ICPSEP Content

122 串行部分 III

/*@
   MPE_Seq_end - Ends a sequential section of code.
   Input Parameters:
.  comm - Communicator to sequentialize.  
.  ng   - Number in group.  
@*/
void MPE_Seq_end( comm, ng )
MPI_Comm comm;
int      ng;
{
int        lidx, np, flag;
MPI_Status status;
MPI_Comm   local_comm;

MPI_Comm_rank( comm, &lidx );
MPI_Comm_size( comm, &np );
MPI_Attr_get( comm, MPE_Seq_keyval, (void *)&local_comm, &flag );
if (!flag) 
    MPI_Abort( comm, MPI_ERR_UNKNOWN );
/* Send to the first process in the next group OR to the first process
   in the processor set */
if ( (lidx % ng) == ng - 1 || lidx == np - 1) {
    MPI_Send( NULL, 0, MPI_INT, (lidx + 1) % np, 0, local_comm );
    }
if (lidx == 0) {
    MPI_Recv( NULL, 0, MPI_INT, np-1, 0, local_comm, &status );
    }
}