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//! Metal-accelerated linear algebra operations for macOS
//!
//! This module provides GPU-accelerated linear algebra using Metal Performance Shaders (MPS)
//! and Accelerate framework integration.
//!
//! **Status:** scaffolding only — not yet implemented. Entry points honestly
//! error or report unavailability via SciRS2 platform detection rather than
//! fabricating results. A future implementation would use:
//! - Metal Performance Shaders (MPS) for matrix operations
//! - Accelerate.framework for optimized BLAS/LAPACK on Apple Silicon
//! - Custom Metal compute shaders for quantum-specific operations
use crate::error::{Result, SimulatorError};
use scirs2_core::ndarray::{Array2, ArrayView2};
use scirs2_core::Complex64;
use std::sync::Arc;
/// Metal-accelerated linear algebra backend for macOS
pub struct MetalLinalgBackend {
/// Metal device handle (placeholder)
_device: Arc<()>,
/// Enable performance profiling
pub enable_profiling: bool,
}
impl MetalLinalgBackend {
/// Create a new Metal linear algebra backend.
///
/// The Metal/Accelerate backend is not yet implemented, so this honestly
/// errors instead of returning a non-functional backend.
pub fn new() -> Result<Self> {
Err(SimulatorError::GpuError(
"Metal linear algebra not yet implemented. Please use CPU linear algebra on macOS."
.to_string(),
))
}
/// Create an instance optimized for quantum machine learning.
///
/// Not yet implemented; honestly errors rather than returning a stub backend.
pub fn new_qml_optimized() -> Result<Self> {
Err(SimulatorError::GpuError(
"Metal QML optimization not yet implemented".to_string(),
))
}
/// Matrix multiplication using Metal Performance Shaders
pub fn matmul(
&self,
_a: &ArrayView2<Complex64>,
_b: &ArrayView2<Complex64>,
) -> Result<Array2<Complex64>> {
// A real backend would dispatch MPSMatrixMultiplication here.
Err(SimulatorError::GpuError(
"Metal matrix multiplication not yet implemented".to_string(),
))
}
/// Eigenvalue decomposition using Accelerate framework
pub fn eig(
&self,
_matrix: &ArrayView2<Complex64>,
) -> Result<(Array2<Complex64>, Array2<Complex64>)> {
// A real backend would call Accelerate's LAPACK eigen routines here.
Err(SimulatorError::GpuError(
"Metal eigenvalue decomposition not yet implemented".to_string(),
))
}
/// Singular value decomposition
pub fn svd(
&self,
_matrix: &ArrayView2<Complex64>,
) -> Result<(Array2<Complex64>, Array2<f64>, Array2<Complex64>)> {
// A real backend would call Accelerate's LAPACK SVD (or MPS) here.
Err(SimulatorError::GpuError(
"Metal SVD not yet implemented".to_string(),
))
}
/// Check if Metal Performance Shaders is available.
///
/// Delegates to SciRS2's platform detection (`metal_available`), true only on
/// macOS with the Metal backend compiled in. The QuantRS2 MPS compute path is
/// still unimplemented, so the compute methods error even when this is `true`.
pub fn is_mps_available() -> bool {
scirs2_core::simd_ops::PlatformCapabilities::detect().metal_available
}
/// Get Metal device capabilities.
///
/// Reports the platform's Metal availability honestly via SciRS2; detailed
/// device introspection awaits a real Metal backend implementation.
pub fn get_device_info() -> String {
if scirs2_core::simd_ops::PlatformCapabilities::detect().metal_available {
"Metal-capable platform detected; QuantRS2 Metal backend not yet implemented"
.to_string()
} else {
"Metal not available on this platform".to_string()
}
}
}
// Future implementation notes:
//
// 1. Metal Shaders for Quantum Gates:
// - Implement custom compute shaders for Pauli gates
// - Optimize for sparse operations
// - Use threadgroup memory for local computations
//
// 2. Memory Management:
// - Leverage unified memory on Apple Silicon
// - Implement efficient buffer management
// - Use shared memory between CPU and GPU
//
// 3. Performance Optimizations:
// - Tile-based rendering for large state vectors
// - Parallel command encoding
// - Async compute with multiple command queues
//
// 4. Integration with Accelerate:
// - Use vDSP for signal processing
// - Use BLAS for basic operations
// - Use LAPACK for advanced decompositions