Function main

modules/mpi/tutorials/ospMPIDistributedExamples.cpp:34–150

vec3i computeGrid(int num);

int main(int argc, char **argv)
{
  int mpiThreadCapability = 0;
  MPI_Init_thread(&argc, &argv, MPI_THREAD_MULTIPLE, &mpiThreadCapability);
  if (mpiThreadCapability != MPI_THREAD_MULTIPLE
      && mpiThreadCapability != MPI_THREAD_SERIALIZED) {
    fprintf(stderr,
        "OSPRay requires the MPI runtime to support thread "
        "multiple or thread serialized.\n");
    return 1;
  }

  std::string sceneName = "gravity_spheres_volume";
  if (argc == 2) {
    sceneName = argv[1];
  }

  int mpiRank = 0;
  int mpiWorldSize = 0;
  MPI_Comm_rank(MPI_COMM_WORLD, &mpiRank);
  MPI_Comm_size(MPI_COMM_WORLD, &mpiWorldSize);

  std::cout << "OSPRay rank " << mpiRank << "/" << mpiWorldSize << "\n";

  // load the MPI module, and select the MPI distributed device. Here we
  // do not call ospInit, as we want to explicitly pick the distributed
  // device
  auto OSPRAY_MPI_DISTRIBUTED_GPU =
      utility::getEnvVar<int>("OSPRAY_MPI_DISTRIBUTED_GPU").value_or(0);
  if (OSPRAY_MPI_DISTRIBUTED_GPU) {
    ospLoadModule("mpi_distributed_gpu");
  } else {
    ospLoadModule("mpi_distributed_cpu");
  }

  {
    cpp::Device mpiDevice("mpiDistributed");
    mpiDevice.commit();
    mpiDevice.setCurrent();

    // set an error callback to catch any OSPRay errors and exit the application
    mpiDevice.setErrorCallback(
        [](void *, OSPError error, const char *errorDetails) {
          std::cerr << "OSPRay error: " << errorDetails << std::endl;
          exit(error);
        });

    // Regions are assigned to ranks in 3D grid, determine which brick of the
    // grid is owned by this rank
    const vec3i distribGrid = computeGrid(mpiWorldSize);
    const vec3i distribBrickId(mpiRank % distribGrid.x,
        (mpiRank / distribGrid.x) % distribGrid.y,
        mpiRank / (distribGrid.x * distribGrid.y));

    std::cout << "scene = " << sceneName << "\n";
    auto builder = testing::newBuilder(sceneName);
    testing::setParam(builder, "rendererType", "scivis");
    testing::commit(builder);