source: issm/trunk/src/c/toolkits/mpi/patches/GetOwnershipBoundariesFromRange.cpp@ 15396

/*! \file:  GetOwnershipBoundariesFromRange.cpp
 *  \brief from a local range on each cpu, we determine what 
 *  lower row and upper row from a matrix a cpu owns.
 */

#ifdef HAVE_CONFIG_H
        #include <config.h>
#else
#error "Cannot compile with HAVE_CONFIG_H symbol! run configure first!"
#endif

#include <stdio.h>
#include "../../../shared/MemOps/MemOps.h"
#include "../../../shared/io/Comm/Comm.h"

void GetOwnershipBoundariesFromRange(int* plower_row,int* pupper_row,int range,COMM comm){

        /*externals :*/
        int my_rank;
        int num_procs;

        /*recover my_rank and num_procs:*/
        MPI_Comm_size(comm,&num_procs);
        MPI_Comm_rank(comm,&my_rank);

        /*output: */
        int lower_row,upper_row;

        /*Gather all range values into allranges, for all nodes*/
        int* allranges=xNew<int>(num_procs);
        MPI_Allgather(&range,1,MPI_INT,allranges,1,MPI_INT,comm);

        /*From all ranges, get lower row and upper row*/
        lower_row=0;
        upper_row=lower_row+allranges[0];
        for(int i=1;i<=my_rank;i++){
                lower_row=lower_row+allranges[i-1];
                upper_row=upper_row+allranges[i];
        }

        /*Assign output*/
        *plower_row=lower_row;
        *pupper_row=upper_row;
        xDelete<int>(allranges);
}