MPI_INIT() and MPI_FINALIZE can only be called once per program, as your error hints at. This old answer from half a year ago sketches how to get MPI to run some parts of your program in parallel: int main(int argc, char *argv[]) { MPI_Init(&argc, &argv); MPI_Comm_size(MPI_COMM_WORLD,&numprocs); MPI_Comm_rank(MPI_COMM_WORLD,&myid); if (myid == 0) { // Do the … Read more
The only authoritative source, the MPI standard, defines MPI_FLOAT_INT as (Section 5.9.4 MINLOC and MAXLOC): The datatype MPI_FLOAT_INT is as if defined by the following sequence of instructions. type[0] = MPI_FLOAT type[1] = MPI_INT disp[0] = 0 disp[1] = sizeof(float) block[0] = 1 block[1] = 1 MPI_TYPE_CREATE_STRUCT(2, block, disp, type, MPI_FLOAT_INT) Similar statements apply for … Read more
You must tell the compiler about the MPI stuff (mainly variables). The modern way is introducing use mpi in every scope. In the old days it was also done using include “mpif.h” but that has several disadvantages. Namely, because it is compatible with FORTRAN 77, it does not introduce explicit interfaces for any MPI subroutines … Read more