ronn-providers 0.1.0

//! Multi-GPU memory management and synchronization system.
//!
//! This module provides advanced memory management capabilities for multi-GPU setups,
//! including P2P transfers, memory synchronization, and unified memory pools.

use std::collections::HashMap;
use std::sync::{Arc, Mutex, RwLock};

use anyhow::{Result, anyhow};
use candle_core::{Device, Tensor as CandleTensor};
use ronn_core::{DataType, MemoryType, TensorBuffer};
use tracing::{debug, info, warn};

/// Multi-GPU memory manager coordinating memory across devices.
#[derive(Debug)]
pub struct MultiGpuMemoryManager {
    /// Memory pools for each device.
    device_pools: HashMap<usize, Arc<Mutex<DeviceMemoryPool>>>,
    /// P2P connectivity matrix between devices.
    p2p_matrix: Arc<RwLock<P2PConnectivityMatrix>>,
    /// Global memory allocation tracking.
    global_stats: Arc<Mutex<GlobalMemoryStats>>,
    /// Memory synchronization manager.
    sync_manager: Arc<SyncManager>,
    /// Configuration for memory management.
    config: MultiGpuMemoryConfig,
}

/// Configuration for multi-GPU memory management.
#[derive(Debug, Clone)]
pub struct MultiGpuMemoryConfig {
    /// Enable P2P memory transfers between GPUs.
    pub enable_p2p: bool,
    /// Memory pool size per device in bytes.
    pub pool_size_per_device: usize,
    /// Enable unified memory addressing across devices.
    pub enable_unified_memory: bool,
    /// Memory synchronization strategy.
    pub sync_strategy: SyncStrategy,
    /// Maximum P2P transfer size in bytes.
    pub max_p2p_transfer_size: usize,
    /// Enable memory compression for transfers.
    pub enable_compression: bool,
}

impl Default for MultiGpuMemoryConfig {
    fn default() -> Self {
        Self {
            enable_p2p: true,
            pool_size_per_device: 2 * 1024 * 1024 * 1024, // 2GB per device
            enable_unified_memory: true,
            sync_strategy: SyncStrategy::Explicit,
            max_p2p_transfer_size: 256 * 1024 * 1024, // 256MB
            enable_compression: false,
        }
    }
}

/// Memory synchronization strategies.
#[derive(Debug, Clone, Copy)]
pub enum SyncStrategy {
    /// Explicit synchronization - manual sync points.
    Explicit,
    /// Automatic synchronization after each operation.
    Automatic,
    /// Stream-based synchronization using events.
    StreamBased,
}

/// Per-device memory pool for efficient allocation.
#[derive(Debug)]
pub struct DeviceMemoryPool {
    /// Device ID for this pool.
    device_id: usize,
    /// Available memory blocks.
    available_blocks: Vec<MemoryBlock>,
    /// Currently allocated blocks.
    allocated_blocks: HashMap<usize, MemoryBlock>,
    /// Pool statistics.
    stats: MemoryPoolStats,
    /// Next allocation ID.
    next_alloc_id: usize,
}

/// A memory block within a device pool.
#[derive(Debug, Clone)]
pub struct MemoryBlock {
    /// Unique allocation ID.
    alloc_id: usize,
    /// Device ID where this block resides.
    device_id: usize,
    /// Size of the memory block in bytes.
    size: usize,
    /// Memory alignment requirements.
    alignment: usize,
    /// Virtual address (placeholder for actual GPU pointer).
    virtual_address: usize,
    /// Whether this block supports P2P access.
    p2p_accessible: bool,
    /// Data type stored in this block.
    data_type: DataType,
    /// Reference count for shared access.
    ref_count: usize,
}

/// Statistics for a device memory pool.
#[derive(Debug, Default, Clone)]
pub struct MemoryPoolStats {
    /// Total pool size in bytes.
    pub total_size: usize,
    /// Currently allocated bytes.
    pub allocated_bytes: usize,
    /// Available bytes.
    pub available_bytes: usize,
    /// Number of active allocations.
    pub active_allocations: usize,
    /// Peak memory usage.
    pub peak_usage: usize,
    /// Number of P2P transfers initiated from this device.
    pub p2p_transfers_out: u64,
    /// Number of P2P transfers received by this device.
    pub p2p_transfers_in: u64,
    /// Total bytes transferred via P2P.
    pub total_p2p_bytes: u64,
}

/// P2P connectivity information between GPU devices.
#[derive(Debug)]
pub struct P2PConnectivityMatrix {
    /// Matrix indicating P2P support between devices [from][to].
    connectivity: HashMap<(usize, usize), P2PCapability>,
    /// Bandwidth measurements between device pairs.
    bandwidth_matrix: HashMap<(usize, usize), f64>,
    /// Latency measurements between device pairs.
    latency_matrix: HashMap<(usize, usize), f64>,
}

/// P2P capability information between two devices.
#[derive(Debug, Clone, Copy)]
pub struct P2PCapability {
    /// Whether P2P access is supported.
    pub supported: bool,
    /// P2P access bandwidth in GB/s.
    pub bandwidth_gbps: f64,
    /// P2P access latency in microseconds.
    pub latency_us: f64,
    /// Whether the connection is NVLink or PCIe.
    pub is_nvlink: bool,
}

/// Global memory statistics across all devices.
#[derive(Debug, Default, Clone)]
pub struct GlobalMemoryStats {
    /// Total memory across all devices.
    pub total_memory: usize,
    /// Total allocated memory across all devices.
    pub allocated_memory: usize,
    /// Memory fragmentation percentage.
    pub fragmentation_percent: f32,
    /// Number of cross-device transfers.
    pub cross_device_transfers: u64,
    /// Total bytes transferred between devices.
    pub total_transfer_bytes: u64,
    /// Average transfer bandwidth.
    pub avg_transfer_bandwidth_gbps: f64,
}

/// Memory synchronization manager for coordinating operations.
#[derive(Debug)]
pub struct SyncManager {
    /// Active synchronization events per device.
    sync_events: Arc<Mutex<HashMap<usize, Vec<SyncEvent>>>>,
    /// Stream dependencies between devices.
    stream_deps: Arc<Mutex<HashMap<usize, Vec<usize>>>>,
    /// Synchronization strategy.
    strategy: SyncStrategy,
}

/// Synchronization event for memory operations.
#[derive(Debug, Clone)]
pub struct SyncEvent {
    /// Unique event ID.
    pub event_id: usize,
    /// Device where the event was recorded.
    pub device_id: usize,
    /// Type of synchronization event.
    pub event_type: SyncEventType,
    /// Timestamp when event was created.
    pub timestamp: std::time::Instant,
    /// Whether the event has been completed.
    pub completed: bool,
}

/// Types of synchronization events.
#[derive(Debug, Clone, Copy)]
pub enum SyncEventType {
    /// Memory allocation event.
    Allocation,
    /// Memory transfer initiation.
    TransferStart,
    /// Memory transfer completion.
    TransferComplete,
    /// Kernel execution start.
    KernelStart,
    /// Kernel execution completion.
    KernelComplete,
    /// Device synchronization.
    DeviceSync,
}

impl MultiGpuMemoryManager {
    /// Create a new multi-GPU memory manager.
    pub fn new(device_ids: Vec<usize>, config: MultiGpuMemoryConfig) -> Result<Self> {
        let mut device_pools = HashMap::new();

        // Initialize memory pools for each device
        for &device_id in &device_ids {
            let pool = DeviceMemoryPool::new(device_id, config.pool_size_per_device);
            device_pools.insert(device_id, Arc::new(Mutex::new(pool)));
            info!("Initialized memory pool for device {}", device_id);
        }

        // Initialize P2P connectivity matrix
        let p2p_matrix = Arc::new(RwLock::new(P2PConnectivityMatrix::discover_connectivity(
            &device_ids,
        )?));

        // Initialize synchronization manager
        let sync_manager = Arc::new(SyncManager::new(config.sync_strategy));

        let global_stats = Arc::new(Mutex::new(GlobalMemoryStats::default()));

        info!(
            "Created multi-GPU memory manager for {} devices",
            device_ids.len()
        );

        Ok(Self {
            device_pools,
            p2p_matrix,
            global_stats,
            sync_manager,
            config,
        })
    }

    /// Allocate memory on a specific device.
    pub fn allocate_on_device(
        &self,
        device_id: usize,
        size: usize,
        alignment: usize,
        data_type: DataType,
    ) -> Result<MemoryBlock> {
        let pool = self
            .device_pools
            .get(&device_id)
            .ok_or_else(|| anyhow!("Device {} not found", device_id))?;

        let mut pool = pool.lock().unwrap();
        let block = pool.allocate(size, alignment, data_type)?;

        // Update global statistics
        self.update_global_stats();

        // Create synchronization event
        if matches!(
            self.config.sync_strategy,
            SyncStrategy::Automatic | SyncStrategy::StreamBased
        ) {
            let event = SyncEvent {
                event_id: self.generate_event_id(),
                device_id,
                event_type: SyncEventType::Allocation,
                timestamp: std::time::Instant::now(),
                completed: true,
            };
            self.sync_manager.record_event(event);
        }

        debug!("Allocated {} bytes on device {}", size, device_id);
        Ok(block)
    }

    /// Deallocate memory block.
    pub fn deallocate(&self, block: MemoryBlock) -> Result<()> {
        let pool = self
            .device_pools
            .get(&block.device_id)
            .ok_or_else(|| anyhow!("Device {} not found", block.device_id))?;

        let mut pool = pool.lock().unwrap();
        pool.deallocate(block)?;

        self.update_global_stats();
        Ok(())
    }

    /// Transfer data between devices using P2P if available.
    pub fn transfer_between_devices(
        &self,
        src_block: &MemoryBlock,
        dst_device_id: usize,
        size: usize,
    ) -> Result<MemoryBlock> {
        let src_device_id = src_block.device_id;

        // Check if P2P is available
        let p2p_matrix = self.p2p_matrix.read().unwrap();
        let p2p_capability = p2p_matrix.get_capability(src_device_id, dst_device_id);

        if self.config.enable_p2p && p2p_capability.supported {
            self.transfer_p2p(src_block, dst_device_id, size)
        } else {
            self.transfer_via_host(src_block, dst_device_id, size)
        }
    }

    /// Synchronize operations across all devices.
    pub fn synchronize_all(&self) -> Result<()> {
        debug!("Synchronizing all devices");

        match self.config.sync_strategy {
            SyncStrategy::Explicit => {
                // Wait for all pending operations to complete
                for &device_id in self.device_pools.keys() {
                    self.synchronize_device(device_id)?;
                }
            }
            SyncStrategy::Automatic => {
                // Already synchronized automatically
            }
            SyncStrategy::StreamBased => {
                // Synchronize using events
                self.sync_manager.synchronize_streams()?;
            }
        }

        info!("All devices synchronized");
        Ok(())
    }

    /// Get memory statistics for all devices.
    pub fn get_memory_stats(&self) -> HashMap<usize, MemoryPoolStats> {
        let mut stats = HashMap::new();

        for (&device_id, pool) in &self.device_pools {
            let pool = pool.lock().unwrap();
            stats.insert(device_id, pool.stats.clone());
        }

        stats
    }

    /// Get global memory statistics.
    pub fn get_global_stats(&self) -> GlobalMemoryStats {
        let stats = self.global_stats.lock().unwrap();
        (*stats).clone()
    }

    /// Get P2P connectivity information.
    pub fn get_p2p_info(&self) -> HashMap<(usize, usize), P2PCapability> {
        let matrix = self.p2p_matrix.read().unwrap();
        matrix.connectivity.clone()
    }

    /// Optimize memory layout across devices for a given access pattern.
    pub fn optimize_memory_layout(&self, access_pattern: &AccessPattern) -> Result<MemoryLayout> {
        // Analyze access pattern and determine optimal placement
        let mut layout = MemoryLayout::new();

        for allocation in &access_pattern.allocations {
            let optimal_device = self.select_optimal_device(allocation)?;
            layout.assignments.insert(allocation.id, optimal_device);
        }

        Ok(layout)
    }

    // Private helper methods

    fn transfer_p2p(
        &self,
        src_block: &MemoryBlock,
        dst_device_id: usize,
        size: usize,
    ) -> Result<MemoryBlock> {
        debug!(
            "P2P transfer from device {} to device {}",
            src_block.device_id, dst_device_id
        );

        // Record transfer start event
        let start_event = SyncEvent {
            event_id: self.generate_event_id(),
            device_id: src_block.device_id,
            event_type: SyncEventType::TransferStart,
            timestamp: std::time::Instant::now(),
            completed: false,
        };
        self.sync_manager.record_event(start_event.clone());

        // Allocate destination memory
        let dst_block = self.allocate_on_device(
            dst_device_id,
            size,
            src_block.alignment,
            src_block.data_type,
        )?;

        // Simulate P2P transfer (in real implementation, would use CUDA P2P APIs)
        let transfer_time = self.simulate_p2p_transfer(src_block.device_id, dst_device_id, size)?;
        std::thread::sleep(transfer_time);

        // Record transfer completion
        let complete_event = SyncEvent {
            event_id: start_event.event_id,
            device_id: dst_device_id,
            event_type: SyncEventType::TransferComplete,
            timestamp: std::time::Instant::now(),
            completed: true,
        };
        self.sync_manager.record_event(complete_event);

        // Update P2P statistics
        self.update_p2p_stats(src_block.device_id, dst_device_id, size);

        Ok(dst_block)
    }

    fn transfer_via_host(
        &self,
        src_block: &MemoryBlock,
        dst_device_id: usize,
        size: usize,
    ) -> Result<MemoryBlock> {
        debug!(
            "Host transfer from device {} to device {}",
            src_block.device_id, dst_device_id
        );

        // Simulate slower host-based transfer
        let transfer_time = std::time::Duration::from_micros(size as u64 / 1000); // ~1GB/s
        std::thread::sleep(transfer_time);

        let dst_block = self.allocate_on_device(
            dst_device_id,
            size,
            src_block.alignment,
            src_block.data_type,
        )?;

        Ok(dst_block)
    }

    fn synchronize_device(&self, device_id: usize) -> Result<()> {
        debug!("Synchronizing device {}", device_id);

        // In real implementation, would call cudaDeviceSynchronize() or similar
        std::thread::sleep(std::time::Duration::from_micros(10));

        Ok(())
    }

    fn simulate_p2p_transfer(
        &self,
        src_device: usize,
        dst_device: usize,
        size: usize,
    ) -> Result<std::time::Duration> {
        let p2p_matrix = self.p2p_matrix.read().unwrap();
        let capability = p2p_matrix.get_capability(src_device, dst_device);

        let bandwidth_bps = capability.bandwidth_gbps * 1_000_000_000.0;
        let transfer_time_s = size as f64 / bandwidth_bps;
        let latency_s = capability.latency_us / 1_000_000.0;

        let total_time_s = transfer_time_s + latency_s;
        Ok(std::time::Duration::from_secs_f64(total_time_s))
    }

    fn update_global_stats(&self) {
        let mut global = self.global_stats.lock().unwrap();

        global.total_memory = 0;
        global.allocated_memory = 0;

        for pool in self.device_pools.values() {
            let pool_stats = &pool.lock().unwrap().stats;
            global.total_memory += pool_stats.total_size;
            global.allocated_memory += pool_stats.allocated_bytes;
            global.cross_device_transfers += pool_stats.p2p_transfers_out;
            global.total_transfer_bytes += pool_stats.total_p2p_bytes;
        }

        if global.total_memory > 0 {
            let used_percent = global.allocated_memory as f32 / global.total_memory as f32;
            global.fragmentation_percent = (used_percent * 100.0).min(100.0);
        }
    }

    fn update_p2p_stats(&self, src_device: usize, dst_device: usize, bytes: usize) {
        if let Some(src_pool) = self.device_pools.get(&src_device) {
            let mut pool = src_pool.lock().unwrap();
            pool.stats.p2p_transfers_out += 1;
            pool.stats.total_p2p_bytes += bytes as u64;
        }

        if let Some(dst_pool) = self.device_pools.get(&dst_device) {
            let mut pool = dst_pool.lock().unwrap();
            pool.stats.p2p_transfers_in += 1;
        }
    }

    fn generate_event_id(&self) -> usize {
        static COUNTER: std::sync::atomic::AtomicUsize = std::sync::atomic::AtomicUsize::new(0);
        COUNTER.fetch_add(1, std::sync::atomic::Ordering::SeqCst)
    }

    fn select_optimal_device(&self, allocation: &AllocationRequest) -> Result<usize> {
        // Simple heuristic: select device with most available memory
        let mut best_device = allocation.preferred_devices.get(0).copied().unwrap_or(0);
        let mut best_available = 0;

        for &device_id in &allocation.preferred_devices {
            if let Some(pool) = self.device_pools.get(&device_id) {
                let pool = pool.lock().unwrap();
                if pool.stats.available_bytes > best_available {
                    best_available = pool.stats.available_bytes;
                    best_device = device_id;
                }
            }
        }

        Ok(best_device)
    }
}

impl DeviceMemoryPool {
    fn new(device_id: usize, total_size: usize) -> Self {
        Self {
            device_id,
            available_blocks: vec![],
            allocated_blocks: HashMap::new(),
            stats: MemoryPoolStats {
                total_size,
                allocated_bytes: 0,
                available_bytes: total_size,
                active_allocations: 0,
                peak_usage: 0,
                p2p_transfers_out: 0,
                p2p_transfers_in: 0,
                total_p2p_bytes: 0,
            },
            next_alloc_id: 1,
        }
    }

    fn allocate(
        &mut self,
        size: usize,
        alignment: usize,
        data_type: DataType,
    ) -> Result<MemoryBlock> {
        if size > self.stats.available_bytes {
            return Err(anyhow!(
                "Insufficient memory on device {}: requested {}, available {}",
                self.device_id,
                size,
                self.stats.available_bytes
            ));
        }

        let alloc_id = self.next_alloc_id;
        self.next_alloc_id += 1;

        let block = MemoryBlock {
            alloc_id,
            device_id: self.device_id,
            size,
            alignment,
            virtual_address: alloc_id * 0x1000, // Simulated address
            p2p_accessible: true,               // Assume P2P capable
            data_type,
            ref_count: 1,
        };

        self.allocated_blocks.insert(alloc_id, block.clone());
        self.stats.allocated_bytes += size;
        self.stats.available_bytes -= size;
        self.stats.active_allocations += 1;
        self.stats.peak_usage = self.stats.peak_usage.max(self.stats.allocated_bytes);

        Ok(block)
    }

    fn deallocate(&mut self, block: MemoryBlock) -> Result<()> {
        if let Some(stored_block) = self.allocated_blocks.remove(&block.alloc_id) {
            self.stats.allocated_bytes -= stored_block.size;
            self.stats.available_bytes += stored_block.size;
            self.stats.active_allocations -= 1;
            Ok(())
        } else {
            Err(anyhow!("Block not found for deallocation"))
        }
    }
}

impl P2PConnectivityMatrix {
    fn discover_connectivity(device_ids: &[usize]) -> Result<Self> {
        let mut connectivity = HashMap::new();
        let mut bandwidth_matrix = HashMap::new();
        let mut latency_matrix = HashMap::new();

        // Simulate P2P discovery (in real implementation, would query CUDA)
        for &src in device_ids {
            for &dst in device_ids {
                if src != dst {
                    // Simulate P2P capability based on device proximity
                    let is_nvlink = (src.abs_diff(dst)) == 1; // Adjacent devices have NVLink
                    let capability = P2PCapability {
                        supported: true,
                        bandwidth_gbps: if is_nvlink { 300.0 } else { 16.0 }, // NVLink vs PCIe
                        latency_us: if is_nvlink { 1.0 } else { 5.0 },
                        is_nvlink,
                    };

                    connectivity.insert((src, dst), capability);
                    bandwidth_matrix.insert((src, dst), capability.bandwidth_gbps);
                    latency_matrix.insert((src, dst), capability.latency_us);
                }
            }
        }

        Ok(Self {
            connectivity,
            bandwidth_matrix,
            latency_matrix,
        })
    }

    fn get_capability(&self, src: usize, dst: usize) -> P2PCapability {
        self.connectivity
            .get(&(src, dst))
            .copied()
            .unwrap_or(P2PCapability {
                supported: false,
                bandwidth_gbps: 0.0,
                latency_us: f64::INFINITY,
                is_nvlink: false,
            })
    }
}

impl SyncManager {
    fn new(strategy: SyncStrategy) -> Self {
        Self {
            sync_events: Arc::new(Mutex::new(HashMap::new())),
            stream_deps: Arc::new(Mutex::new(HashMap::new())),
            strategy,
        }
    }

    fn record_event(&self, event: SyncEvent) {
        let mut events = self.sync_events.lock().unwrap();
        events.entry(event.device_id).or_default().push(event);
    }

    fn synchronize_streams(&self) -> Result<()> {
        debug!("Synchronizing streams using events");

        // Wait for all recorded events to complete
        let events = self.sync_events.lock().unwrap();
        for device_events in events.values() {
            for event in device_events {
                if !event.completed {
                    // In real implementation, would wait for CUDA event
                    std::thread::sleep(std::time::Duration::from_micros(1));
                }
            }
        }

        Ok(())
    }
}

/// Memory access pattern analysis for optimization.
#[derive(Debug)]
pub struct AccessPattern {
    /// Memory allocation requests.
    pub allocations: Vec<AllocationRequest>,
    /// Data transfer patterns between devices.
    pub transfer_patterns: Vec<TransferPattern>,
}

/// Request for memory allocation with preferences.
#[derive(Debug)]
pub struct AllocationRequest {
    /// Unique allocation ID.
    pub id: usize,
    /// Size of allocation in bytes.
    pub size: usize,
    /// Data type for this allocation.
    pub data_type: DataType,
    /// Preferred devices for this allocation.
    pub preferred_devices: Vec<usize>,
    /// How frequently this allocation is accessed.
    pub access_frequency: f32,
}

/// Pattern of data transfers between devices.
#[derive(Debug)]
pub struct TransferPattern {
    /// Source allocation ID.
    pub src_allocation: usize,
    /// Destination device ID.
    pub dst_device: usize,
    /// Transfer frequency.
    pub frequency: f32,
    /// Transfer size in bytes.
    pub size: usize,
}

/// Optimized memory layout assignment.
#[derive(Debug)]
pub struct MemoryLayout {
    /// Mapping of allocation ID to device ID.
    pub assignments: HashMap<usize, usize>, // allocation_id -> device_id
}

impl MemoryLayout {
    fn new() -> Self {
        Self {
            assignments: HashMap::new(),
        }
    }
}