tests: Test that MPI can access view data

Signed-off-by: Carl Pearson <cwpears@sandia.gov>

unit_tests/CMakeLists.txt

@@ -70,6 +70,7 @@ if(KOKKOSCOMM_ENABLE_MPI)
     COMMAND
       ${MPIEXEC_EXECUTABLE} ${MPIEXEC_NUMPROC_FLAG} 2 ./test-mpi
   )
+
 endif()
 
 # Tests using the MPI communication space, but not linking with MPI itself
@@ -78,8 +79,9 @@ target_sources(
   test-main
   PRIVATE
     test_main.cpp
-    mpi/test_gtest_mpi.cpp
-    mpi/test_sendrecv.cpp
+    mpi/test_gtest_mpi.cpp        # make sure gtest is working
+    mpi/test_mpi_view_access.cpp  # make sure MPI can access Kokkos::View data
+    mpi/test_sendrecv.cpp         # other tests...
     mpi/test_allgather.cpp
     mpi/test_alltoall.cpp
     mpi/test_isendrecv.cpp

unit_tests/mpi/test_mpi_view_access.cpp

@@ -0,0 +1,64 @@
+//@HEADER
+// ************************************************************************
+//
+//                        Kokkos v. 4.0
+//       Copyright (2022) National Technology & Engineering
+//               Solutions of Sandia, LLC (NTESS).
+//
+// Under the terms of Contract DE-NA0003525 with NTESS,
+// the U.S. Government retains certain rights in this software.
+//
+// Part of Kokkos, under the Apache License v2.0 with LLVM Exceptions.
+// See https://kokkos.org/LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//@HEADER
+
+#include <iostream>
+
+#include <gtest/gtest.h>
+
+#include "KokkosComm/KokkosComm.hpp"
+
+namespace {
+
+using namespace KokkosComm::mpi;
+
+namespace {
+void doit() {
+  int rank, size;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  MPI_Comm_size(MPI_COMM_WORLD, &size);
+  if (size < 2) {
+    GTEST_SKIP() << "requires at least 2 ranks";
+  }
+
+  const int n = 1024 * 1024;
+  Kokkos::View<double *> a("a", n);
+
+  if (0 == rank) {
+    Kokkos::parallel_for(
+        n, KOKKOS_LAMBDA(const int i) { a(i) = i; });
+    Kokkos::fence();
+
+    std::cerr << "sending buffer is" << a.data() << "-" << a.data() + n << "\n";
+    MPI_Send(a.data(), n, MPI_DOUBLE, 1, 0, MPI_COMM_WORLD);
+  } else if (1 == rank) {
+    std::cerr << "recving buffer is" << a.data() << "-" << a.data() + n << "\n";
+    MPI_Recv(a.data(), n, MPI_DOUBLE, 0, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
+  }
+
+  auto a_h = Kokkos::create_mirror_view_and_copy(Kokkos::DefaultExecutionSpace{}, a);
+  Kokkos::fence();
+
+  for (int i = 0; i < n; ++i) {
+    if (a_h[i] != i) {
+      ASSERT_EQ(a_h[i], i);
+    }
+  }
+}
+}  // namespace
+
+TEST(MpiViewAccess, Basic) { doit(); }
+
+}  // namespace