rtx-cfd: the legacy GPU modules back in the cuda build (repair in progress)

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

@@ -4,9 +4,6 @@
 //! - SIMPLE (Semi-Implicit Method for Pressure Linked Equations)
 //! - PISO (Pressure-Implicit with Splitting of Operators)
 //! - SIMPLER (SIMPLE Revised)
-// PERF-2 (2026-09-16): the legacy GPU modules have not compiled since the
-// initial commit (cudarc API drift); kept out of the `cuda` build until
-// someone needs them — the batched V-cycle benchmark uses cudarc directly.
 
 use crate::{CfdConfig, CfdError, CfdResult};
 // use nalgebra::{DMatrix, DVector};
@@ -29,16 +26,16 @@ pub mod overset;
 /// PISO algorithm implementation
 pub mod piso;
 /// GPU-accelerated PISO algorithm implementation
-// #[cfg(feature = "cuda")]
-// pub mod piso_gpu;
+#[cfg(feature = "cuda")]
+pub mod piso_gpu;
 /// Five-point Poisson problems and the multigrid-preconditioned CG solver
 pub mod poisson;
 pub mod polygon_sdf;
 /// SIMPLE algorithm implementation
 pub mod simple;
 /// GPU-accelerated SIMPLE algorithm implementation
-// #[cfg(feature = "cuda")]
-// pub mod simple_gpu;
+#[cfg(feature = "cuda")]
+pub mod simple_gpu;
 /// CSR matrix + Jacobi-BiCGSTAB for the curvilinear pressure equation
 pub mod sparse_bicgstab;
 
@@ -65,8 +62,8 @@ pub use overset::{
     OversetResult, OversetSolverState, ResidualBucket, StepTimers,
 };
 pub use piso::{PisoParameters, PisoResult, PisoSolver};
-// #[cfg(feature = "cuda")]
-// pub use piso_gpu::PisoGpuSolver;
+#[cfg(feature = "cuda")]
+pub use piso_gpu::PisoGpuSolver;
 pub use poisson::{
     LevelExport, MgPrecision, MgSmoother, MultigridParameters, PcgCache, PoissonProblem,
     PoissonSolution, export_hierarchy, vcycle_f32_reference, vcycle_f32_work,
@@ -74,8 +71,8 @@ pub use poisson::{
 };
 pub use polygon_sdf::PolygonSdf;
 pub use simple::{ConvectionScheme, SimpleParameters, SimpleResult, SimpleSolver};
-// #[cfg(feature = "cuda")]
-// pub use simple_gpu::SimpleGpuSolver;
+#[cfg(feature = "cuda")]
+pub use simple_gpu::SimpleGpuSolver;
 
 /// Common solver parameters
 #[derive(Debug, Clone)]