From 175d637abe13ed60d65fbb4006f89eedc46ec429 Mon Sep 17 00:00:00 2001
From: Daniel Arndt <arndtd@ornl.gov>
Date: Sun, 2 Jul 2023 12:08:37 -0400
Subject: [PATCH] Allow running step-64 without CUDA

---
 examples/step-64/CMakeLists.txt |  4 +---
 examples/step-64/step-64.cc     | 39 ++++++++++++++-------------------
 2 files changed, 18 insertions(+), 25 deletions(-)

diff --git a/examples/step-64/CMakeLists.txt b/examples/step-64/CMakeLists.txt
index 879304a1ae..ff3748ceff 100644
--- a/examples/step-64/CMakeLists.txt
+++ b/examples/step-64/CMakeLists.txt
@@ -37,16 +37,14 @@ endif()
 #
 # Are all dependencies fulfilled?
 #
-if(NOT DEAL_II_WITH_MPI OR NOT DEAL_II_WITH_P4EST OR NOT DEAL_II_WITH_CUDA) # keep in one line
+if(NOT DEAL_II_WITH_MPI OR NOT DEAL_II_WITH_P4EST) # keep in one line
   message(FATAL_ERROR "
 Error! This tutorial requires a deal.II library that was configured with the following options:
     DEAL_II_WITH_MPI = ON
     DEAL_II_WITH_P4EST = ON
-    DEAL_II_WITH_CUDA = ON
 However, the deal.II library found at ${DEAL_II_PATH} was configured with these options:
     DEAL_II_WITH_MPI = ${DEAL_II_WITH_MPI}
     DEAL_II_WITH_P4EST = ${DEAL_II_WITH_P4EST}
-    DEAL_II_WITH_CUDA = ${DEAL_II_WITH_CUDA}
 This conflicts with the requirements."
     )
 endif()
diff --git a/examples/step-64/step-64.cc b/examples/step-64/step-64.cc
index c14134bb9f..dccfe9f9a6 100644
--- a/examples/step-64/step-64.cc
+++ b/examples/step-64/step-64.cc
@@ -131,7 +131,9 @@ namespace Step64
       const typename CUDAWrappers::MatrixFree<dim, double>::Data *gpu_data,
       double *                                                    coef,
       int                                                         cell)
-      : coef(coef)
+      : gpu_data(gpu_data)
+      , coef(coef)
+      , cell(cell)
     {}
 
     DEAL_II_HOST_DEVICE void operator()(
@@ -244,16 +246,17 @@ namespace Step64
                       const AffineConstraints<double> &constraints);
 
     void
-    vmult(LinearAlgebra::distributed::Vector<double, MemorySpace::CUDA> &dst,
-          const LinearAlgebra::distributed::Vector<double, MemorySpace::CUDA>
+    vmult(LinearAlgebra::distributed::Vector<double, MemorySpace::Default> &dst,
+          const LinearAlgebra::distributed::Vector<double, MemorySpace::Default>
             &src) const;
 
     void initialize_dof_vector(
-      LinearAlgebra::distributed::Vector<double, MemorySpace::CUDA> &vec) const;
+      LinearAlgebra::distributed::Vector<double, MemorySpace::Default> &vec)
+      const;
 
   private:
-    CUDAWrappers::MatrixFree<dim, double>       mf_data;
-    LinearAlgebra::CUDAWrappers::Vector<double> coef;
+    CUDAWrappers::MatrixFree<dim, double>                            mf_data;
+    LinearAlgebra::distributed::Vector<double, MemorySpace::Default> coef;
   };
 
 
@@ -307,8 +310,8 @@ namespace Step64
   // destination vector afterwards.
   template <int dim, int fe_degree>
   void HelmholtzOperator<dim, fe_degree>::vmult(
-    LinearAlgebra::distributed::Vector<double, MemorySpace::CUDA> &      dst,
-    const LinearAlgebra::distributed::Vector<double, MemorySpace::CUDA> &src)
+    LinearAlgebra::distributed::Vector<double, MemorySpace::Default> &      dst,
+    const LinearAlgebra::distributed::Vector<double, MemorySpace::Default> &src)
     const
   {
     dst = 0.;
@@ -322,7 +325,7 @@ namespace Step64
 
   template <int dim, int fe_degree>
   void HelmholtzOperator<dim, fe_degree>::initialize_dof_vector(
-    LinearAlgebra::distributed::Vector<double, MemorySpace::CUDA> &vec) const
+    LinearAlgebra::distributed::Vector<double, MemorySpace::Default> &vec) const
   {
     mf_data.initialize_dof_vector(vec);
   }
@@ -379,8 +382,9 @@ namespace Step64
     // can view and display the solution as usual.
     LinearAlgebra::distributed::Vector<double, MemorySpace::Host>
       ghost_solution_host;
-    LinearAlgebra::distributed::Vector<double, MemorySpace::CUDA> solution_dev;
-    LinearAlgebra::distributed::Vector<double, MemorySpace::CUDA>
+    LinearAlgebra::distributed::Vector<double, MemorySpace::Default>
+      solution_dev;
+    LinearAlgebra::distributed::Vector<double, MemorySpace::Default>
       system_rhs_dev;
 
     ConditionalOStream pcout;
@@ -517,8 +521,8 @@ namespace Step64
 
     SolverControl solver_control(system_rhs_dev.size(),
                                  1e-12 * system_rhs_dev.l2_norm());
-    SolverCG<LinearAlgebra::distributed::Vector<double, MemorySpace::CUDA>> cg(
-      solver_control);
+    SolverCG<LinearAlgebra::distributed::Vector<double, MemorySpace::Default>>
+      cg(solver_control);
     cg.solve(*system_matrix_dev, solution_dev, system_rhs_dev, preconditioner);
 
     pcout << "  Solved in " << solver_control.last_step() << " iterations."
@@ -633,15 +637,6 @@ int main(int argc, char *argv[])
 
       Utilities::MPI::MPI_InitFinalize mpi_init(argc, argv, 1);
 
-      int         n_devices       = 0;
-      cudaError_t cuda_error_code = cudaGetDeviceCount(&n_devices);
-      AssertCuda(cuda_error_code);
-      const unsigned int my_mpi_id =
-        Utilities::MPI::this_mpi_process(MPI_COMM_WORLD);
-      const int device_id = my_mpi_id % n_devices;
-      cuda_error_code     = cudaSetDevice(device_id);
-      AssertCuda(cuda_error_code);
-
       HelmholtzProblem<3, 3> helmholtz_problem;
       helmholtz_problem.run();
     }
-- 
2.39.5