source: XIOS/dev/dev_trunk_omp/extern/src_ep_dev/ep_scatter.cpp @ 1646

#ifdef _usingEP
/*!
   \file ep_gather.cpp
   \since 2 may 2016

   \brief Definitions of MPI collective function: MPI_Scatter
 */

#include "ep_lib.hpp"
#include <mpi.h>
#include "ep_declaration.hpp"
#include "ep_mpi.hpp"

using namespace std;

namespace ep_lib
{

  int MPI_Scatter_local(void *sendbuf, int sendcount, MPI_Datatype sendtype, void *recvbuf, int recvcount, MPI_Datatype recvtype, int local_root, MPI_Comm comm)
  {
    assert(valid_type(sendtype) && valid_type(recvtype));
    assert(recvcount == sendcount);

    ::MPI_Aint datasize, lb;
    ::MPI_Type_get_extent(to_mpi_type(sendtype), &lb, &datasize);

    int ep_rank_loc = comm->ep_comm_ptr->size_rank_info[1].first;
    int num_ep = comm->ep_comm_ptr->size_rank_info[1].second;


    if(ep_rank_loc == local_root)
      comm->my_buffer->void_buffer[local_root] = const_cast<void*>(sendbuf);

    MPI_Barrier_local(comm);

    #pragma omp critical (_scatter)      
    memcpy(recvbuf, comm->my_buffer->void_buffer[local_root]+datasize*ep_rank_loc*sendcount, datasize * recvcount);
    

    MPI_Barrier_local(comm);
  }

  int MPI_Scatter(const void *sendbuf, int sendcount, MPI_Datatype sendtype, void *recvbuf, int recvcount, MPI_Datatype recvtype, int root, MPI_Comm comm)
  {
    if(!comm->is_ep) return ::MPI_Scatter(sendbuf, sendcount, to_mpi_type(sendtype), recvbuf, recvcount, to_mpi_type(recvtype), root, to_mpi_comm(comm->mpi_comm));
    if(comm->is_intercomm) return MPI_Scatter_intercomm(sendbuf, sendcount, sendtype, recvbuf, recvcount, recvtype, root, comm);
   
    assert(sendcount == recvcount);

    int ep_rank = comm->ep_comm_ptr->size_rank_info[0].first;
    int ep_rank_loc = comm->ep_comm_ptr->size_rank_info[1].first;
    int mpi_rank = comm->ep_comm_ptr->size_rank_info[2].first;
    int ep_size = comm->ep_comm_ptr->size_rank_info[0].second;
    int num_ep = comm->ep_comm_ptr->size_rank_info[1].second;
    int mpi_size = comm->ep_comm_ptr->size_rank_info[2].second;

    int root_mpi_rank = comm->ep_rank_map->at(root).second;
    int root_ep_loc = comm->ep_rank_map->at(root).first;

    bool is_master = (ep_rank_loc==0 && mpi_rank != root_mpi_rank ) || ep_rank == root;
    bool is_root = ep_rank == root;

    MPI_Datatype datatype = sendtype;
    int count = sendcount;

    ::MPI_Aint datasize, lb;
    ::MPI_Type_get_extent(to_mpi_type(datatype), &lb, &datasize);
    
    void *tmp_sendbuf;
    if(is_root) tmp_sendbuf = new void*[ep_size * count * datasize];

    // reorder tmp_sendbuf
    std::vector<int>local_ranks(num_ep);
    std::vector<int>ranks(ep_size);

    if(mpi_rank == root_mpi_rank) MPI_Gather_local(&ep_rank, 1, MPI_INT, local_ranks.data(), root_ep_loc, comm);
    else                          MPI_Gather_local(&ep_rank, 1, MPI_INT, local_ranks.data(), 0, comm);


    std::vector<int> recvcounts(mpi_size, 0);
    std::vector<int> displs(mpi_size, 0);


    if(is_master)
    {
      for(int i=0; i<ep_size; i++)
      {
        recvcounts[comm->ep_rank_map->at(i).second]++;
      }

      for(int i=1; i<mpi_size; i++)
        displs[i] = displs[i-1] + recvcounts[i-1];

      ::MPI_Gatherv(local_ranks.data(), num_ep, to_mpi_type(MPI_INT), ranks.data(), recvcounts.data(), displs.data(), to_mpi_type(MPI_INT), root_mpi_rank, to_mpi_comm(comm->mpi_comm));
    }


    if(is_root)
    for(int i=0; i<ep_size; i++)
    {
      memcpy(tmp_sendbuf + i*datasize*count, sendbuf + ranks[i]*datasize*count, count*datasize);
    }

    // MPI_Scatterv from root to masters
    void* local_recvbuf;
    if(is_master) local_recvbuf = new void*[datasize * num_ep * count];


    if(is_master)
    {
      int local_sendcount = num_ep * count;
      ::MPI_Gather(&local_sendcount, 1, to_mpi_type(MPI_INT), recvcounts.data(), 1, to_mpi_type(MPI_INT), root_mpi_rank, to_mpi_comm(comm->mpi_comm));
      
      if(is_root) for(int i=1; i<mpi_size; i++) displs[i] = displs[i-1] + recvcounts[i-1];

      ::MPI_Scatterv(tmp_sendbuf, recvcounts.data(), displs.data(), to_mpi_type(sendtype), local_recvbuf, num_ep*count, to_mpi_type(recvtype), root_mpi_rank, to_mpi_comm(comm->mpi_comm));

    }

    if(mpi_rank == root_mpi_rank) MPI_Scatter_local(local_recvbuf, count, sendtype, recvbuf, recvcount, recvtype, root_ep_loc, comm);
    else                          MPI_Scatter_local(local_recvbuf, count, sendtype, recvbuf, recvcount, recvtype, 0, comm);

    if(is_root)   delete[] tmp_sendbuf;
    if(is_master) delete[] local_recvbuf;
  }


  int MPI_Scatter_intercomm(const void *sendbuf, int sendcount, MPI_Datatype sendtype, void *recvbuf, int recvcount, MPI_Datatype recvtype, int root, MPI_Comm comm)
  {
    printf("MPI_Scatter_intercomm not yet implemented\n");
    MPI_Abort(comm, 0);
  }

}
#endif