {
                let j = i | (1 << target);
                let amp0 = state[i];
                let amp1 = state[j];

                state[i] = matrix[(0, 0)] * amp0 + matrix[(0, 1)] * amp1;
                state[j] = matrix[(1, 0)] * amp0 + matrix[(1, 1)] * amp1;
            }
        }

        Ok(())
    }

    /// Apply two-qubit matrix
    fn apply_two_qubit_matrix(
        matrix: &Array2<Complex64>,
        control: usize,
        target: usize,
        state: &mut Array1<Complex64>,
    ) -> Result<()> {
        let num_qubits = (state.len() as f64).log2() as usize;
        if control >= num_qubits || target >= num_qubits {
            return Err(SimulatorError::InvalidParameter(
                "Qubit index out of range".to_string(),
            ));
        }

        // Apply 4x4 matrix to two-qubit subspace
        for i in 0..(1 << num_qubits) {
            let control_bit = (i >> control) & 1;
            let target_bit = (i >> target) & 1;
            let basis_state = control_bit * 2 + target_bit;

            if basis_state == 0 {
                // Find all four computational basis states
                let i00 = i;
                let i01 = i ^ (1 << target);
                let i10 = i ^ (1 << control);
                let i11 = i ^ (1 << control) ^ (1 << target);

                let amp00 = state[i00];
                let amp01 = state[i01];
                let amp10 = state[i10];
                let amp11 = state[i11];

                state[i00] = matrix[(0, 0)] * amp00
                    + matrix[(0, 1)] * amp01
                    + matrix[(0, 2)] * amp10
                    + matrix[(0, 3)] * amp11;
                state[i01] = matrix[(1, 0)] * amp00
                    + matrix[(1, 1)] * amp01
                    + matrix[(1, 2)] * amp10
                    + matrix[(1, 3)] * amp11;
                state[i10] = matrix[(2, 0)] * amp00
                    + matrix[(2, 1)] * amp01
                    + matrix[(2, 2)] * amp10
                    + matrix[(2, 3)] * amp11;
                state[i11] = matrix[(3, 0)] * amp00
                    + matrix[(3, 1)] * amp01
                    + matrix[(3, 2)] * amp10
                    + matrix[(3, 3)] * amp11;
            }
        }

        Ok(())
    }

    /// Execute SIMD operations
    fn execute_simd_operations(
        &self,
        operations: &[VectorizedOperation],
        state: &mut Array1<Complex64>,
    ) -> Result<()> {
        // SIMD execution would leverage architecture-specific optimizations
        for operation in operations {
            match operation.instruction {
                SIMDInstruction::ComplexMul => {
                    Self::execute_simd_complex_mul(operation, state)?;
                }
                SIMDInstruction::ComplexAdd => {
                    Self::execute_simd_complex_add(operation, state)?;
                }
                SIMDInstruction::Rotation => {
                    Self::execute_simd_rotation(operation, state)?;
                }
                SIMDInstruction::GateApplication => {
                    Self::execute_simd_gate_application(operation, state)?;
                }
                SIMDInstruction::TensorProduct => {
                    return Err(SimulatorError::NotImplemented(
                        "SIMD instruction".to_string(),
                    ));
                }
            }
        }
        Ok(())
    }

    /// Execute SIMD complex multiplication
    fn execute_simd_complex_mul(
        _operation: &VectorizedOperation,
        _state: &mut Array1<Complex64>,
    ) -> Result<()> {
        // SIMD complex multiplication implementation
        Ok(())
    }

    /// Execute SIMD complex addition
    fn execute_simd_complex_add(
        _operation: &VectorizedOperation,
        _state: &mut Array1<Complex64>,
    ) -> Result<()> {
        // SIMD complex addition implementation
        Ok(())
    }

    /// Execute SIMD rotation
    fn execute_simd_rotation(
        _operation: &VectorizedOperation,
        _state: &mut Array1<Complex64>,
    ) -> Result<()> {
        // SIMD rotation implementation
        Ok(())
    }

    /// Execute SIMD gate application
    fn execute_simd_gate_application(
        _operation: &VectorizedOperation,
        _state: &mut Array1<Complex64>,
    ) -> Result<()> {
        // SIMD gate application implementation
        Ok(())
    }

    /// Get compilation statistics
    #[must_use]
    pub fn get_stats(&self) -> JITCompilerStats {
        self.stats
            .read()
            .expect("JIT stats lock should not be poisoned")
            .clone()
    }

    /// Clear compiled cache
    pub fn clear_cache(&self) {
        let mut cache = self
            .compiled_cache
            .write()
            .expect("JIT cache lock should not be poisoned");
        cache.clear();

        let mut stats = self
            .stats
            .write()
            .expect("JIT stats lock should not be poisoned");
        stats.cache_clears += 1;
    }
}

/// Pattern analyzer for detecting common gate sequences
pub struct PatternAnalyzer {
    /// Pattern frequency tracking
    pattern_frequencies: HashMap<String, usize>,
    /// Pattern complexity analysis
    complexity_analyzer: ComplexityAnalyzer,
    /// Pattern optimization suggestions
    optimization_suggestions: Vec<OptimizationSuggestion>,
}

impl Default for PatternAnalyzer {
    fn default() -> Self {
        Self::new()
    }
}

impl PatternAnalyzer {
    #[must_use]
    pub fn new() -> Self {
        Self {
            pattern_frequencies: HashMap::new(),
            complexity_analyzer: ComplexityAnalyzer::new(),
            optimization_suggestions: Vec::new(),
        }
    }

    /// Analyze gate sequence for patterns
    pub fn analyze_pattern(&mut self, gates: &[InterfaceGate]) -> PatternAnalysisResult {
        let pattern_signature = Self::compute_pattern_signature(gates);

        // Update frequency
        *self
            .pattern_frequencies
            .entry(pattern_signature.clone())
            .or_insert(0) += 1;

        // Analyze complexity
        let complexity = self.complexity_analyzer.analyze_complexity(gates);

        // Generate optimization suggestions
        let suggestions = self.generate_optimization_suggestions(gates, &complexity);

        let frequency = self.pattern_frequencies[&pattern_signature];

        PatternAnalysisResult {
            pattern_signature,
            frequency,
            complexity,
            optimization_suggestions: suggestions,
            compilation_priority: self.compute_compilation_priority(gates),
        }
    }

    /// Compute pattern signature
    fn compute_pattern_signature(gates: &[InterfaceGate]) -> String {
        gates
            .iter()
            .map(|gate| format!("{:?}", gate.gate_type))
            .collect::<Vec<_>>()
            .join("-")
    }

    /// Generate optimization suggestions
    fn generate_optimization_suggestions(
        &self,
        gates: &[InterfaceGate],
        complexity: &PatternComplexity,
    ) -> Vec<OptimizationSuggestion> {
        let mut suggestions = Vec::new();

        // Check for fusion opportunities
        if Self::can_fuse_gates(gates) {
            suggestions.push(OptimizationSuggestion::GateFusion);
        }

        // Check for vectorization opportunities
        if complexity.parallelizable_operations > 0 {
            suggestions.push(OptimizationSuggestion::Vectorization);
        }

        // Check for constant folding opportunities
        if complexity.constant_operations > 0 {
            suggestions.push(OptimizationSuggestion::ConstantFolding);
        }

        suggestions
    }

    /// Check if gates can be fused
    fn can_fuse_gates(gates: &[InterfaceGate]) -> bool {
        if gates.len() < 2 {
            return false;
        }

        // Check for consecutive single-qubit gates on same target
        for window in gates.windows(2) {
            if window[0].qubits.len() == 1
                && window[1].qubits.len() == 1
                && window[0].qubits[0] == window[1].qubits[0]
            {
                return true;
            }
        }

        false
    }

    /// Compute compilation priority
    fn compute_compilation_priority(&self, gates: &[InterfaceGate]) -> CompilationPriority {
        let length = gates.len();
        let complexity = self.complexity_analyzer.analyze_complexity(gates);

        if length > 10 && complexity.computational_cost > 100.0 {
            CompilationPriority::High
        } else if length > 5 && complexity.computational_cost > 50.0 {
            CompilationPriority::Medium
        } else {
            CompilationPriority::Low
        }
    }
}

/// Pattern analysis result
#[derive(Debug, Clone)]
pub struct PatternAnalysisResult {
    /// Pattern signature
    pub pattern_signature: String,
    /// Usage frequency
    pub frequency: usize,
    /// Pattern complexity analysis
    pub complexity: PatternComplexity,
    /// Optimization suggestions
    pub optimization_suggestions: Vec<OptimizationSuggestion>,
    /// Compilation priority
    pub compilation_priority: CompilationPriority,
}

/// Pattern complexity analysis
#[derive(Debug, Clone)]
pub struct PatternComplexity {
    /// Number of gates in pattern
    pub gate_count: usize,
    /// Computational cost estimate
    pub computational_cost: f64,
    /// Memory usage estimate
    pub memory_usage: usize,
    /// Number of parallelizable operations
    pub parallelizable_operations: usize,
    /// Number of constant operations
    pub constant_operations: usize,
    /// Critical path length
    pub critical_path_length: usize,
}

/// Complexity analyzer
pub struct ComplexityAnalyzer {
    /// Gate cost database
    gate_costs: HashMap<InterfaceGateType, f64>,
}

impl Default for ComplexityAnalyzer {
    fn default() -> Self {
        Self::new()
    }
}

impl ComplexityAnalyzer {
    #[must_use]
    pub fn new() -> Self {
        let mut gate_costs = HashMap::new();

        // Initialize gate costs (relative computational complexity)
        gate_costs.insert(InterfaceGateType::PauliX, 1.0);
        gate_costs.insert(InterfaceGateType::PauliY, 1.0);
        gate_costs.insert(InterfaceGateType::PauliZ, 1.0);
        gate_costs.insert(InterfaceGateType::Hadamard, 2.0);
        gate_costs.insert(InterfaceGateType::CNOT, 10.0);

        Self { gate_costs }
    }

    /// Analyze pattern complexity
    #[must_use]
    pub fn analyze_complexity(&self, gates: &[InterfaceGate]) -> PatternComplexity {
        let gate_count = gates.len();
        let computational_cost = self.compute_computational_cost(gates);
        let memory_usage = Self::estimate_memory_usage(gates);
        let parallelizable_operations = Self::count_parallelizable_operations(gates);
        let constant_operations = Self::count_constant_operations(gates);
        let critical_path_length = Self::compute_critical_path_length(gates);

        PatternComplexity {
            gate_count,
            computational_cost,
            memory_usage,
            parallelizable_operations,
            constant_operations,
            critical_path_length,
        }
    }

    /// Compute computational cost
    fn compute_computational_cost(&self, gates: &[InterfaceGate]) -> f64 {
        gates
            .iter()
            .map(|gate| {
                // Handle parameterized gates
                match &gate.gate_type {
                    InterfaceGateType::RX(_)
                    | InterfaceGateType::RY(_)
                    | InterfaceGateType::RZ(_) => 5.0,
                    InterfaceGateType::Phase(_) => 3.0,
                    InterfaceGateType::U1(_) => 4.0,
                    InterfaceGateType::U2(_, _) => 6.0,
                    InterfaceGateType::U3(_, _, _) => 8.0,
                    InterfaceGateType::CRX(_)
                    | InterfaceGateType::CRY(_)
                    | InterfaceGateType::CRZ(_)
                    | InterfaceGateType::CPhase(_) => 12.0,
                    _ => self.gate_costs.get(&gate.gate_type).copied().unwrap_or(1.0),
                }
            })
            .sum()
    }

    /// Estimate memory usage
    fn estimate_memory_usage(gates: &[InterfaceGate]) -> usize {
        // Rough estimate based on gate count and types
        gates.len() * 32 + gates.iter().map(|g| g.qubits.len() * 8).sum::<usize>()
    }

    /// Count parallelizable operations
    fn count_parallelizable_operations(gates: &[InterfaceGate]) -> usize {
        // Operations that don't share targets can be parallelized
        let mut parallelizable = 0;
        let mut used_qubits = std::collections::HashSet::new();

        for gate in gates {
            let mut can_parallelize = true;
            for &target in &gate.qubits {
                if used_qubits.contains(&target) {
                    can_parallelize = false;
                    break;
                }
            }

            if can_parallelize {
                parallelizable += 1;
                for &target in &gate.qubits {
                    used_qubits.insert(target);
                }
            } else {
                used_qubits.clear();
                for &target in &gate.qubits {
                    used_qubits.insert(target);
                }
            }
        }

        parallelizable
    }

    /// Count constant operations
    fn count_constant_operations(gates: &[InterfaceGate]) -> usize {
        gates
            .iter()
            .filter(|gate| {
                // Operations with constant parameters can be optimized
                match &gate.gate_type {
                    InterfaceGateType::RX(angle)
                    | InterfaceGateType::RY(angle)
                    | InterfaceGateType::RZ(angle)
                    | InterfaceGateType::Phase(angle) => {
                        angle.abs() < f64::EPSILON
                            || (angle - std::f64::consts::PI).abs() < f64::EPSILON
                    }
                    _ => true, // Non-parameterized gates are considered constant
                }
            })
            .count()
    }

    /// Compute critical path length
    fn compute_critical_path_length(gates: &[InterfaceGate]) -> usize {
        // Simple heuristic: maximum depth of dependency chain
        let mut qubit_depths = HashMap::new();
        let mut max_depth = 0;

        for gate in gates {
            let mut current_depth = 0;
            for &target in &gate.qubits {
                if let Some(&depth) = qubit_depths.get(&target) {
                    current_depth = current_depth.max(depth);
                }
            }
            current_depth += 1;

            for &target in &gate.qubits {
                qubit_depths.insert(target, current_depth);
            }

            max_depth = max_depth.max(current_depth);
        }

        max_depth
    }
}

/// Optimization suggestions
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum OptimizationSuggestion {
    /// Gate fusion optimization
    GateFusion,
    /// Vectorization optimization
    Vectorization,
    /// Constant folding optimization
    ConstantFolding,
    /// Loop unrolling optimization
    LoopUnrolling,
    /// Memory layout optimization
    MemoryLayoutOptimization,
    /// Instruction scheduling optimization
    InstructionScheduling,
}

/// Compilation priority levels
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum CompilationPriority {
    /// Low priority
    Low,
    /// Medium priority
    Medium,
    /// High priority
    High,
    /// Critical priority
    Critical,
}

/// Runtime profiler for performance monitoring
pub struct RuntimeProfiler {
    /// Execution time tracking
    execution_times: VecDeque<Duration>,
    /// Memory usage tracking
    memory_usage: VecDeque<usize>,
    /// Performance statistics
    stats: RuntimeProfilerStats,
}

impl Default for RuntimeProfiler {
    fn default() -> Self {
        Self::new()
    }
}

impl RuntimeProfiler {
    #[must_use]
    pub fn new() -> Self {
        Self {
            execution_times: VecDeque::new(),
            memory_usage: VecDeque::new(),
            stats: RuntimeProfilerStats::default(),
        }
    }

    /// Record execution time
    pub fn record_execution_time(&mut self, duration: Duration) {
        self.execution_times.push_back(duration);
        if self.execution_times.len() > 1000 {
            self.execution_times.pop_front();
        }
        self.update_stats();
    }

    /// Record memory usage
    pub fn record_memory_usage(&mut self, usage: usize) {
        self.memory_usage.push_back(usage);
        if self.memory_usage.len() > 1000 {
            self.memory_usage.pop_front();
        }
        self.update_stats();
    }

    /// Update performance statistics
    fn update_stats(&mut self) {
        if !self.execution_times.is_empty() {
            let total_time: Duration = self.execution_times.iter().sum();
            self.stats.average_execution_time = total_time / self.execution_times.len() as u32;

            self.stats.min_execution_time = self
                .execution_times
                .iter()
                .min()
                .copied()
                .unwrap_or(Duration::from_secs(0));
            self.stats.max_execution_time = self
                .execution_times
                .iter()
                .max()
                .copied()
                .unwrap_or(Duration::from_secs(0));
        }

        if !self.memory_usage.is_empty() {
            self.stats.average_memory_usage =
                self.memory_usage.iter().sum::<usize>() / self.memory_usage.len();
            self.stats.peak_memory_usage = self.memory_usage.iter().max().copied().unwrap_or(0);
        }

        self.stats.sample_count = self.execution_times.len();
    }

    /// Get current statistics
    #[must_use]
    pub const fn get_stats(&self) -> &RuntimeProfilerStats {
        &self.stats
    }
}

/// Runtime profiler statistics
#[derive(Debug, Clone)]
pub struct RuntimeProfilerStats {
    /// Average execution time
    pub average_execution_time: Duration,
    /// Minimum execution time
    pub min_execution_time: Duration,
    /// Maximum execution time
    pub max_execution_time: Duration,
    /// Average memory usage
    pub average_memory_usage: usize,
    /// Peak memory usage
    pub peak_memory_usage: usize,
    /// Number of samples
    pub sample_count: usize,
}

impl Default for RuntimeProfilerStats {
    fn default() -> Self {
        Self {
            average_execution_time: Duration::from_secs(0),
            min_execution_time: Duration::from_secs(0),
            max_execution_time: Duration::from_secs(0),
            average_memory_usage: 0,
            peak_memory_usage: 0,
            sample_count: 0,
        }
    }
}

/// JIT compiler statistics
#[derive(Debug, Clone)]
pub struct JITCompilerStats {
    /// Total number of compilations
    pub total_compilations: usize,
    /// Total compilation time
    pub total_compilation_time: Duration,
    /// Number of cache hits
    pub cache_hits: usize,
    /// Number of cache misses
    pub cache_misses: usize,
    /// Number of cache clears
    pub cache_clears: usize,
    /// Average compilation time
    pub average_compilation_time: Duration,
    /// Total patterns analyzed
    pub patterns_analyzed: usize,
    /// Successful compilations
    pub successful_compilations: usize,
    /// Failed compilations
    pub failed_compilations: usize,
}

impl Default for JITCompilerStats {
    fn default() -> Self {
        Self {
            total_compilations: 0,
            total_compilation_time: Duration::from_secs(0),
            cache_hits: 0,
            cache_misses: 0,
            cache_clears: 0,
            average_compilation_time: Duration::from_secs(0),
            patterns_analyzed: 0,
            successful_compilations: 0,
            failed_compilations: 0,
        }
    }
}

/// JIT-enabled quantum simulator
pub struct JITQuantumSimulator {
    /// State vector
    state: Array1<Complex64>,
    /// Number of qubits
    num_qubits: usize,
    /// JIT compiler
    compiler: JITCompiler,
    /// Execution statistics
    stats: JITSimulatorStats,
}

impl JITQuantumSimulator {
    /// Create new JIT-enabled simulator
    #[must_use]
    pub fn new(num_qubits: usize, config: JITConfig) -> Self {
        let state_size = 1 << num_qubits;
        let mut state = Array1::zeros(state_size);
        state[0] = Complex64::new(1.0, 0.0); // |0...0⟩ state

        Self {
            state,
            num_qubits,
            compiler: JITCompiler::new(config),
            stats: JITSimulatorStats::default(),
        }
    }

    /// Apply gate sequence with JIT optimization
    pub fn apply_gate_sequence(&mut self, gates: &[InterfaceGate]) -> Result<Duration> {
        let execution_start = Instant::now();

        // Analyze sequence for compilation opportunities
        if let Some(pattern_hash) = self.compiler.analyze_sequence(gates)? {
            // Check if compiled version exists
            if self.is_compiled(pattern_hash) {
                // Execute compiled version
                let exec_time = self
                    .compiler
                    .execute_compiled(pattern_hash, &mut self.state)?;
                self.stats.compiled_executions += 1;
                self.stats.total_compiled_time += exec_time;
                return Ok(exec_time);
            }
        }

        // Fall back to interpreted execution
        for gate in gates {
            self.apply_gate_interpreted(gate)?;
        }

        let execution_time = execution_start.elapsed();
        self.stats.interpreted_executions += 1;
        self.stats.total_interpreted_time += execution_time;

        Ok(execution_time)
    }

    /// Check if pattern is compiled
    fn is_compiled(&self, pattern_hash: u64) -> bool {
        let cache = self
            .compiler
            .compiled_cache
            .read()
            .expect("JIT cache lock should not be poisoned");
        cache.contains_key(&pattern_hash)
    }

    /// Apply single gate in interpreted mode
    fn apply_gate_interpreted(&mut self, gate: &InterfaceGate) -> Result<()> {
        match &gate.gate_type {
            InterfaceGateType::PauliX | InterfaceGateType::X => {
                if gate.qubits.len() != 1 {
                    return Err(SimulatorError::InvalidParameter(
                        "Pauli-X requires exactly one target".to_string(),
                    ));
                }
                self.apply_pauli_x(gate.qubits[0])
            }
            InterfaceGateType::PauliY => {
                if gate.qubits.len() != 1 {
                    return Err(SimulatorError::InvalidParameter(
                        "Pauli-Y requires exactly one target".to_string(),
                    ));
                }
                self.apply_pauli_y(gate.qubits[0])
            }
            InterfaceGateType::PauliZ => {
                if gate.qubits.len() != 1 {
                    return Err(SimulatorError::InvalidParameter(
                        "Pauli-Z requires exactly one target".to_string(),
                    ));
                }
                self.apply_pauli_z(gate.qubits[0])
            }
            InterfaceGateType::Hadamard | InterfaceGateType::H => {
                if gate.qubits.len() != 1 {
                    return Err(SimulatorError::InvalidParameter(
                        "Hadamard requires exactly one target".to_string(),
                    ));
                }
                self.apply_hadamard(gate.qubits[0])
            }
            InterfaceGateType::CNOT => {
                if gate.qubits.len() != 2 {
                    return Err(SimulatorError::InvalidParameter(
                        "CNOT requires exactly two targets".to_string(),
                    ));
                }
                self.apply_cnot(gate.qubits[0], gate.qubits[1])
            }
            InterfaceGateType::RX(angle) => {
                if gate.qubits.len() != 1 {
                    return Err(SimulatorError::InvalidParameter(
                        "RX requires one target".to_string(),
                    ));
                }
                self.apply_rx(gate.qubits[0], *angle)
            }
            InterfaceGateType::RY(angle) => {
                if gate.qubits.len() != 1 {
                    return Err(SimulatorError::InvalidParameter(
                        "RY requires one target".to_string(),
                    ));
                }
                self.apply_ry(gate.qubits[0], *angle)
            }
            InterfaceGateType::RZ(angle) => {
                if gate.qubits.len() != 1 {
                    return Err(SimulatorError::InvalidParameter(
                        "RZ requires one target".to_string(),
                    ));
                }
                self.apply_rz(gate.qubits[0], *angle)
            }
            _ => Err(SimulatorError::NotImplemented(format!(
                "Gate type {:?}",
                gate.gate_type
            ))),
        }
    }

    /// Apply Pauli-X gate
    fn apply_pauli_x(&mut self, target: usize) -> Result<()> {
        if target >= self.num_qubits {
            return Err(SimulatorError::InvalidParameter(
                "Target qubit out of range".to_string(),
            ));
        }

        for i in 0..(1 << self.num_qubits) {
            let j = i ^ (1 << target);
            if i < j {
                let temp = self.state[i];
                self.state[i] = self.state[j];
                self.state[j] = temp;
            }
        }

        Ok(())
    }

    /// Apply Pauli-Y gate
    fn apply_pauli_y(&mut self, target: usize) -> Result<()> {
        if target >= self.num_qubits {
            return Err(SimulatorError::InvalidParameter(
                "Target qubit out of range".to_string(),
            ));
        }

        for i in 0..(1 << self.num_qubits) {
            if (i >> target) & 1 == 0 {
                let j = i | (1 << target);
                let temp = self.state[i];
                self.state[i] = Complex64::new(0.0, 1.0) * self.state[j];
                self.state[j] = Complex64::new(0.0, -1.0) * temp;
            }
        }

        Ok(())
    }

    /// Apply Pauli-Z gate
    fn apply_pauli_z(&mut self, target: usize) -> Result<()> {
        if target >= self.num_qubits {
            return Err(SimulatorError::InvalidParameter(
                "Target qubit out of range".to_string(),
            ));
        }

        for i in 0..(1 << self.num_qubits) {
            if (i >> target) & 1 == 1 {
                self.state[i] = -self.state[i];
            }
        }

        Ok(())
    }

    /// Apply Hadamard gate
    fn apply_hadamard(&mut self, target: usize) -> Result<()> {
        if target >= self.num_qubits {
            return Err(SimulatorError::InvalidParameter(
                "Target qubit out of range".to_string(),
            ));
        }

        let sqrt2_inv = 1.0 / (2.0_f64).sqrt();

        for i in 0..(1 << self.num_qubits) {
            if (i >> target) & 1 == 0 {
                let j = i | (1 << target);
                let amp0 = self.state[i];
                let amp1 = self.state[j];

                self.state[i] = sqrt2_inv * (amp0 + amp1);
                self.state[j] = sqrt2_inv * (amp0 - amp1);
            }
        }

        Ok(())
    }

    /// Apply CNOT gate
    fn apply_cnot(&mut self, control: usize, target: usize) -> Result<()> {
        if control >= self.num_qubits || target >= self.num_qubits {
            return Err(SimulatorError::InvalidParameter(
                "Qubit index out of range".to_string(),
            ));
        }

        for i in 0..(1 << self.num_qubits) {
            if (i >> control) & 1 == 1 {
                let j = i ^ (1 << target);
                if i < j {
                    let temp = self.state[i];
                    self.state[i] = self.state[j];
                    self.state[j] = temp;
                }
            }
        }

        Ok(())
    }

    /// Apply RX gate
    fn apply_rx(&mut self, target: usize, angle: f64) -> Result<()> {
        if target >= self.num_qubits {
            return Err(SimulatorError::InvalidParameter(
                "Target qubit out of range".to_string(),
            ));
        }

        let cos_half = (angle / 2.0).cos();
        let sin_half = (angle / 2.0).sin();

        for i in 0..(1 << self.num_qubits) {
            if (i >> target) & 1 == 0 {
                let j = i | (1 << target);
                let amp0 = self.state[i];
                let amp1 = self.state[j];

                self.state[i] = cos_half * amp0 - Complex64::new(0.0, sin_half) * amp1;
                self.state[j] = -Complex64::new(0.0, sin_half) * amp0 + cos_half * amp1;
            }
        }

        Ok(())
    }

    /// Apply RY gate
    fn apply_ry(&mut self, target: usize, angle: f64) -> Result<()> {
        if target >= self.num_qubits {
            return Err(SimulatorError::InvalidParameter(
                "Target qubit out of range".to_string(),
            ));
        }

        let cos_half = (angle / 2.0).cos();
        let sin_half = (angle / 2.0).sin();

        for i in 0..(1 << self.num_qubits) {
            if (i >> target) & 1 == 0 {
                let j = i | (1 << target);
                let amp0 = self.state[i];
                let amp1 = self.state[j];

                self.state[i] = cos_half * amp0 - sin_half * amp1;
                self.state[j] = sin_half * amp0 + cos_half * amp1;
            }
        }

        Ok(())
    }

    /// Apply RZ gate
    fn apply_rz(&mut self, target: usize, angle: f64) -> Result<()> {
        if target >= self.num_qubits {
            return Err(SimulatorError::InvalidParameter(
                "Target qubit out of range".to_string(),
            ));
        }

        let exp_neg = Complex64::new(0.0, -angle / 2.0).exp();
        let exp_pos = Complex64::new(0.0, angle / 2.0).exp();

        for i in 0..(1 << self.num_qubits) {
            if (i >> target) & 1 == 0 {
                self.state[i] *= exp_neg;
            } else {
                self.state[i] *= exp_pos;
            }
        }

        Ok(())
    }

    /// Get current state vector
    #[must_use]
    pub const fn get_state(&self) -> &Array1<Complex64> {
        &self.state
    }

    /// Get simulator statistics
    #[must_use]
    pub const fn get_stats(&self) -> &JITSimulatorStats {
        &self.stats
    }

    /// Get compiler statistics
    #[must_use]
    pub fn get_compiler_stats(&self) -> JITCompilerStats {
        self.compiler.get_stats()
    }
}

/// JIT simulator statistics
#[derive(Debug, Clone)]
pub struct JITSimulatorStats {
    /// Number of compiled executions
    pub compiled_executions: usize,
    /// Number of interpreted executions
    pub interpreted_executions: usize,
    /// Total time spent in compiled execution
    pub total_compiled_time: Duration,
    /// Total time spent in interpreted execution
    pub total_interpreted_time: Duration,
    /// JIT compilation speedup factor
    pub speedup_factor: f64,
}

impl Default for JITSimulatorStats {
    fn default() -> Self {
        Self {
            compiled_executions: 0,
            interpreted_executions: 0,
            total_compiled_time: Duration::from_secs(0),
            total_interpreted_time: Duration::from_secs(0),
            speedup_factor: 1.0,
        }
    }
}

impl JITSimulatorStats {
    /// Update speedup factor
    pub fn update_speedup_factor(&mut self) {
        if self.compiled_executions > 0 && self.interpreted_executions > 0 {
            let avg_compiled =
                self.total_compiled_time.as_secs_f64() / self.compiled_executions as f64;
            let avg_interpreted =
                self.total_interpreted_time.as_secs_f64() / self.interpreted_executions as f64;

            if avg_compiled > 0.0 {
                self.speedup_factor = avg_interpreted / avg_compiled;
            }
        }
    }
}

/// Benchmark JIT compilation system
pub fn benchmark_jit_compilation() -> Result<JITBenchmarkResults> {
    let num_qubits = 4;
    let config = JITConfig::default();
    let mut simulator = JITQuantumSimulator::new(num_qubits, config);

    // Create test gate sequences
    let gate_sequences = create_test_gate_sequences(num_qubits);

    let mut results = JITBenchmarkResults {
        total_sequences: gate_sequences.len(),
        compiled_sequences: 0,
        interpreted_sequences: 0,
        average_compilation_time: Duration::from_secs(0),
        average_execution_time_compiled: Duration::from_secs(0),
        average_execution_time_interpreted: Duration::from_secs(0),
        speedup_factor: 1.0,
        compilation_success_rate: 0.0,
        memory_usage_reduction: 0.0,
    };

    let mut total_compilation_time = Duration::from_secs(0);
    let mut total_execution_time_compiled = Duration::from_secs(0);
    let mut total_execution_time_interpreted = Duration::from_secs(0);

    // Run benchmarks
    for sequence in &gate_sequences {
        // First run (interpreted)
        let interpreted_time = simulator.apply_gate_sequence(sequence)?;
        total_execution_time_interpreted += interpreted_time;
        results.interpreted_sequences += 1;

        // Second run (potentially compiled)
        let execution_time = simulator.apply_gate_sequence(sequence)?;

        // Check if it was compiled
        if simulator.get_stats().compiled_executions > results.compiled_sequences {
            total_execution_time_compiled += execution_time;
            results.compiled_sequences += 1;
        }
    }

    // Calculate averages
    if results.compiled_sequences > 0 {
        results.average_execution_time_compiled =
            total_execution_time_compiled / results.compiled_sequences as u32;
    }

    if results.interpreted_sequences > 0 {
        results.average_execution_time_interpreted =
            total_execution_time_interpreted / results.interpreted_sequences as u32;
    }

    // Calculate speedup factor
    if results.average_execution_time_compiled.as_secs_f64() > 0.0 {
        results.speedup_factor = results.average_execution_time_interpreted.as_secs_f64()
            / results.average_execution_time_compiled.as_secs_f64();
    }

    // Calculate compilation success rate
    results.compilation_success_rate =
        results.compiled_sequences as f64 / results.total_sequences as f64;

    // Get compiler stats
    let compiler_stats = simulator.get_compiler_stats();
    if compiler_stats.total_compilations > 0 {
        results.average_compilation_time =
            compiler_stats.total_compilation_time / compiler_stats.total_compilations as u32;
    }

    Ok(results)
}

/// Create test gate sequences for benchmarking
fn create_test_gate_sequences(num_qubits: usize) -> Vec<Vec<InterfaceGate>> {
    let mut sequences = Vec::new();

    // Simple sequences
    for target in 0..num_qubits {
        // Single Pauli-X gate
        sequences.push(vec![InterfaceGate::new(
            InterfaceGateType::PauliX,
            vec![target],
        )]);

        // Hadamard gate
        sequences.push(vec![InterfaceGate::new(
            InterfaceGateType::Hadamard,
            vec![target],
        )]);

        // Rotation gate
        sequences.push(vec![InterfaceGate::new(
            InterfaceGateType::RX(std::f64::consts::PI / 4.0),
            vec![target],
        )]);
    }

    // Two-qubit sequences
    for control in 0..num_qubits {
        for target in 0..num_qubits {
            if control != target {
                sequences.push(vec![InterfaceGate::new(
                    InterfaceGateType::CNOT,
                    vec![control, target],
                )]);
            }
        }
    }

    // Longer sequences for compilation testing
    for target in 0..num_qubits {
        let sequence = vec![
            InterfaceGate::new(InterfaceGateType::Hadamard, vec![target]),
            InterfaceGate::new(
                InterfaceGateType::RZ(std::f64::consts::PI / 8.0),
                vec![target],
            ),
            InterfaceGate::new(InterfaceGateType::Hadamard, vec![target]),
        ];
        sequences.push(sequence);
    }

    // Repeat sequences multiple times to trigger compilation
    let mut repeated_sequences = Vec::new();
    for sequence in &sequences[0..5] {
        // Take first 5 sequences
        for _ in 0..15 {
            // Repeat each 15 times
            repeated_sequences.push(sequence.clone());
        }
    }

    sequences.extend(repeated_sequences);
    sequences
}

/// JIT benchmark results
#[derive(Debug, Clone)]
pub struct JITBenchmarkResults {
    /// Total number of gate sequences tested
    pub total_sequences: usize,
    /// Number of sequences that were compiled
    pub compiled_sequences: usize,
    /// Number of sequences that were interpreted
    pub interpreted_sequences: usize,
    /// Average compilation time
    pub average_compilation_time: Duration,
    /// Average execution time for compiled sequences
    pub average_execution_time_compiled: Duration,
    /// Average execution time for interpreted sequences
    pub average_execution_time_interpreted: Duration,
    /// Speedup factor (interpreted / compiled)
    pub speedup_factor: f64,
    /// Compilation success rate
    pub compilation_success_rate: f64,
    /// Memory usage reduction
    pub memory_usage_reduction: f64,
}

impl fmt::Display for JITBenchmarkResults {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        writeln!(f, "JIT Compilation Benchmark Results:")?;
        writeln!(f, "  Total sequences: {}", self.total_sequences)?;
        writeln!(f, "  Compiled sequences: {}", self.compiled_sequences)?;
        writeln!(f, "  Interpreted sequences: {}", self.interpreted_sequences)?;
        writeln!(
            f,
            "  Average compilation time: {:?}",
            self.average_compilation_time
        )?;
        writeln!(
            f,
            "  Average execution time (compiled): {:?}",
            self.average_execution_time_compiled
        )?;
        writeln!(
            f,
            "  Average execution time (interpreted): {:?}",
            self.average_execution_time_interpreted
        )?;
        writeln!(f, "  Speedup factor: {:.2}x", self.speedup_factor)?;
        writeln!(
            f,
            "  Compilation success rate: {:.1}%",
            self.compilation_success_rate * 100.0
        )?;
        write!(
            f,
            "  Memory usage reduction: {:.1}%",
            self.memory_usage_reduction * 100.0
        )
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_jit_compiler_creation() {
        let config = JITConfig::default();
        let compiler = JITCompiler::new(config);
        let stats = compiler.get_stats();
        assert_eq!(stats.total_compilations, 0);
    }

    #[test]
    fn test_pattern_extraction() {
        let config = JITConfig::default();
        let _compiler = JITCompiler::new(config);

        let gates = vec![
            InterfaceGate::new(InterfaceGateType::Hadamard, vec![0]),
            InterfaceGate::new(InterfaceGateType::PauliX, vec![1]),
        ];

        let pattern =
            JITCompiler::extract_pattern(&gates).expect("Pattern extraction should succeed");
        assert_eq!(pattern.gate_types.len(), 2);
        assert_eq!(pattern.frequency, 1);
    }

    #[test]
    fn test_gate_matrix_generation() {
        let config = JITConfig::default();
        let _compiler = JITCompiler::new(config);

        let pauli_x = JITCompiler::get_gate_matrix(&InterfaceGateType::PauliX)
            .expect("PauliX matrix generation should succeed");
        assert_eq!(pauli_x.shape(), [2, 2]);
        assert_eq!(pauli_x[(0, 1)], Complex64::new(1.0, 0.0));
        assert_eq!(pauli_x[(1, 0)], Complex64::new(1.0, 0.0));
    }

    #[test]
    fn test_pattern_analysis() {
        let mut analyzer = PatternAnalyzer::new();

        let gates = vec![
            InterfaceGate::new(InterfaceGateType::Hadamard, vec![0]),
            InterfaceGate::new(InterfaceGateType::Hadamard, vec![0]),
        ];

        let result = analyzer.analyze_pattern(&gates);
        assert_eq!(result.frequency, 1);
        assert!(result
            .optimization_suggestions
            .contains(&OptimizationSuggestion::GateFusion));
    }

    #[test]
    fn test_complexity_analysis() {
        let analyzer = ComplexityAnalyzer::new();

        let gates = vec![
            InterfaceGate::new(InterfaceGateType::PauliX, vec![0]),
            InterfaceGate::new(InterfaceGateType::CNOT, vec![0, 1]),
        ];

        let complexity = analyzer.analyze_complexity(&gates);
        assert_eq!(complexity.gate_count, 2);
        assert!(complexity.computational_cost > 0.0);
    }

    #[test]
    fn test_jit_simulator_creation() {
        let config = JITConfig::default();
        let simulator = JITQuantumSimulator::new(2, config);

        assert_eq!(simulator.num_qubits, 2);
        assert_eq!(simulator.state.len(), 4);
        assert_eq!(simulator.state[0], Complex64::new(1.0, 0.0));
    }

    #[test]
    fn test_gate_application() {
        let config = JITConfig::default();
        let mut simulator = JITQuantumSimulator::new(1, config);

        let gate = InterfaceGate::new(InterfaceGateType::PauliX, vec![0]);

        simulator
            .apply_gate_interpreted(&gate)
            .expect("PauliX gate application should succeed");

        // After Pauli-X, state should be |1⟩
        assert_eq!(simulator.state[0], Complex64::new(0.0, 0.0));
        assert_eq!(simulator.state[1], Complex64::new(1.0, 0.0));
    }

    #[test]
    fn test_hadamard_gate() {
        let config = JITConfig::default();
        let mut simulator = JITQuantumSimulator::new(1, config);

        let gate = InterfaceGate::new(InterfaceGateType::Hadamard, vec![0]);

        simulator
            .apply_gate_interpreted(&gate)
            .expect("Hadamard gate application should succeed");

        // After Hadamard, state should be (|0⟩ + |1⟩)/√2
        let sqrt2_inv = 1.0 / (2.0_f64).sqrt();
        assert!((simulator.state[0].re - sqrt2_inv).abs() < 1e-10);
        assert!((simulator.state[1].re - sqrt2_inv).abs() < 1e-10);
    }

    #[test]
    fn test_cnot_gate() {
        let config = JITConfig::default();
        let mut simulator = JITQuantumSimulator::new(2, config);

        // Prepare |10⟩ state
        simulator.state[0] = Complex64::new(0.0, 0.0);
        simulator.state[1] = Complex64::new(0.0, 0.0);
        simulator.state[2] = Complex64::new(1.0, 0.0);
        simulator.state[3] = Complex64::new(0.0, 0.0);

        let gate = InterfaceGate::new(InterfaceGateType::CNOT, vec![1, 0]);

        simulator
            .apply_gate_interpreted(&gate)
            .expect("CNOT gate application should succeed");

        // After CNOT, |10⟩ → |11⟩
        assert_eq!(simulator.state[0], Complex64::new(0.0, 0.0));
        assert_eq!(simulator.state[1], Complex64::new(0.0, 0.0));
        assert_eq!(simulator.state[2], Complex64::new(0.0, 0.0));
        assert_eq!(simulator.state[3], Complex64::new(1.0, 0.0));
    }

    #[test]
    fn test_rotation_gates() {
        let config = JITConfig::default();
        let mut simulator = JITQuantumSimulator::new(1, config);

        // Test RX gate
        let gate_rx = InterfaceGate::new(InterfaceGateType::RX(std::f64::consts::PI), vec![0]);

        simulator
            .apply_gate_interpreted(&gate_rx)
            .expect("RX gate application should succeed");

        // RX(π) should be equivalent to Pauli-X up to global phase
        // RX(π)|0⟩ = -i|1⟩, so we check the magnitude
        assert!((simulator.state[0].norm() - 0.0).abs() < 1e-10);
        assert!((simulator.state[1].norm() - 1.0).abs() < 1e-10);
    }

    #[test]
    fn test_gate_sequence_compilation() {
        let mut config = JITConfig::default();
        config.compilation_threshold = 1; // Compile after 1 usage

        let mut simulator = JITQuantumSimulator::new(2, config);

        let sequence = vec![
            InterfaceGate::new(InterfaceGateType::Hadamard, vec![0]),
            InterfaceGate::new(InterfaceGateType::PauliX, vec![1]),
        ];

        // First execution should be interpreted
        let _time1 = simulator
            .apply_gate_sequence(&sequence)
            .expect("First gate sequence should succeed");
        assert_eq!(simulator.get_stats().interpreted_executions, 1);

        // Second execution might be compiled
        let _time2 = simulator
            .apply_gate_sequence(&sequence)
            .expect("Second gate sequence should succeed");
        // Check compilation occurred
        assert!(simulator.get_compiler_stats().patterns_analyzed > 0);
    }

    #[test]
    fn test_optimization_suggestions() {
        let mut analyzer = PatternAnalyzer::new();

        // Sequence with fusion potential
        let gates = vec![
            InterfaceGate::new(InterfaceGateType::RX(std::f64::consts::PI / 4.0), vec![0]),
            InterfaceGate::new(InterfaceGateType::RY(std::f64::consts::PI / 2.0), vec![0]),
        ];

        let result = analyzer.analyze_pattern(&gates);
        assert!(result
            .optimization_suggestions
            .contains(&OptimizationSuggestion::GateFusion));
    }

    #[test]
    fn test_runtime_profiler() {
        let mut profiler = RuntimeProfiler::new();

        profiler.record_execution_time(Duration::from_millis(100));
        profiler.record_execution_time(Duration::from_millis(200));
        profiler.record_memory_usage(1024);
        profiler.record_memory_usage(2048);

        let stats = profiler.get_stats();
        assert_eq!(stats.sample_count, 2);
        assert_eq!(stats.average_memory_usage, 1536);
        assert_eq!(stats.peak_memory_usage, 2048);
    }

    #[test]
    fn test_constant_folding_optimization() {
        let config = JITConfig::default();
        let _compiler = JITCompiler::new(config);

        let mut instructions = vec![
            BytecodeInstruction::ApplySingleQubit {
                gate_type: InterfaceGateType::RX(0.0), // Zero rotation
                target: 0,
            },
            BytecodeInstruction::ApplySingleQubit {
                gate_type: InterfaceGateType::RY(std::f64::consts::PI),
                target: 0,
            },
        ];

        JITCompiler::apply_constant_folding(&mut instructions)
            .expect("Constant folding should succeed");

        // Check that zero rotation was folded to identity
        if let BytecodeInstruction::ApplySingleQubit { gate_type, .. } = &instructions[0] {
            assert_eq!(*gate_type, InterfaceGateType::Identity);
        }
    }

    #[test]
    fn test_dead_code_elimination() {
        let config = JITConfig::default();
        let _compiler = JITCompiler::new(config);

        let mut instructions = vec![
            BytecodeInstruction::ApplySingleQubit {
                gate_type: InterfaceGateType::Identity, // Identity operation
                target: 0,
            },
            BytecodeInstruction::ApplySingleQubit {
                gate_type: InterfaceGateType::RY(std::f64::consts::PI),
                target: 0,
            },
        ];

        let original_len = instructions.len();
        JITCompiler::apply_dead_code_elimination(&mut instructions)
            .expect("Dead code elimination should succeed");

        // Dead code should be eliminated
        assert!(instructions.len() <= original_len);
    }

    #[test]
    fn test_benchmark_jit_compilation() {
        let results =
            benchmark_jit_compilation().expect("JIT benchmark should complete successfully");

        assert!(results.total_sequences > 0);
        assert!(results.compilation_success_rate >= 0.0);
        assert!(results.compilation_success_rate <= 1.0);
        assert!(results.speedup_factor >= 0.0);
    }
}