quantrs2-sim 0.1.3

//! CUDA stream management for asynchronous GPU operations.
//!
//! This module provides CUDA stream creation, synchronization,
//! and management for parallel GPU kernel execution.

#[cfg(feature = "advanced_math")]
use std::sync::{Arc, Mutex};

#[cfg(feature = "advanced_math")]
use crate::error::Result;

#[cfg(feature = "advanced_math")]
use super::context::CudaEvent;

// Placeholder types for actual CUDA handles
#[cfg(feature = "advanced_math")]
pub type CudaStreamHandle = usize;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum StreamPriority {
    Low,
    Normal,
    High,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum StreamFlags {
    Default,
    NonBlocking,
}

#[cfg(feature = "advanced_math")]
pub struct CudaStream {
    id: usize,
    handle: Arc<Mutex<Option<CudaStreamHandle>>>,
    priority: StreamPriority,
    flags: StreamFlags,
}

#[cfg(feature = "advanced_math")]
impl CudaStream {
    pub fn new() -> Result<Self> {
        Self::with_priority_and_flags(StreamPriority::Normal, StreamFlags::Default)
    }

    pub fn with_priority_and_flags(priority: StreamPriority, flags: StreamFlags) -> Result<Self> {
        let id = Self::allocate_stream_id();
        let handle = Arc::new(Mutex::new(Self::create_cuda_stream(priority, flags)?));

        Ok(Self {
            id,
            handle,
            priority,
            flags,
        })
    }

    pub fn get_id(&self) -> usize {
        self.id
    }

    pub fn get_priority(&self) -> StreamPriority {
        self.priority
    }

    pub fn get_flags(&self) -> StreamFlags {
        self.flags
    }

    pub fn synchronize(&self) -> Result<()> {
        let handle = self.handle.lock().map_err(|e| {
            crate::error::SimulatorError::InvalidOperation(format!("Lock poisoned: {e}"))
        })?;
        if let Some(cuda_handle) = *handle {
            // In real implementation: cudaStreamSynchronize(cuda_handle)
            Self::cuda_stream_synchronize(cuda_handle)?;
        }
        Ok(())
    }

    pub fn query(&self) -> Result<bool> {
        let handle = self.handle.lock().map_err(|e| {
            crate::error::SimulatorError::InvalidOperation(format!("Lock poisoned: {e}"))
        })?;
        if let Some(cuda_handle) = *handle {
            // In real implementation: cudaStreamQuery(cuda_handle)
            Self::cuda_stream_query(cuda_handle)
        } else {
            Ok(true) // Stream is ready if not created
        }
    }

    pub fn record_event(&self, event: &mut CudaEvent) -> Result<()> {
        let handle = self.handle.lock().map_err(|e| {
            crate::error::SimulatorError::InvalidOperation(format!("Lock poisoned: {e}"))
        })?;
        if let Some(cuda_handle) = *handle {
            // In real implementation: cudaEventRecord(event, cuda_handle)
            Self::cuda_event_record(*event, cuda_handle)?;
        }
        Ok(())
    }

    pub fn wait_event(&self, event: CudaEvent) -> Result<()> {
        let handle = self.handle.lock().map_err(|e| {
            crate::error::SimulatorError::InvalidOperation(format!("Lock poisoned: {e}"))
        })?;
        if let Some(cuda_handle) = *handle {
            // In real implementation: cudaStreamWaitEvent(cuda_handle, event, 0)
            Self::cuda_stream_wait_event(cuda_handle, event)?;
        }
        Ok(())
    }

    pub fn is_ready(&self) -> Result<bool> {
        self.query()
    }

    fn allocate_stream_id() -> usize {
        use std::sync::atomic::{AtomicUsize, Ordering};
        static STREAM_COUNTER: AtomicUsize = AtomicUsize::new(0);
        STREAM_COUNTER.fetch_add(1, Ordering::SeqCst)
    }

    fn create_cuda_stream(
        priority: StreamPriority,
        flags: StreamFlags,
    ) -> Result<Option<CudaStreamHandle>> {
        // In real implementation: cudaStreamCreateWithPriority
        let _priority_val = match priority {
            StreamPriority::Low => -1,
            StreamPriority::Normal => 0,
            StreamPriority::High => 1,
        };
        let _flags_val = match flags {
            StreamFlags::Default => 0,
            StreamFlags::NonBlocking => 1,
        };

        // Simulate stream creation
        Ok(Some(Self::allocate_stream_id()))
    }

    fn cuda_stream_synchronize(_handle: CudaStreamHandle) -> Result<()> {
        // Placeholder for actual CUDA synchronization
        std::thread::sleep(std::time::Duration::from_micros(10));
        Ok(())
    }

    fn cuda_stream_query(_handle: CudaStreamHandle) -> Result<bool> {
        // Placeholder for actual CUDA stream query
        Ok(true)
    }

    fn cuda_event_record(_event: CudaEvent, _stream: CudaStreamHandle) -> Result<()> {
        // Placeholder for actual CUDA event recording
        Ok(())
    }

    fn cuda_stream_wait_event(_stream: CudaStreamHandle, _event: CudaEvent) -> Result<()> {
        // Placeholder for actual CUDA stream wait event
        Ok(())
    }

    pub fn get_handle(&self) -> Arc<Mutex<Option<CudaStreamHandle>>> {
        Arc::clone(&self.handle)
    }

    pub fn get_handle_value(&self) -> Option<CudaStreamHandle> {
        let handle = self.handle.lock().ok()?;
        *handle
    }
}

#[cfg(feature = "advanced_math")]
impl Drop for CudaStream {
    fn drop(&mut self) {
        if let Ok(handle) = self.handle.lock() {
            if let Some(cuda_handle) = *handle {
                let _ = Self::cuda_stream_destroy(cuda_handle);
            }
        }
        // If lock is poisoned, we silently skip cleanup to avoid panic in Drop
    }
}

#[cfg(feature = "advanced_math")]
impl CudaStream {
    fn cuda_stream_destroy(_handle: CudaStreamHandle) -> Result<()> {
        // In real implementation: cudaStreamDestroy
        Ok(())
    }
}

/// Stream pool for managing multiple CUDA streams
#[cfg(feature = "advanced_math")]
pub struct CudaStreamPool {
    streams: Vec<CudaStream>,
    current_index: std::sync::atomic::AtomicUsize,
}

#[cfg(feature = "advanced_math")]
impl CudaStreamPool {
    pub fn new(num_streams: usize) -> Result<Self> {
        let mut streams = Vec::new();
        for _ in 0..num_streams {
            streams.push(CudaStream::new()?);
        }

        Ok(Self {
            streams,
            current_index: std::sync::atomic::AtomicUsize::new(0),
        })
    }

    pub fn get_next_stream(&self) -> &CudaStream {
        let index = self
            .current_index
            .fetch_add(1, std::sync::atomic::Ordering::SeqCst);
        &self.streams[index % self.streams.len()]
    }

    pub fn get_stream(&self, index: usize) -> Option<&CudaStream> {
        self.streams.get(index)
    }

    pub fn synchronize_all(&self) -> Result<()> {
        for stream in &self.streams {
            stream.synchronize()?;
        }
        Ok(())
    }

    pub fn len(&self) -> usize {
        self.streams.len()
    }

    pub fn is_empty(&self) -> bool {
        self.streams.is_empty()
    }
}