Derandomize CUDA devices used in test

diff --git a/tests/tests.h b/tests/tests.h
index 2c27ab7d32f538ee1a5664a019d9e5423424f0b9..d798e0236ef5501af82e968a11984f4a180fd382 100644 (file)
--- a/tests/tests.h
+++ b/tests/tests.h
@@ -593,10 +593,12 @@ struct MPILogInitAll
 
 
 #ifdef DEAL_II_COMPILER_CUDA_AWARE
-// By default, all the ranks will try to access the device 0. We can distribute
-// the load better by using a random device which is done in this function. In
-// case tests use MPI, we make sure to set subsequent devices. MPI needs to be
-// initialized before using this function.
+// By default, all the ranks will try to access the device 0.
+// If we are running with MPI support it is better to address different graphic
+// cards for different processes even if only one node is used. The choice below
+// is based on the MPI proccess id.
+// MPI needs to be initialized before using this function.
+//
 // Also initialize a dummy handle that makes sure that unused memory is released
 // before the device shuts down.
 void
@@ -613,18 +615,38 @@ init_cuda(const bool use_mpi = false)
   int         n_devices       = 0;
   cudaError_t cuda_error_code = cudaGetDeviceCount(&n_devices);
   AssertCuda(cuda_error_code);
-  if (my_id == 0)
-    {
-      Testing::srand(std::time(nullptr));
-      device_id = Testing::rand() % n_devices;
-    }
-#  ifdef DEAL_II_WITH_MPI
-  if (use_mpi)
-    MPI_Bcast(&device_id, 1, MPI_INT, 0, MPI_COMM_WORLD);
-#  endif
-  device_id       = (device_id + my_id) % n_devices;
-  cuda_error_code = cudaSetDevice(device_id);
+  const int device_id = my_id % n_devices;
+  cuda_error_code     = cudaSetDevice(device_id);
   AssertCuda(cuda_error_code);
+
+  // In principle, we should be able to distribute the load better by
+  // choosing a random graphics card. For some reason, this produces timeouts
+  // on the tester we use mainly for the CUDA tests so we don't use the
+  // following optimization by default.
+
+  /*
+  # ifndef DEAL_II_WITH_MPI
+    Assert(use_mpi == false, ExcInternalError());
+  #  endif
+    const unsigned int my_id =
+      use_mpi ? Utilities::MPI::this_mpi_process(MPI_COMM_WORLD) : 0;
+    int         device_id       = 0;
+    int         n_devices       = 0;
+    cudaError_t cuda_error_code = cudaGetDeviceCount(&n_devices);
+    AssertCuda(cuda_error_code);
+    if (my_id == 0)
+      {
+        Testing::srand(std::time(nullptr));
+        device_id = Testing::rand() % n_devices;
+      }
+  #  ifdef DEAL_II_WITH_MPI
+    if (use_mpi)
+      MPI_Bcast(&device_id, 1, MPI_INT, 0, MPI_COMM_WORLD);
+  #  endif
+    device_id       = (device_id + my_id) % n_devices;
+    cuda_error_code = cudaSetDevice(device_id);
+    AssertCuda(cuda_error_code);
+  */
 }
 #endif