MPI + C 广播操作

int MPI_Bcast(void *buffer, int count, MPI_Datatype datatype, int root, MPI_Comm comm) 

阻塞式通信，广播时需要调用MPI_Bcast；

接收时也需要调用MPI_Bcast，并检查root参数和自身ID号是否相同，若不同则接收；

 

 

1、将主进程数组中的一个元素，广播，在其它进程数组的相应位置输出。

 

 

#include "mpi.h" #include <stdio.h> const int N = 10; int main (int argc, char *argv[]) { int i, rank, numprocs, master; int dp[N]; MPI_Init(&argc,&argv); MPI_Comm_rank(MPI_COMM_WORLD, &rank); MPI_Comm_size(MPI_COMM_WORLD, &numprocs); for (i = 0; i < N; i++) { dp[i] = rank; } //dp[rank] = rank; if(rank == master) MPI_Bcast(&dp[master], 1, MPI_INT, master, MPI_COMM_WORLD); MPI_Bcast(&dp[master], 1, MPI_INT, master, MPI_COMM_WORLD); if(rank==numprocs-1) { for (i = 0; i < N; i++) printf("%d ", dp[i]); printf("/n"); } MPI_Finalize(); return 0; } 

result:

[root@c0101 ~]# mpicxx bcast.cpp -o a [root@c0101 ~]# mpiexec -n 5 ./a 0 4 4 4 4 4 4 4 4 4 [root@c0101 ~]#  

 

 

 

2、从主进程读取一个数值，然后将其广播，并输出。

 

#include "mpi.h" #include <stdio.h> int main (int argc, char *argv[]) { int i, rank, numprocs, master; int value = -1; MPI_Init(&argc,&argv); MPI_Comm_rank(MPI_COMM_WORLD, &rank); MPI_Comm_size(MPI_COMM_WORLD, &numprocs); if(rank == master) { printf("please input a positive value:"); scanf("%d", &value); MPI_Bcast(&value, 1, MPI_INT, master, MPI_COMM_WORLD); } MPI_Bcast(&value, 1, MPI_INT, master, MPI_COMM_WORLD); MPI_Barrier(MPI_COMM_WORLD); printf("value of process %d is: %d/n", rank, value ); MPI_Finalize(); return 0; } 

result:

[root@c0101 ~]# mpicxx bcast.cpp -o a [root@c0101 ~]# mpiexec -n 5 ./a please input a positive value:8 value of process 2 is: 8 value of process 0 is: 8 value of process 3 is: 8 value of process 4 is: 8 value of process 1 is: 8 [root@c0101 ~]#  

 

 

另：如下会产生死锁,，其实完全可以用非阻塞通信MPI_Isend代替。

program main implicit none include 'mpif.h' integer,parameter::n = 10 integer myid, numprocs, ierr, i integer dp(0:10) call MPI_INIT(ierr) call MPI_COMM_RANK(MPI_COMM_WORLD, myid, ierr) call MPI_COMM_SIZE(MPI_COMM_WORLD, numprocs, ierr) do i = 0,n dp(i) = -1 enddo dp(myid) = myid call MPI_Barrier(MPI_COMM_WORLD,IERR) if(myid.ne.numprocs-1) call MPI_Bcast(dp(myid),1,MPI_INTEGER, & myid,MPI_COMM_WORLD,IERR) if(myid.eq.(numprocs-1)) then do i = 0, numprocs -2 call MPI_Bcast(dp(i),1,MPI_INTEGER,i, & MPI_COMM_WORLD,IERR) enddo print *,dp endif call MPI_FINALIZE(ierr) end