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2026-03-04 00:08:42 +00:00
commit 4d88dc0584
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+//! GPU-accelerated Smagorinsky LES turbulence model
+//!
+//! This module provides CUDA-accelerated implementation of the Smagorinsky
+//! subgrid-scale model for Large Eddy Simulation (LES).
+
+use super::SmagorinskyConstants;
+use crate::kernels::CudaKernelManager;
+use crate::{CfdConfig, CfdError, CfdResult};
+use cudarc::driver::{CudaModule, CudaSlice, LaunchConfig, PushKernelArg};
+use std::sync::Arc;
+
+/// GPU memory buffers for Smagorinsky model
+struct SmagorinskyGpuBuffers {
+    /// Grid dimensions
+    nx: usize,
+    ny: usize,
+    nz: usize,
+
+    /// Filter width
+    delta: CudaSlice<f32>,
+
+    /// Velocity gradients
+    dudx: CudaSlice<f32>,
+    dudy: CudaSlice<f32>,
+    dudz: CudaSlice<f32>,
+    dvdx: CudaSlice<f32>,
+    dvdy: CudaSlice<f32>,
+    dvdz: CudaSlice<f32>,
+    dwdx: CudaSlice<f32>,
+    dwdy: CudaSlice<f32>,
+    dwdz: CudaSlice<f32>,
+
+    /// Strain rate tensor magnitude |S|
+    strain_rate: CudaSlice<f32>,
+
+    /// Subgrid-scale viscosity
+    sgs_viscosity: CudaSlice<f32>,
+
+    /// Temporary arrays
+    temp1: CudaSlice<f32>,
+    temp2: CudaSlice<f32>,
+}
+
+/// GPU-accelerated Smagorinsky SGS model for LES
+pub struct SmagorinskyGpuModel {
+    /// GPU kernel manager
+    kernel_manager: Arc<CudaKernelManager>,
+    /// Model constants
+    constants: SmagorinskyConstants,
+    /// Smagorinsky CUDA module
+    smagorinsky_module: Option<Arc<CudaModule>>,
+    /// GPU memory buffers
+    gpu_buffers: Option<SmagorinskyGpuBuffers>,
+}
+
+impl SmagorinskyGpuModel {
+    /// Create new Smagorinsky GPU model
+    pub fn new(config: &CfdConfig) -> CfdResult<Self> {
+        let kernel_manager = Arc::new(CudaKernelManager::new(config)?);
+
+        Ok(Self {
+            kernel_manager,
+            constants: SmagorinskyConstants::default(),
+            smagorinsky_module: None,
+            gpu_buffers: None,
+        })
+    }
+
+    /// Initialize model with grid dimensions
+    pub fn initialize(&mut self, nx: usize, ny: usize, nz: usize) -> CfdResult<()> {
+        // Load Smagorinsky kernels
+        self.load_smagorinsky_kernels()?;
+
+        // Allocate GPU buffers
+        self.allocate_gpu_buffers(nx, ny, nz)?;
+
+        Ok(())
+    }
+
+    /// Load and compile Smagorinsky CUDA kernels
+    fn load_smagorinsky_kernels(&mut self) -> CfdResult<()> {
+        // In real implementation, would compile or load PTX for Smagorinsky kernels
+        self.smagorinsky_module = Some(self.kernel_manager.get_module("smagorinsky_kernels")?);
+        Ok(())
+    }
+
+    /// Allocate GPU memory buffers
+    fn allocate_gpu_buffers(&mut self, nx: usize, ny: usize, nz: usize) -> CfdResult<()> {
+        let n = nx * ny * nz;
+
+        let buffers = SmagorinskyGpuBuffers {
+            nx,
+            ny,
+            nz,
+            delta: self.kernel_manager.allocate_f32(n)?,
+            dudx: self.kernel_manager.allocate_f32(n)?,
+            dudy: self.kernel_manager.allocate_f32(n)?,
+            dudz: self.kernel_manager.allocate_f32(n)?,
+            dvdx: self.kernel_manager.allocate_f32(n)?,
+            dvdy: self.kernel_manager.allocate_f32(n)?,
+            dvdz: self.kernel_manager.allocate_f32(n)?,
+            dwdx: self.kernel_manager.allocate_f32(n)?,
+            dwdy: self.kernel_manager.allocate_f32(n)?,
+            dwdz: self.kernel_manager.allocate_f32(n)?,
+            strain_rate: self.kernel_manager.allocate_f32(n)?,
+            sgs_viscosity: self.kernel_manager.allocate_f32(n)?,
+            temp1: self.kernel_manager.allocate_f32(n)?,
+            temp2: self.kernel_manager.allocate_f32(n)?,
+        };
+
+        self.gpu_buffers = Some(buffers);
+        Ok(())
+    }
+
+    /// Compute filter width on GPU
+    pub fn compute_filter_width(&mut self, dx: f32, dy: f32, dz: f32) -> CfdResult<()> {
+        let buffers = self
+            .gpu_buffers
+            .as_mut()
+            .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
+
+        let module = self
+            .smagorinsky_module
+            .as_ref()
+            .ok_or_else(|| CfdError::gpu_error("Smagorinsky module not loaded"))?;
+        let func = module.load_function("compute_filter_width").map_err(|e| {
+            CfdError::gpu_error(&format!("Failed to get filter width kernel: {}", e))
+        })?;
+
+        let grid_dim_x = (buffers.nx as u32 + 7) / 8;
+        let grid_dim_y = (buffers.ny as u32 + 7) / 8;
+        let grid_dim_z = (buffers.nz as u32 + 7) / 8;
+
+        let config = LaunchConfig {
+            grid_dim: (grid_dim_x, grid_dim_y, grid_dim_z),
+            block_dim: (8, 8, 8),
+            shared_mem_bytes: 0,
+        };
+
+        unsafe {
+            self.kernel_manager
+                .stream()
+                .launch_builder(&func)
+                .arg(&mut buffers.delta)
+                .arg(&dx)
+                .arg(&dy)
+                .arg(&dz)
+                .arg(&(buffers.nx as i32))
+                .arg(&(buffers.ny as i32))
+                .arg(&(buffers.nz as i32))
+                .launch(config)
+                .map_err(|e| {
+                    CfdError::gpu_error(&format!("Filter width kernel launch failed: {}", e))
+                })?;
+        }
+
+        self.kernel_manager.synchronize()?;
+        Ok(())
+    }
+
+    /// Compute SGS viscosity using Smagorinsky model
+    pub fn compute_sgs_viscosity(
+        &mut self,
+        u: &CudaSlice<f32>,
+        v: &CudaSlice<f32>,
+        w: &CudaSlice<f32>,
+        dx: f32,
+        dy: f32,
+        dz: f32,
+    ) -> CfdResult<()> {
+        // Step 1: Compute velocity gradients
+        self.compute_velocity_gradients(u, v, w, dx, dy, dz)?;
+
+        // Step 2: Compute strain rate magnitude
+        self.compute_strain_rate_magnitude()?;
+
+        // Step 3: Compute SGS viscosity = (Cs * delta)^2 * |S|
+        self.compute_sgs_viscosity_from_strain()?;
+
+        Ok(())
+    }
+
+    /// Compute velocity gradients on GPU
+    fn compute_velocity_gradients(
+        &mut self,
+        u: &CudaSlice<f32>,
+        v: &CudaSlice<f32>,
+        w: &CudaSlice<f32>,
+        dx: f32,
+        dy: f32,
+        dz: f32,
+    ) -> CfdResult<()> {
+        let buffers = self
+            .gpu_buffers
+            .as_mut()
+            .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
+
+        let module = self
+            .smagorinsky_module
+            .as_ref()
+            .ok_or_else(|| CfdError::gpu_error("Smagorinsky module not loaded"))?;
+        let func = module
+            .load_function("compute_velocity_gradients")
+            .map_err(|e| {
+                CfdError::gpu_error(&format!("Failed to get velocity gradients kernel: {}", e))
+            })?;
+
+        let grid_dim_x = (buffers.nx as u32 + 7) / 8;
+        let grid_dim_y = (buffers.ny as u32 + 7) / 8;
+        let grid_dim_z = (buffers.nz as u32 + 7) / 8;
+
+        let config = LaunchConfig {
+            grid_dim: (grid_dim_x, grid_dim_y, grid_dim_z),
+            block_dim: (8, 8, 8),
+            shared_mem_bytes: 0,
+        };
+
+        unsafe {
+            self.kernel_manager
+                .stream()
+                .launch_builder(&func)
+                .arg(u)
+                .arg(v)
+                .arg(w)
+                .arg(&mut buffers.dudx)
+                .arg(&mut buffers.dudy)
+                .arg(&mut buffers.dudz)
+                .arg(&mut buffers.dvdx)
+                .arg(&mut buffers.dvdy)
+                .arg(&mut buffers.dvdz)
+                .arg(&mut buffers.dwdx)
+                .arg(&mut buffers.dwdy)
+                .arg(&mut buffers.dwdz)
+                .arg(&dx)
+                .arg(&dy)
+                .arg(&dz)
+                .arg(&(buffers.nx as i32))
+                .arg(&(buffers.ny as i32))
+                .arg(&(buffers.nz as i32))
+                .launch(config)
+                .map_err(|e| {
+                    CfdError::gpu_error(&format!("Velocity gradients kernel launch failed: {}", e))
+                })?;
+        }
+
+        Ok(())
+    }
+
+    /// Compute strain rate magnitude |S|
+    fn compute_strain_rate_magnitude(&mut self) -> CfdResult<()> {
+        let buffers = self
+            .gpu_buffers
+            .as_mut()
+            .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
+
+        let module = self
+            .smagorinsky_module
+            .as_ref()
+            .ok_or_else(|| CfdError::gpu_error("Smagorinsky module not loaded"))?;
+        let func = module
+            .load_function("compute_strain_rate_magnitude")
+            .map_err(|e| {
+                CfdError::gpu_error(&format!("Failed to get strain rate kernel: {}", e))
+            })?;
+
+        let grid_dim_x = (buffers.nx as u32 + 7) / 8;
+        let grid_dim_y = (buffers.ny as u32 + 7) / 8;
+        let grid_dim_z = (buffers.nz as u32 + 7) / 8;
+
+        let config = LaunchConfig {
+            grid_dim: (grid_dim_x, grid_dim_y, grid_dim_z),
+            block_dim: (8, 8, 8),
+            shared_mem_bytes: 0,
+        };
+
+        unsafe {
+            self.kernel_manager
+                .stream()
+                .launch_builder(&func)
+                .arg(&buffers.dudx)
+                .arg(&buffers.dudy)
+                .arg(&buffers.dudz)
+                .arg(&buffers.dvdx)
+                .arg(&buffers.dvdy)
+                .arg(&buffers.dvdz)
+                .arg(&buffers.dwdx)
+                .arg(&buffers.dwdy)
+                .arg(&buffers.dwdz)
+                .arg(&mut buffers.strain_rate)
+                .arg(&(buffers.nx as i32))
+                .arg(&(buffers.ny as i32))
+                .arg(&(buffers.nz as i32))
+                .launch(config)
+                .map_err(|e| {
+                    CfdError::gpu_error(&format!("Strain rate kernel launch failed: {}", e))
+                })?;
+        }
+
+        Ok(())
+    }
+
+    /// Compute SGS viscosity from strain rate
+    fn compute_sgs_viscosity_from_strain(&mut self) -> CfdResult<()> {
+        let buffers = self
+            .gpu_buffers
+            .as_mut()
+            .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
+
+        let module = self
+            .smagorinsky_module
+            .as_ref()
+            .ok_or_else(|| CfdError::gpu_error("Smagorinsky module not loaded"))?;
+        let func = module.load_function("compute_sgs_viscosity").map_err(|e| {
+            CfdError::gpu_error(&format!("Failed to get SGS viscosity kernel: {}", e))
+        })?;
+
+        let grid_dim_x = (buffers.nx as u32 + 7) / 8;
+        let grid_dim_y = (buffers.ny as u32 + 7) / 8;
+        let grid_dim_z = (buffers.nz as u32 + 7) / 8;
+
+        let config = LaunchConfig {
+            grid_dim: (grid_dim_x, grid_dim_y, grid_dim_z),
+            block_dim: (8, 8, 8),
+            shared_mem_bytes: 0,
+        };
+
+        unsafe {
+            self.kernel_manager
+                .stream()
+                .launch_builder(&func)
+                .arg(&buffers.strain_rate)
+                .arg(&buffers.delta)
+                .arg(&mut buffers.sgs_viscosity)
+                .arg(&self.constants.cs)
+                .arg(&(buffers.nx as i32))
+                .arg(&(buffers.ny as i32))
+                .arg(&(buffers.nz as i32))
+                .launch(config)
+                .map_err(|e| {
+                    CfdError::gpu_error(&format!("SGS viscosity kernel launch failed: {}", e))
+                })?;
+        }
+
+        self.kernel_manager.synchronize()?;
+        Ok(())
+    }
+
+    /// Get SGS viscosity field from GPU
+    pub fn get_sgs_viscosity(&self) -> CfdResult<Vec<f32>> {
+        let buffers = self
+            .gpu_buffers
+            .as_ref()
+            .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
+
+        let n = buffers.nx * buffers.ny * buffers.nz;
+        let mut sgs_viscosity_host = vec![0.0f32; n];
+
+        self.kernel_manager
+            .stream
+            .memcpy_dtoh(&buffers.sgs_viscosity, &mut sgs_viscosity_host)
+            .map_err(|e| {
+                CfdError::gpu_error(&format!("Failed to copy SGS viscosity from GPU: {}", e))
+            })?;
+
+        self.kernel_manager.synchronize()?;
+        Ok(sgs_viscosity_host)
+    }
+}