我使用MPI并行化循环[0, max ]。我想要一个主进程(让我们说进程0)最初将该循环划分为一小组 n 任务(n次迭代),然后逐步影响一组任务 x 只要一个人完成之前的工作(上一组任务),就会有进程。换句话说,我想使用MPI的阻塞和/或非阻塞发送/接收来实现负载平衡算法,但不知道如何继续。另外,有没有办法在" max"的函数中找到一组任务的最佳大小(n参数)。和" x" ?
非常感谢你的帮助。
答案 0 :(得分:0)
我终于从here找到了以下代码,它基本上是基于MPI Master / Slave模型的动态负载平衡的骨架,正是我所寻找的。我仍然无法看到如何最佳地划分初始工作集。
#include <mpi.h>
#define WORKTAG 1
#define DIETAG 2
main(argc, argv)
int argc;
char *argv[];
{
int myrank;
MPI_Init(&argc, &argv); /* initialize MPI */
MPI_Comm_rank(
MPI_COMM_WORLD, /* always use this */
&myrank); /* process rank, 0 thru N-1 */
if (myrank == 0) {
master();
} else {
slave();
}
MPI_Finalize(); /* cleanup MPI */
}
master()
{
int ntasks, rank, work;
double result;
MPI_Status status;
MPI_Comm_size(
MPI_COMM_WORLD, /* always use this */
&ntasks); /* #processes in application */
/*
* Seed the slaves.
*/
for (rank = 1; rank < ntasks; ++rank) {
work = /* get_next_work_request */;
MPI_Send(&work, /* message buffer */
1, /* one data item */
MPI_INT, /* data item is an integer */
rank, /* destination process rank */
WORKTAG, /* user chosen message tag */
MPI_COMM_WORLD);/* always use this */
}
/*
* Receive a result from any slave and dispatch a new work
* request work requests have been exhausted.
*/
work = /* get_next_work_request */;
while (/* valid new work request */) {
MPI_Recv(&result, /* message buffer */
1, /* one data item */
MPI_DOUBLE, /* of type double real */
MPI_ANY_SOURCE, /* receive from any sender */
MPI_ANY_TAG, /* any type of message */
MPI_COMM_WORLD, /* always use this */
&status); /* received message info */
MPI_Send(&work, 1, MPI_INT, status.MPI_SOURCE,
WORKTAG, MPI_COMM_WORLD);
work = /* get_next_work_request */;
}
/*
* Receive results for outstanding work requests.
*/
for (rank = 1; rank < ntasks; ++rank) {
MPI_Recv(&result, 1, MPI_DOUBLE, MPI_ANY_SOURCE,
MPI_ANY_TAG, MPI_COMM_WORLD, &status);
}
/*
* Tell all the slaves to exit.
*/
for (rank = 1; rank < ntasks; ++rank) {
MPI_Send(0, 0, MPI_INT, rank, DIETAG, MPI_COMM_WORLD);
}
}
slave()
{
double result;
int work;
MPI_Status status;
for (;;) {
MPI_Recv(&work, 1, MPI_INT, 0, MPI_ANY_TAG,
MPI_COMM_WORLD, &status);
/*
* Check the tag of the received message.
*/
if (status.MPI_TAG == DIETAG) {
return;
}
result = /* do the work */;
MPI_Send(&result, 1, MPI_DOUBLE, 0, 0, MPI_COMM_WORLD);
}
}