template<typename MA, typename MB>
typename std::enable_if<
hpc::matvec::IsGeMatrix<MA>::value && hpc::matvec::IsGeMatrix<MB>::value &&
std::is_same<typename MA::ElementType, typename MB::ElementType>::value,
int>::type
scatter_by_row(const MA& A, MB& B, int root, MPI_Comm comm) {
assert(A.numCols == B.numCols);
int nof_processes; MPI_Comm_size(comm, &nof_processes);
int rank; MPI_Comm_rank(comm, &rank);
hpc::aux::Slices<int> slices(nof_processes, A.numRows);
std::vector<int> counts(nof_processes);
std::vector<int> offsets(nof_processes);
MPI_Datatype rowtype_A = get_row_type(A);
for (int i = 0; i < nof_processes; ++i) {
if (i < A.numRows) {
counts[i] = slices.size(i);
offsets[i] = slices.offset(i);
} else {
counts[i] = 0; offsets[i] = 0;
}
}
int recvcount = counts[rank];
assert(B.numRows == recvcount);
MPI_Datatype rowtype_B = get_row_type(B);
/* OpenMPI implementation of Debian wheezy expects void* instead
of const void*; hence we need to remove const */
return MPI_Scatterv((void*) &A(0, 0), &counts[0], &offsets[0], rowtype_A,
&B(0, 0), recvcount, rowtype_B, root, comm);
}
template<typename MA, typename MB>
typename std::enable_if<
hpc::matvec::IsGeMatrix<MA>::value && hpc::matvec::IsGeMatrix<MB>::value &&
std::is_same<typename MA::ElementType, typename MB::ElementType>::value,
int>::type
gather_by_row(const MA& A, MB& B, int root, MPI_Comm comm) {
assert(A.numCols == B.numCols);
int nof_processes; MPI_Comm_size(comm, &nof_processes);
int rank; MPI_Comm_rank(comm, &rank);
hpc::aux::Slices<int> slices(nof_processes, B.numRows);
std::vector<int> counts(nof_processes);
std::vector<int> offsets(nof_processes);
for (int i = 0; i < nof_processes; ++i) {
if (i < B.numRows) {
counts[i] = slices.size(i);
offsets[i] = slices.offset(i);
} else {
counts[i] = 0; offsets[i] = 0;
}
}
int sendcount = counts[rank];
assert(A.numRows == sendcount);
MPI_Datatype rowtype_A = get_row_type(A);
MPI_Datatype rowtype_B = get_row_type(B);
/* OpenMPI implementation of Debian wheezy expects void* instead
of const void*; hence we need to remove const */
return MPI_Gatherv((void*) &A(0, 0), sendcount, rowtype_A,
&B(0, 0), &counts[0], &offsets[0], rowtype_B, root, comm);
}