我有一个关于 C 语言 MPI 编程的基本问题。基本上我想要的是有一个主进程产生特定数量的子进程，从所有子进程中收集一些信息（等到所有子进程完成），计算一些metric，基于这个metric，它决定是否必须产生更多的线程......它会一直这样做，直到metric满足某些特定条件。我翻遍了文献，无济于事。如何才能做到这一点？任何指针？
谢谢您的帮助。
礼貌：使用 C 的消息传递接口 (MPI) 简介。在“对数组求和的完整并行程序”中，可以说，“出于某种蹩脚的原因”，我希望主进程对数组的内容求和两次。即在第一次迭代中，主进程启动计算数组总和的从进程，一旦它们完成并且主进程返回值，我想调用主进程来重新调用另一组线程来执行再次计算。为什么下面的代码不起作用？我在产生从属进程的主进程进程周围添加了一个while循环。
#include <stdio.h>
#include <mpi.h>
#define max_rows 100000
#define send_data_tag 2001
#define return_data_tag 2002
int array[max_rows];
int array2[max_rows];
main(int argc, char **argv)
{
long int sum, partial_sum,number_of_times;
number_of_times=0;
MPI_Status status;
int my_id, root_process, ierr, i, num_rows, num_procs,
an_id, num_rows_to_receive, avg_rows_per_process,
sender, num_rows_received, start_row, end_row, num_rows_to_send;
/* Now replicte this process to create parallel processes.
* From this point on, every process executes a seperate copy
* of this program */
ierr = MPI_Init(&argc, &argv);
root_process = 0;
/* find out MY process ID, and how many processes were started. */
ierr = MPI_Comm_rank(MPI_COMM_WORLD, &my_id);
ierr = MPI_Comm_size(MPI_COMM_WORLD, &num_procs);
if(my_id == root_process) {
/* I must be the root process, so I will query the user
* to determine how many numbers to sum. */
//printf("please enter the number of numbers to sum: ");
//scanf("%i", &num_rows);
num_rows=10;
while (number_of_times<2)
{
number_of_times++;
start_row=0;
end_row=0;
if(num_rows > max_rows) {
printf("Too many numbers.\n");
exit(1);
}
avg_rows_per_process = num_rows / num_procs;
/* initialize an array */
for(i = 0; i < num_rows; i++) {
array[i] = i + 1;
}
/* distribute a portion of the bector to each child process */
for(an_id = 1; an_id < num_procs; an_id++) {
start_row = an_id*avg_rows_per_process + 1;
end_row = (an_id + 1)*avg_rows_per_process;
if((num_rows - end_row) < avg_rows_per_process)
end_row = num_rows - 1;
num_rows_to_send = end_row - start_row + 1;
ierr = MPI_Send( &num_rows_to_send, 1 , MPI_INT,
an_id, send_data_tag, MPI_COMM_WORLD);
ierr = MPI_Send( &array[start_row], num_rows_to_send, MPI_INT,
an_id, send_data_tag, MPI_COMM_WORLD);
}
/* and calculate the sum of the values in the segment assigned
* to the root process */
sum = 0;
for(i = 0; i < avg_rows_per_process + 1; i++) {
sum += array[i];
}
printf("sum %i calculated by root process\n", sum);
/* and, finally, I collet the partial sums from the slave processes,
* print them, and add them to the grand sum, and print it */
for(an_id = 1; an_id < num_procs; an_id++) {
ierr = MPI_Recv( &partial_sum, 1, MPI_LONG, MPI_ANY_SOURCE,
return_data_tag, MPI_COMM_WORLD, &status);
sender = status.MPI_SOURCE;
printf("Partial sum %i returned from process %i\n", partial_sum, sender);
sum += partial_sum;
}
printf("The grand total is: %i\n", sum);
}
}
else {
/* I must be a slave process, so I must receive my array segment,
* storing it in a "local" array, array1. */
ierr = MPI_Recv( &num_rows_to_receive, 1, MPI_INT,
root_process, send_data_tag, MPI_COMM_WORLD, &status);
ierr = MPI_Recv( &array2, num_rows_to_receive, MPI_INT,
root_process, send_data_tag, MPI_COMM_WORLD, &status);
num_rows_received = num_rows_to_receive;
/* Calculate the sum of my portion of the array */
partial_sum = 0;
for(i = 0; i < num_rows_received; i++) {
partial_sum += array2[i];
}
/* and finally, send my partial sum to hte root process */
ierr = MPI_Send( &partial_sum, 1, MPI_LONG, root_process,
return_data_tag, MPI_COMM_WORLD);
}
ierr = MPI_Finalize();
}