// Copyright (c) 2024 RustyTorch Team // Licensed under MIT OR Apache-2.0 //! GPU Backend Abstraction for CFD Operations //! //! This module provides a backend-agnostic interface for GPU-accelerated CFD kernels, //! supporting both CUDA (NVIDIA) and Metal (Apple Silicon) backends. //! //! # Architecture //! //! ```text //! GpuBackend trait //! ├── CudaBackend (NVIDIA GPUs via cudarc) //! └── MetalBackend (Apple Silicon via rtx-metal) //! ``` //! //! # Example //! //! ```rust,ignore //! let backend = GpuBackend::auto_detect()?; //! let buffer = backend.allocate::(1024)?; //! backend.launch_kernel("poisson_jacobi", config, &[buffer])?; //! ``` use crate::error::CfdResult; use std::sync::Arc; /// Configuration for kernel launches #[derive(Debug, Clone)] pub struct LaunchConfig { /// Grid dimensions (width, height, depth) pub grid: (usize, usize, usize), /// Thread group / block dimensions pub block: (usize, usize, usize), /// Shared memory size in bytes pub shared_memory: usize, } impl LaunchConfig { /// Create a 1D launch configuration pub fn new_1d(n: usize, block_size: usize) -> Self { let grid = (n + block_size - 1) / block_size; Self { grid: (grid, 1, 1), block: (block_size, 1, 1), shared_memory: 0, } } /// Create a 2D launch configuration pub fn new_2d(nx: usize, ny: usize, block_x: usize, block_y: usize) -> Self { let grid_x = (nx + block_x - 1) / block_x; let grid_y = (ny + block_y - 1) / block_y; Self { grid: (grid_x, grid_y, 1), block: (block_x, block_y, 1), shared_memory: 0, } } /// Create a 3D launch configuration pub fn new_3d( nx: usize, ny: usize, nz: usize, block_x: usize, block_y: usize, block_z: usize, ) -> Self { let grid_x = (nx + block_x - 1) / block_x; let grid_y = (ny + block_y - 1) / block_y; let grid_z = (nz + block_z - 1) / block_z; Self { grid: (grid_x, grid_y, grid_z), block: (block_x, block_y, block_z), shared_memory: 0, } } /// Set shared memory size pub fn with_shared_memory(mut self, size: usize) -> Self { self.shared_memory = size; self } } /// GPU buffer handle - opaque type for backend-specific storage pub struct GpuBuffer { /// Buffer ID for the backend pub id: usize, /// Size in elements pub len: usize, /// Element size in bytes pub element_size: usize, } impl GpuBuffer { /// Get total size in bytes pub fn size_bytes(&self) -> usize { self.len * self.element_size } } /// Backend type enumeration #[derive(Debug, Clone, Copy, PartialEq, Eq)] pub enum BackendType { /// NVIDIA CUDA backend Cuda, /// Apple Metal backend Metal, /// CPU fallback Cpu, } impl std::fmt::Display for BackendType { fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { match self { BackendType::Cuda => write!(f, "CUDA"), BackendType::Metal => write!(f, "Metal"), BackendType::Cpu => write!(f, "CPU"), } } } /// GPU Backend trait for CFD operations /// /// This trait abstracts the underlying GPU framework (CUDA/Metal), /// providing a unified interface for CFD kernel execution. pub trait GpuBackend: Send + Sync { /// Get the backend type fn backend_type(&self) -> BackendType; /// Get device name fn device_name(&self) -> &str; /// Check if backend is available fn is_available(&self) -> bool; /// Allocate a buffer on the device fn allocate(&self, len: usize, element_size: usize) -> CfdResult; /// Free a buffer fn free(&self, buffer: &GpuBuffer) -> CfdResult<()>; /// Copy data from host to device fn copy_to_device(&self, buffer: &GpuBuffer, data: &[u8]) -> CfdResult<()>; /// Copy data from device to host fn copy_to_host(&self, buffer: &GpuBuffer, data: &mut [u8]) -> CfdResult<()>; /// Synchronize all pending operations fn synchronize(&self) -> CfdResult<()>; /// Get maximum threads per block/threadgroup fn max_threads_per_block(&self) -> usize; /// Get device memory size in bytes fn device_memory(&self) -> usize; } /// CPU fallback backend for testing and non-GPU systems pub struct CpuBackend { name: String, } impl CpuBackend { /// Create a new CPU backend pub fn new() -> Self { Self { name: "CPU".to_string(), } } } impl Default for CpuBackend { fn default() -> Self { Self::new() } } impl GpuBackend for CpuBackend { fn backend_type(&self) -> BackendType { BackendType::Cpu } fn device_name(&self) -> &str { &self.name } fn is_available(&self) -> bool { true } fn allocate(&self, len: usize, element_size: usize) -> CfdResult { Ok(GpuBuffer { id: 0, len, element_size, }) } fn free(&self, _buffer: &GpuBuffer) -> CfdResult<()> { Ok(()) } fn copy_to_device(&self, _buffer: &GpuBuffer, _data: &[u8]) -> CfdResult<()> { Ok(()) } fn copy_to_host(&self, _buffer: &GpuBuffer, _data: &mut [u8]) -> CfdResult<()> { Ok(()) } fn synchronize(&self) -> CfdResult<()> { Ok(()) } fn max_threads_per_block(&self) -> usize { 1 } fn device_memory(&self) -> usize { // Return approximate available system memory 8 * 1024 * 1024 * 1024 // 8 GB default } } /// Auto-detect and create the best available GPU backend pub fn auto_detect_backend() -> Arc { // Try CUDA first (on any platform) #[cfg(feature = "cuda")] { // TODO: Implement CUDA backend detection tracing::info!("CUDA feature enabled but backend not yet implemented"); } // Try Metal on macOS #[cfg(all(target_os = "macos", feature = "metal"))] { use rtx_metal::MetalDevice; if MetalDevice::is_available() { tracing::info!("Metal backend available"); // TODO: Create and return Metal backend } } // Fallback to CPU tracing::info!("Using CPU fallback backend"); Arc::new(CpuBackend::new()) } #[cfg(test)] mod tests { use super::*; #[test] fn test_launch_config_1d() { let config = LaunchConfig::new_1d(1024, 256); assert_eq!(config.grid, (4, 1, 1)); assert_eq!(config.block, (256, 1, 1)); } #[test] fn test_launch_config_2d() { let config = LaunchConfig::new_2d(64, 64, 16, 16); assert_eq!(config.grid, (4, 4, 1)); assert_eq!(config.block, (16, 16, 1)); } #[test] fn test_cpu_backend() { let backend = CpuBackend::new(); assert_eq!(backend.backend_type(), BackendType::Cpu); assert!(backend.is_available()); } #[test] fn test_auto_detect() { let backend = auto_detect_backend(); assert!(backend.is_available()); } }