rtx-cfd legacy GPU: kernel outputs were device-buffer CLONES (every write lost) — the buffers are borrowed mutably now; the Poisson kernels keep boundary Dirichlet values; tests: the advection pulse marched 50 steps, the Jacobi budget 20k, the reduction reference in f64

crates/specialized/rtx-cfd/src/kernels/cuda/poisson.cu

@@ -25,9 +25,9 @@ extern "C" __global__ void poisson_jacobi_2d(
 
     int idx = j * nx + i;
 
-    // Boundary conditions (Dirichlet - zero on boundaries for now)
+    // Boundary cells keep the Dirichlet values they hold.
     if (i == 0 || i == nx - 1 || j == 0 || j == ny - 1) {
-        phi_new[idx] = 0.0f;
+        phi_new[idx] = phi[idx];
         return;
     }
 
@@ -66,7 +66,6 @@ extern "C" __global__ void poisson_gauss_seidel_2d(
 
     // Boundary conditions
     if (i == 0 || i == nx - 1 || j == 0 || j == ny - 1) {
-        phi[idx] = 0.0f;
         return;
     }
 
@@ -105,7 +104,6 @@ extern "C" __global__ void poisson_sor_2d(
 
     // Boundary conditions
     if (i == 0 || i == nx - 1 || j == 0 || j == ny - 1) {
-        phi[idx] = 0.0f;
         return;
     }
 

crates/specialized/rtx-cfd/src/solvers/incompressible/piso_gpu.rs

@@ -147,7 +147,7 @@ impl PisoGpuSolver {
     fn copy_to_gpu(&self, flow_field: &FlowField) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         // Convert nalgebra matrices to flat vectors
@@ -171,7 +171,7 @@ impl PisoGpuSolver {
     fn copy_from_gpu(&self, flow_field: &mut FlowField) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         // Copy from GPU
@@ -271,7 +271,7 @@ impl PisoGpuSolver {
         let (nx, ny) = {
             let buffers = self
                 .gpu_buffers
-                .as_ref()
+                .as_mut()
                 .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
             (buffers.nx, buffers.ny)
         };
@@ -313,7 +313,7 @@ impl PisoGpuSolver {
         let residual_norm = {
             let buffers = self
                 .gpu_buffers
-                .as_ref()
+                .as_mut()
                 .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
             self.matrix_ops_kernel.vector_norm(&buffers.mass_source)?
         };
@@ -464,8 +464,8 @@ impl PisoGpuSolver {
                 .stream()
                 .launch_builder(&func)
                 .arg(&buffers.pressure_correction)
-                .arg(&mut buffers.u_correction.clone())
+                .arg(&mut buffers.u_correction)
-                .arg(&mut buffers.v_correction.clone())
+                .arg(&mut buffers.v_correction)
                 .arg(&correction_factor)
                 .arg(&dx)
                 .arg(&dy)

crates/specialized/rtx-cfd/src/solvers/incompressible/simple_gpu.rs

@@ -136,7 +136,7 @@ impl SimpleGpuSolver {
     fn copy_to_gpu(&self, flow_field: &FlowField) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         // Convert nalgebra matrices to flat vectors
@@ -163,7 +163,7 @@ impl SimpleGpuSolver {
     fn copy_from_gpu(&self, flow_field: &mut FlowField) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         // Copy from GPU
@@ -300,7 +300,7 @@ impl SimpleGpuSolver {
     async fn gpu_pressure_update(&self, pressure_relaxation: f32) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         // p = p + α_p * p'  (pressure update with relaxation)

crates/specialized/rtx-cfd/src/solvers/lbm/d2q9_gpu.rs

@@ -256,7 +256,7 @@ impl D2Q9GpuSolver {
     fn gpu_collision_step(&self) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         // First compute equilibrium distributions
@@ -284,7 +284,7 @@ impl D2Q9GpuSolver {
             self.kernel_manager
                 .stream()
                 .launch_builder(&func)
-                .arg(&mut buffers.f.clone())
+                .arg(&mut buffers.f)
                 .arg(&buffers.f_eq)
                 .arg(&(self.omega as f32))
                 .arg(&(buffers.nx as i32))
@@ -303,7 +303,7 @@ impl D2Q9GpuSolver {
     pub fn gpu_streaming_step(&self) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         let module = self
@@ -327,7 +327,7 @@ impl D2Q9GpuSolver {
             self.kernel_manager
                 .stream()
                 .launch_builder(&func)
-                .arg(&mut buffers.f_temp.clone())
+                .arg(&mut buffers.f_temp)
                 .arg(&buffers.f)
                 .arg(&(buffers.nx as i32))
                 .arg(&(buffers.ny as i32))
@@ -347,7 +347,7 @@ impl D2Q9GpuSolver {
     fn gpu_compute_macroscopic(&self) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         let module = self
@@ -371,9 +371,9 @@ impl D2Q9GpuSolver {
             self.kernel_manager
                 .stream()
                 .launch_builder(&func)
-                .arg(&mut buffers.density.clone())
+                .arg(&mut buffers.density)
-                .arg(&mut buffers.velocity_x.clone())
+                .arg(&mut buffers.velocity_x)
-                .arg(&mut buffers.velocity_y.clone())
+                .arg(&mut buffers.velocity_y)
                 .arg(&buffers.f)
                 .arg(&(buffers.nx as i32))
                 .arg(&(buffers.ny as i32))
@@ -394,7 +394,7 @@ impl D2Q9GpuSolver {
     fn gpu_compute_equilibrium(&self) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         let module = self
@@ -418,7 +418,7 @@ impl D2Q9GpuSolver {
             self.kernel_manager
                 .stream()
                 .launch_builder(&func)
-                .arg(&mut buffers.f_eq.clone())
+                .arg(&mut buffers.f_eq)
                 .arg(&buffers.density)
                 .arg(&buffers.velocity_x)
                 .arg(&buffers.velocity_y)
@@ -438,7 +438,7 @@ impl D2Q9GpuSolver {
     pub fn gpu_apply_bounce_back_boundaries(&self) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         let module = self
@@ -462,7 +462,7 @@ impl D2Q9GpuSolver {
             self.kernel_manager
                 .stream()
                 .launch_builder(&func)
-                .arg(&mut buffers.f.clone())
+                .arg(&mut buffers.f)
                 .arg(&(buffers.nx as i32))
                 .arg(&(buffers.ny as i32))
                 .launch(config)
@@ -492,7 +492,7 @@ impl D2Q9GpuSolver {
     ) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         let module = self
@@ -516,10 +516,10 @@ impl D2Q9GpuSolver {
             self.kernel_manager
                 .stream()
                 .launch_builder(&func)
-                .arg(&mut buffers.f.clone())
+                .arg(&mut buffers.f)
-                .arg(&mut buffers.density.clone())
+                .arg(&mut buffers.density)
-                .arg(&mut buffers.velocity_x.clone())
+                .arg(&mut buffers.velocity_x)
-                .arg(&mut buffers.velocity_y.clone())
+                .arg(&mut buffers.velocity_y)
                 .arg(&(density as f32))
                 .arg(&(velocity.x as f32))
                 .arg(&(velocity.y as f32))
@@ -539,7 +539,7 @@ impl D2Q9GpuSolver {
     pub fn get_macroscopic_at(&self, i: usize, j: usize) -> CfdResult<(f64, Vector2<f64>)> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         let idx = j * buffers.nx + i;
@@ -585,7 +585,7 @@ impl D2Q9GpuSolver {
     pub fn update_flow_field(&self, flow_field: &mut FlowField) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         let (nx, ny, _, _) = flow_field.grid_info();

crates/specialized/rtx-cfd/src/solvers/lbm/d3q19_gpu.rs

@@ -365,7 +365,7 @@ __global__ void d3q19_bounce_back_boundaries(
     pub fn gpu_collision_step(&self) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         let omega = 1.0 / self.params.tau;
@@ -399,7 +399,7 @@ __global__ void d3q19_bounce_back_boundaries(
             self.kernel_manager
                 .stream()
                 .launch_builder(&func)
-                .arg(&mut buffers.f.clone())
+                .arg(&mut buffers.f)
                 .arg(&buffers.f_eq)
                 .arg(&(omega as f32))
                 .arg(&(buffers.nx as i32))
@@ -419,7 +419,7 @@ __global__ void d3q19_bounce_back_boundaries(
     pub fn gpu_streaming_step(&self) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         let module = self
@@ -444,7 +444,7 @@ __global__ void d3q19_bounce_back_boundaries(
             self.kernel_manager
                 .stream()
                 .launch_builder(&func)
-                .arg(&mut buffers.f_temp.clone())
+                .arg(&mut buffers.f_temp)
                 .arg(&buffers.f)
                 .arg(&(buffers.nx as i32))
                 .arg(&(buffers.ny as i32))
@@ -465,7 +465,7 @@ __global__ void d3q19_bounce_back_boundaries(
     fn gpu_extract_macroscopic_variables(&self) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         let module = self
@@ -495,10 +495,10 @@ __global__ void d3q19_bounce_back_boundaries(
             self.kernel_manager
                 .stream()
                 .launch_builder(&func)
-                .arg(&mut buffers.density.clone())
+                .arg(&mut buffers.density)
-                .arg(&mut buffers.velocity_x.clone())
+                .arg(&mut buffers.velocity_x)
-                .arg(&mut buffers.velocity_y.clone())
+                .arg(&mut buffers.velocity_y)
-                .arg(&mut buffers.velocity_z.clone())
+                .arg(&mut buffers.velocity_z)
                 .arg(&buffers.f)
                 .arg(&(buffers.nx as i32))
                 .arg(&(buffers.ny as i32))
@@ -520,7 +520,7 @@ __global__ void d3q19_bounce_back_boundaries(
     fn gpu_compute_equilibrium(&self) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         let module = self
@@ -545,7 +545,7 @@ __global__ void d3q19_bounce_back_boundaries(
             self.kernel_manager
                 .stream()
                 .launch_builder(&func)
-                .arg(&mut buffers.f_eq.clone())
+                .arg(&mut buffers.f_eq)
                 .arg(&buffers.density)
                 .arg(&buffers.velocity_x)
                 .arg(&buffers.velocity_y)
@@ -567,7 +567,7 @@ __global__ void d3q19_bounce_back_boundaries(
     pub fn gpu_apply_bounce_back_boundaries(&self) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         let module = self
@@ -591,7 +591,7 @@ __global__ void d3q19_bounce_back_boundaries(
             self.kernel_manager
                 .stream()
                 .launch_builder(&func)
-                .arg(&mut buffers.f.clone())
+                .arg(&mut buffers.f)
                 .arg(&(buffers.nx as i32))
                 .arg(&(buffers.ny as i32))
                 .arg(&(buffers.nz as i32))
@@ -621,7 +621,7 @@ __global__ void d3q19_bounce_back_boundaries(
     ) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         let module = self
@@ -648,7 +648,7 @@ __global__ void d3q19_bounce_back_boundaries(
             self.kernel_manager
                 .stream()
                 .launch_builder(&func)
-                .arg(&mut buffers.f.clone())
+                .arg(&mut buffers.f)
                 .arg(&(density as f32))
                 .arg(&(velocity.x as f32))
                 .arg(&(velocity.y as f32))
@@ -675,7 +675,7 @@ __global__ void d3q19_bounce_back_boundaries(
     ) -> CfdResult<MacroscopicVariables3D> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         // Extract macroscopic variables first
@@ -726,7 +726,7 @@ __global__ void d3q19_bounce_back_boundaries(
     pub fn gpu_total_mass(&self) -> CfdResult<f64> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         self.gpu_extract_macroscopic_variables()?;
@@ -739,7 +739,7 @@ __global__ void d3q19_bounce_back_boundaries(
     pub fn gpu_kinetic_energy(&self) -> CfdResult<f64> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         self.gpu_extract_macroscopic_variables()?;

crates/specialized/rtx-cfd/src/turbulence/k_epsilon_gpu.rs

@@ -429,7 +429,7 @@ impl KEpsilonGpuModel {
     pub fn get_eddy_viscosity(&self) -> CfdResult<Vec<f32>> {
         let buffers = self
             .gpu_buffers
-            .as_ref()
+            .as_mut()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         let n = buffers.nx * buffers.ny * buffers.nz;

crates/specialized/rtx-cfd/tests/gpu_reduction_tests.rs

@@ -37,7 +37,7 @@ mod gpu_reduction_tests {
 
         // Create test data
         let test_data: Vec<f32> = (1..=100).map(|i| i as f32).collect();
-        let expected_sum = test_data.iter().sum::<f32>();
+        let expected_sum = test_data.iter().map(|&v| v as f64).sum::<f64>() as f32; // f64 reference: a sequential f32 sum of a million terms carries ~1e-3 of rounding
 
         // Copy to GPU
         let gpu_data = manager.copy_to_device(&test_data)?;
@@ -100,7 +100,7 @@ mod gpu_reduction_tests {
         // Create large test array
         let n = 1_000_000;
         let test_data: Vec<f32> = (0..n).map(|i| (i % 100) as f32).collect();
-        let expected_sum = test_data.iter().sum::<f32>();
+        let expected_sum = test_data.iter().map(|&v| v as f64).sum::<f64>() as f32; // f64 reference: a sequential f32 sum of a million terms carries ~1e-3 of rounding
 
         // Copy to GPU
         let gpu_data = manager.copy_to_device(&test_data)?;

crates/specialized/rtx-cfd/tests/kernels_tests.rs

@@ -46,17 +46,15 @@ mod cuda_tests {
         d_phi = kernel_manager.copy_to_device(&phi)?;
 
         // Run advection kernel
-        advection_kernel.apply(
+        // CFL = v dt / dx ≈ 0.1: march 50 steps so the pulse moves several cells.
-            &d_phi,
+        for _ in 0..50 {
-            &mut d_phi_new,
+            advection_kernel.apply(&d_phi, &mut d_phi_new, velocity as f32, dt as f32, dx as f32)?;
-            velocity as f32,
+            std::mem::swap(&mut d_phi, &mut d_phi_new);
-            dt as f32,
+        }
-            dx as f32,
-        )?;
 
         // Copy result back
         let mut result = vec![0.0f32; nx];
-        result = kernel_manager.copy_from_device(&d_phi_new)?;
+        result = kernel_manager.copy_from_device(&d_phi)?;
 
         // Verify that the pulse has moved (mass conservation)
         let initial_mass: f32 = phi.iter().sum();
@@ -206,7 +204,7 @@ mod cuda_tests {
         d_source = kernel_manager.copy_to_device(&source)?;
 
         // Solve Poisson equation
-        let max_iterations = 1000;
+        let max_iterations = 20_000; // Jacobi needs O(n²) sweeps on this grid
         let tolerance = 1e-6;
         let iterations = poisson_kernel.solve_2d(
             &mut d_phi,