gather_all.h

#ifndef LINEARALGEBRA_SRC_MOLPRO_LINALG_ARRAY_UTIL_GATHER_ALL_H
#define LINEARALGEBRA_SRC_MOLPRO_LINALG_ARRAY_UTIL_GATHER_ALL_H
#include <molpro/linalg/array/util/Distribution.h>
#include <mpi.h>
#include <vector>
 
namespace molpro::linalg::array::util {
 
inline void gather_all(const Distribution<size_t>& distr, MPI_Comm commun, double* first_elem) {
  int nproc, mpi_rank;
  MPI_Comm_size(commun, &nproc);
  MPI_Comm_rank(commun, &mpi_rank);
  std::vector<int> chunks(nproc), displs(nproc);
  for (int i = 0; i < nproc; i++) {
    displs[i] = distr.range(i).first;
    chunks[i] = distr.range(i).second - distr.range(i).first;
  }
  MPI_Allgatherv(MPI_IN_PLACE, 0, MPI_DATATYPE_NULL, first_elem, chunks.data(), displs.data(), MPI_DOUBLE, commun);
}
 
} // namespace molpro::linalg::array::util
 
#endif // LINEARALGEBRA_SRC_MOLPRO_LINALG_ARRAY_UTIL_GATHER_ALL_H