rtx-cfd legacy GPU: buffers re-borrowed after nested device calls; writing and delegating methods take &mut self

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(&mut self) -> CfdResult<()> {
         let buffers = self
             .gpu_buffers
-            .as_mut()
+            .as_ref()
             .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         let omega = 1.0 / self.params.tau;
@@ -375,6 +375,10 @@ __global__ void d3q19_bounce_back_boundaries(
 
         // Step 2: Compute equilibrium distributions
         self.gpu_compute_equilibrium()?;
+        let buffers = self
+            .gpu_buffers
+            .as_mut()
+            .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         // Step 3: Perform BGK collision
         let module = self
@@ -606,7 +610,7 @@ __global__ void d3q19_bounce_back_boundaries(
     }
 
     /// Complete GPU LBM time step
-    pub fn gpu_step(&self) -> CfdResult<()> {
+    pub fn gpu_step(&mut self) -> CfdResult<()> {
         self.gpu_collision_step()?;
         self.gpu_streaming_step()?;
         self.gpu_apply_bounce_back_boundaries()?;
@@ -667,8 +671,7 @@ __global__ void d3q19_bounce_back_boundaries(
     }
 
     /// Get macroscopic variables at a specific point (copy from GPU)
-    pub fn gpu_macroscopic_variables_at(
-        &self,
+    pub fn gpu_macroscopic_variables_at(&mut self,
         x: usize,
         y: usize,
         z: usize,
@@ -680,6 +683,10 @@ __global__ void d3q19_bounce_back_boundaries(
 
         // Extract macroscopic variables first
         self.gpu_extract_macroscopic_variables()?;
+        let buffers = self
+            .gpu_buffers
+            .as_ref()
+            .ok_or_else(|| CfdError::gpu_error("GPU buffers not initialized"))?;
 
         // Copy arrays from GPU
         let density_host = self.kernel_manager.copy_from_device(&buffers.density)?;
@@ -723,7 +730,7 @@ __global__ void d3q19_bounce_back_boundaries(
     }
 
     /// Calculate total mass on GPU
-    pub fn gpu_total_mass(&self) -> CfdResult<f64> {
+    pub fn gpu_total_mass(&mut self) -> CfdResult<f64> {
         let buffers = self
             .gpu_buffers
             .as_ref()
@@ -736,7 +743,7 @@ __global__ void d3q19_bounce_back_boundaries(
     }
 
     /// Calculate kinetic energy on GPU
-    pub fn gpu_kinetic_energy(&self) -> CfdResult<f64> {
+    pub fn gpu_kinetic_energy(&mut self) -> CfdResult<f64> {
         let buffers = self
             .gpu_buffers
             .as_ref()