mpicomm.c

#include <mpi.h>
#include <stdlib.h>
#include <stdio.h>

#include "mpicomm.h"
#include "mpitypes.h"
#include "mesh.h"

#if MPI_VERSION < 3
#pragma message("MPI_Version < 3 => Sparse collectives are not supported.")
#endif

// --------------------------------------------- Helper function declarations


// ==========================================================================

void mpi_broadcast_configuration_start(conf_t *configuration, MPI_Request *request)
{
   MPI_Datatype conf_mpitype;
   mpitype_conf_init(&conf_mpitype);

#if MPI_VERSION >= 3
   MPI_Ibcast(configuration, 1, conf_mpitype, 0, MPI_COMM_WORLD, request);
#else
   MPI_Bcast(configuration, 1, conf_mpitype, 0, MPI_COMM_WORLD);
   *request = MPI_REQUEST_NULL;
#endif

   mpitype_conf_free(&conf_mpitype);
}

void mpi_broadcast_configuration_finish(MPI_Request *request)
{
   // Note for case MPI_VERSION < 3:
   // Calling MPI_Wait with MPI_REQUEST_NULL is safe and will return immediately.
   MPI_Wait(request, MPI_STATUS_IGNORE);
}

void mpi_broadcast_decomposition(box_t *decomposition)
{
   int nprocs;
   MPI_Datatype box_mpitype;

   MPI_Comm_size(MPI_COMM_WORLD, &nprocs);
   mpitype_box_init(&box_mpitype);
   MPI_Bcast(decomposition, nprocs, box_mpitype, 0, MPI_COMM_WORLD);

   mpitype_box_free(&box_mpitype);
}

void mpi_create_graph_communicator(const mesh_t *mesh, const conf_t *configuration, MPI_Comm *graph_comm)
{
   int n_neighbors = mesh->n_neighbors;
   int *buffer = malloc(3 * n_neighbors * sizeof(*buffer));
   int *neighbor_ranks = buffer + 0 * n_neighbors;
   int *recv_weights = buffer + 1 * n_neighbors;
   int *send_weights = buffer + 2 * n_neighbors;
   const neighbor_info *nb;
   int allow_reorder = 1;
   int i;

   for(i = 0; i < n_neighbors; i++) {
      nb = &mesh->neighbors[i];
      neighbor_ranks[i] = nb->mpi_rank;
      recv_weights[i] = nb->halo_incoming.domain.volume;
      send_weights[i] = nb->halo_outgoing.domain.volume;
   }

   MPI_Dist_graph_create_adjacent(
         MPI_COMM_WORLD,
         n_neighbors, neighbor_ranks, recv_weights,
         n_neighbors, neighbor_ranks, send_weights,
         MPI_INFO_NULL, allow_reorder,
         graph_comm);

   free(buffer);
}

void mpi_halo_exchange_int_sparse_collective(int_field_t *field)
{
#if MPI_VERSION >= 3
   const mesh_t *mesh = field->mesh;
   int *data = field->data;
   int n_neighbors = mesh->n_neighbors;
   int i;

   int *counts = malloc(n_neighbors * sizeof(*counts));
   MPI_Aint *displs = malloc(n_neighbors * sizeof(*displs));

   MPI_Datatype *types = malloc(2 * n_neighbors * sizeof(*types));
   MPI_Datatype *send_types = types + 0 * n_neighbors;
   MPI_Datatype *recv_types = types + 1 * n_neighbors;

   for(i = 0; i < n_neighbors; i++) {
      counts[i] = 1;
      displs[i] = 0;
      send_types[i] = mesh->neighbors[i].halo_outgoing.transfer_type_int;
      recv_types[i] = mesh->neighbors[i].halo_incoming.transfer_type_int;
   }

   MPI_Neighbor_alltoallw(
         data, counts, displs, send_types,
         data, counts, displs, recv_types,
         mesh->communicator
   );

   free(counts);
   free(displs);
   free(types);
#else
   fprintf(stderr, "Your MPI implementation does not support sparse collective operations.\n");
   MPI_Abort(MPI_COMM_WORLD, EXIT_FAILURE);
#endif
}

void mpi_halo_exchange_int_collective(int_field_t *field)
{
   const mesh_t *mesh = field->mesh;
   int *data = field->data;
   int n_neighbors = mesh->n_neighbors;
   int nprocs, i, nb_rank;

   MPI_Comm_size(mesh->communicator, &nprocs);

   int *counts = malloc(nprocs * sizeof(*counts));
   int *displs = malloc(nprocs * sizeof(*displs));

   MPI_Datatype *types = malloc(2 * nprocs * sizeof(*types));
   MPI_Datatype *send_types = types + 0 * nprocs;
   MPI_Datatype *recv_types = types + 1 * nprocs;

   for(i = 0; i < nprocs; i++) {
      counts[i] = 0;
      displs[i] = 0;
      send_types[i] = MPI_BYTE;
      recv_types[i] = MPI_BYTE;
   }

   for(i = 0; i < n_neighbors; i++) {
      nb_rank = mesh->neighbors[i].mpi_rank;
      counts[nb_rank] = 1;
      displs[nb_rank] = 0;
      send_types[nb_rank] = mesh->neighbors[i].halo_outgoing.transfer_type_int;
      recv_types[nb_rank] = mesh->neighbors[i].halo_incoming.transfer_type_int;
   }

   MPI_Alltoallw(
         data, counts, displs, send_types,
         data, counts, displs, recv_types,
         mesh->communicator
   );

   free(counts);
   free(displs);
   free(types);
}

void mpi_halo_exchange_int_p2p_default(int_field_t *field)
{
   const mesh_t *mesh = field->mesh;
   int *data = field->data;
   int n_neighbors = mesh->n_neighbors;
   int i, tag = 0;
   neighbor_info *nb;

   MPI_Request *requests = malloc(2 * n_neighbors * sizeof(*requests));
   MPI_Request *recv_requests = requests + 1 * n_neighbors;
   MPI_Request *send_requests = requests + 0 * n_neighbors;

   // Post non-blocking receives for all neighbors
   for(i = 0; i < n_neighbors; i++) {
      nb = &mesh->neighbors[i];
      MPI_Irecv(
            data, 1, nb->halo_incoming.transfer_type_int, nb->mpi_rank, tag, 
            mesh->communicator, &recv_requests[i]
      );
   }
  
   // Post non-blocking sends for all neighbors
   for(i = 0; i < n_neighbors; i++) {
      nb = &mesh->neighbors[i];
      MPI_Isend(
            data, 1, nb->halo_outgoing.transfer_type_int, nb->mpi_rank, tag,
            mesh->communicator, &send_requests[i]
      ); 
   }

   // Finish operations
   MPI_Waitall(2 * n_neighbors, requests, MPI_STATUSES_IGNORE);
   free(requests);
}

void mpi_halo_exchange_int_p2p_synchronous(int_field_t *field)
{
   const mesh_t *mesh = field->mesh;
   int *data = field->data;
   int n_neighbors = mesh->n_neighbors;
   int i, tag = 0;
   neighbor_info *nb;

   MPI_Request *requests = malloc(2 * n_neighbors * sizeof(*requests));
   MPI_Request *recv_requests = requests + 1 * n_neighbors;
   MPI_Request *send_requests = requests + 0 * n_neighbors;

   // Post non-blocking receives for all neighbors
   for(i = 0; i < n_neighbors; i++) {
      nb = &mesh->neighbors[i];
      MPI_Irecv(
            data, 1, nb->halo_incoming.transfer_type_int, nb->mpi_rank, tag, 
            mesh->communicator, &recv_requests[i]
      );
   }
  
   // Post non-blocking synchronous sends for all neighbors
   for(i = 0; i < n_neighbors; i++) {
      nb = &mesh->neighbors[i];
      MPI_Issend(
            data, 1, nb->halo_outgoing.transfer_type_int, nb->mpi_rank, tag,
            mesh->communicator, &send_requests[i]
      ); 
   }

   // Finish operations
   MPI_Waitall(2 * n_neighbors, requests, MPI_STATUSES_IGNORE);
   free(requests);
}

void mpi_halo_exchange_int_p2p_ready(int_field_t *field)
{
   const mesh_t *mesh = field->mesh;
   int *data = field->data;
   int n_neighbors = mesh->n_neighbors;
   int i, tag = 0;
   neighbor_info *nb;

   MPI_Request *requests = malloc(2 * n_neighbors * sizeof(*requests));
   MPI_Request *recv_requests = requests + 1 * n_neighbors;
   MPI_Request *send_requests = requests + 0 * n_neighbors;

   // Post non-blocking receives for all neighbors
   for(i = 0; i < n_neighbors; i++) {
      nb = &mesh->neighbors[i];
      MPI_Irecv(
            data, 1, nb->halo_incoming.transfer_type_int, nb->mpi_rank, tag, 
            mesh->communicator, &recv_requests[i]
      );
   }

   // Be sure that all receives for current communication round have been posted
   MPI_Barrier(mesh->communicator);
  
   // Post non-blocking ready sends for all neighbors
   for(i = 0; i < n_neighbors; i++) {
      nb = &mesh->neighbors[i];
      MPI_Irsend(
            data, 1, nb->halo_outgoing.transfer_type_int, nb->mpi_rank, tag,
            mesh->communicator, &send_requests[i]
      ); 
   }

   // Finish operations
   MPI_Waitall(2 * n_neighbors, requests, MPI_STATUSES_IGNORE);
   free(requests);
}

// --------------------------------------------------------- Helper functions