【发布时间】:2026-02-02 22:15:02
【问题描述】:
我对 MPI 函数进行了一些测试,以了解它是如何工作的,并且使用 MPI_Barrier 得到了一个奇怪的结果:如果我在类似代码中使用它,它会达到每个人的预期
int main(int argc, char *argv[])
{
<some code>
MPI_Barrier(MPI_COMM_WORLD);
<more code>
MPI_Barrier(MPI_COMM_WORLD);
<...>
}
但是当我从循环内部调用它时,我会得到随机结果。具体来说,我有以下测试代码:
#include "mpi.h"
#include <stdio.h>
int main(int argc, char *argv[])
{
int i, rb, rank, nprocs;
MPI_Init(&argc,&argv);
MPI_Comm_size(MPI_COMM_WORLD,&nprocs);
MPI_Comm_rank(MPI_COMM_WORLD,&rank);
i=0;
while(i<5)
{
rb=MPI_Barrier(MPI_COMM_WORLD);
printf("Itartion %d. I am %d of %d. MPIBarrierRes: %d\n", i, rank, nprocs, rb);
i++;
}
MPI_Finalize();
return 0;
}
当我用 3 个任务运行它时,我随机得到:
Itartion 0. I am 0 of 3. MPIBarrierRes: 0
Itartion 0. I am 2 of 3. MPIBarrierRes: 0
Itartion 0. I am 1 of 3. MPIBarrierRes: 0
Itartion 1. I am 0 of 3. MPIBarrierRes: 0
Itartion 1. I am 1 of 3. MPIBarrierRes: 0
Itartion 1. I am 2 of 3. MPIBarrierRes: 0
Itartion 2. I am 0 of 3. MPIBarrierRes: 0
Itartion 2. I am 1 of 3. MPIBarrierRes: 0
Itartion 2. I am 2 of 3. MPIBarrierRes: 0
Itartion 3. I am 0 of 3. MPIBarrierRes: 0
Itartion 3. I am 1 of 3. MPIBarrierRes: 0
Itartion 3. I am 2 of 3. MPIBarrierRes: 0
Itartion 4. I am 0 of 3. MPIBarrierRes: 0
Itartion 4. I am 1 of 3. MPIBarrierRes: 0
Itartion 4. I am 2 of 3. MPIBarrierRes: 0
这是我所期望的,或者只是相反:
Itartion 0. I am 2 of 3. MPIBarrierRes: 0
Itartion 1. I am 2 of 3. MPIBarrierRes: 0
Itartion 2. I am 2 of 3. MPIBarrierRes: 0
Itartion 3. I am 2 of 3. MPIBarrierRes: 0
Itartion 4. I am 2 of 3. MPIBarrierRes: 0
Itartion 0. I am 0 of 3. MPIBarrierRes: 0
Itartion 1. I am 0 of 3. MPIBarrierRes: 0
Itartion 2. I am 0 of 3. MPIBarrierRes: 0
Itartion 3. I am 0 of 3. MPIBarrierRes: 0
Itartion 4. I am 0 of 3. MPIBarrierRes: 0
Itartion 0. I am 1 of 3. MPIBarrierRes: 0
Itartion 1. I am 1 of 3. MPIBarrierRes: 0
Itartion 2. I am 1 of 3. MPIBarrierRes: 0
Itartion 3. I am 1 of 3. MPIBarrierRes: 0
Itartion 4. I am 1 of 3. MPIBarrierRes: 0
或介于两者之间的东西,例如
Itartion 0. I am 1 of 3. MPIBarrierRes: 0
Itartion 0. I am 0 of 3. MPIBarrierRes: 0
Itartion 1. I am 0 of 3. MPIBarrierRes: 0
Itartion 0. I am 2 of 3. MPIBarrierRes: 0
Itartion 1. I am 1 of 3. MPIBarrierRes: 0
Itartion 2. I am 0 of 3. MPIBarrierRes: 0
Itartion 1. I am 2 of 3. MPIBarrierRes: 0
Itartion 2. I am 1 of 3. MPIBarrierRes: 0
Itartion 3. I am 0 of 3. MPIBarrierRes: 0
Itartion 2. I am 2 of 3. MPIBarrierRes: 0
Itartion 3. I am 1 of 3. MPIBarrierRes: 0
Itartion 4. I am 0 of 3. MPIBarrierRes: 0
Itartion 3. I am 2 of 3. MPIBarrierRes: 0
Itartion 4. I am 1 of 3. MPIBarrierRes: 0
Itartion 4. I am 2 of 3. MPIBarrierRes: 0
谁能告诉我 MPI_Barrier 和循环之间是否存在冲突? (我只发现了在不同任务中使用不同大小的循环来避免死锁的警告。) 如果有,我能做些什么来强制任务在开始循环的新迭代之前相互等待? 如果没有,这段代码有什么问题?
谢谢!
【问题讨论】:
-
能否在 printf 语句下方放置另一个 MPI_Barrier 并检查问题是否仍然存在?