2:  #include <petscsys.h>

  4: /*
  5:     Allows sending/receiving larger messages then 2 gigabytes in a single call
  6: */

  8: PetscErrorCode MPIULong_Send(void *mess,PetscInt cnt, MPI_Datatype type,PetscMPIInt to, PetscMPIInt tag, MPI_Comm comm)
  9: {
 10:   PetscErrorCode  ierr;
 11:   static PetscInt CHUNKSIZE = 250000000; /* 250,000,000 */
 12:   PetscInt        i,numchunks;
 13:   PetscMPIInt     icnt;

 16:   numchunks = cnt/CHUNKSIZE + 1;
 17:   for (i=0; i<numchunks; i++) {
 18:     PetscMPIIntCast((i < numchunks-1) ? CHUNKSIZE : cnt - (numchunks-1)*CHUNKSIZE,&icnt);
 19:     MPI_Send(mess,icnt,type,to,tag,comm);
 20:     if (type == MPIU_INT)         mess = (void*) (((PetscInt*)mess) + CHUNKSIZE);
 21:     else if (type == MPIU_SCALAR) mess = (void*) (((PetscScalar*)mess) + CHUNKSIZE);
 22:     else SETERRQ(comm,PETSC_ERR_SUP,"No support for this datatype");
 23:   }
 24:   return(0);
 25: }

 27: PetscErrorCode MPIULong_Recv(void *mess,PetscInt cnt, MPI_Datatype type,PetscMPIInt from, PetscMPIInt tag, MPI_Comm comm)
 28: {
 29:   int             ierr;
 30:   static PetscInt CHUNKSIZE = 250000000; /* 250,000,000 */
 31:   MPI_Status      status;
 32:   PetscInt        i,numchunks;
 33:   PetscMPIInt     icnt;

 36:   numchunks = cnt/CHUNKSIZE + 1;
 37:   for (i=0; i<numchunks; i++) {
 38:     PetscMPIIntCast((i < numchunks-1) ? CHUNKSIZE : cnt - (numchunks-1)*CHUNKSIZE,&icnt);
 39:     MPI_Recv(mess,icnt,type,from,tag,comm,&status);
 40:     if (type == MPIU_INT)         mess = (void*) (((PetscInt*)mess) + CHUNKSIZE);
 41:     else if (type == MPIU_SCALAR) mess = (void*) (((PetscScalar*)mess) + CHUNKSIZE);
 42:     else SETERRQ(comm,PETSC_ERR_SUP,"No support for this datatype");
 43:   }
 44:   return(0);
 45: }