Question

我有一个小型方案。

#include "mpi.h"
#include <stdio.h>

int main(int argc, char *argv[])
{
int rank, size;
int buf;
int err;
MPI_Status status;

err = MPI_Init(&argc, &argv);
if(err == MPI_SUCCESS) {
MPI_Comm_size(MPI_COMM_WORLD, &size);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);

if(rank == 0) {
printf("Buffer size is less than 10
");
printf("进入缓冲地带: ");
scanf("%d", &buf);
MPI_Send(&buf, 1, MPI_INT, 1, 10,
MPI_COMM_WORLD);
}
else {
MPI_Recv(&buf, 1, MPI_INT, 0, 10,
MPI_COMM_WORLD, &status);
}
printf("process[%d]: buffer size : %d
", rank,buf);

}
err = MPI_Finalize();
return 0;
}

产出如下:

[veda@home-pc hpc]$ mpicc test.c
[veda@home-pc hpc]$ mpiexec -np 2 a.out
Buffer size is less than 10
3
进入缓冲地带: process[0]: buffer size : 3
process[1]: buffer size : 3

在这一产出中,你可以注意到:

进入缓冲地带:

在我进入缓冲地带后,正在印刷/投稿。

人人都能告诉我如何解决这一问题。

Answer 1

I suspect your standard output is line-buffered. The "Enter the buffer size: " is not printed until "process[%d]: buffer size : %d " (containing a newline) is printed. The solution is to explicitly flush the standard output between the printf and the scanf:

printf("Enter the buffer size: ");
fflush(stdout);
scanf("%d", &buf);

Answer 2

您可以使用:

puts("Enter the buffer size:");
gets(buf);

Answer 3

If you are using Eclipse for parallel programming, then (most probably) that is what causes the issue.
It is some kind of glitch in PTP. You can also experience this with printf, it only prints after your program has finished execution or was shut down (not while the program is running).
Then try running your code from the command line, it will work.

Else (If it still gets hanged or gives weird behaviour) then try calling
fflush(stdout) or while ((c = getchar()) != && c != EOF);
to flush everything before reading user input.

Answer 4

确实,你拥有的东西。

printf("Buffer size is less than 10
");
printf("Enter the buffer size: ");

我指的是你怀疑它会做些什么? 查阅:if(rank=0),看我的含义。事实上,你甚至没有使用你使用10 %的人。

也许希望:

if(rank == 0) {
   printf("Enter the buffer size: ");
   scanf("%d", &buf);
   printf("Buffer size is less than %d
", buf);
   //...

友情链接