我必须实现减少总和，它从参数计算从0到特定数字的总和。我使用以下内容从变量中获取总和，但我不知道如何使用参数并使用我的主进程计算进程的总和。我如何使用参数进行此操作。我使用OpenMPI库。
#include "mpi.h"
#include <stdio.h>
#include <stdlib.h>
#define ARRAYSIZE 16
#define MASTER 0
float data[ARRAYSIZE];
int main (int argc, char *argv[])
{
int numtasks, taskid, rc, dest, offset, i, j, tag1, tag2, source, chunksize;
float mysum, sum;
float update(int myoffset, int chunk, int myid);
MPI_Status status;
/***** Initializations *****/
MPI_Init(&argc, &argv);
MPI_Comm_size(MPI_COMM_WORLD, &numtasks);
if (numtasks % 4 != 0) {
printf("Quitting. Number of MPI tasks must be divisible by 4.\n");
MPI_Abort(MPI_COMM_WORLD, rc);
exit(0);
}
MPI_Comm_rank(MPI_COMM_WORLD,&taskid);
printf ("MPI task %d has started...\n", taskid);
chunksize = (ARRAYSIZE / numtasks);
tag2 = 1;
tag1 = 2;
/***** Master task only ******/
if (taskid == MASTER){
/* Initialize the array */
sum = 0;
for(i=0; i<ARRAYSIZE; i++) {
data[i] = i * 1.0;
sum = sum + data[i];
}
printf("Initialized array sum = %e\n",sum);
/* Send each task its portion of the array - master keeps 1st part */
offset = chunksize;
for (dest=1; dest<numtasks; dest++) {
MPI_Send(&offset, 1, MPI_INT, dest, tag1, MPI_COMM_WORLD);
MPI_Send(&data[offset], chunksize, MPI_FLOAT, dest, tag2, MPI_COMM_WORLD);
printf("Sent %d elements to task %d offset= %d\n",chunksize,dest,offset);
offset = offset + chunksize;
}
/* Master does its part of the work */
offset = 0;
mysum = update(offset, chunksize, taskid);
/* Wait to receive results from each task */
for (i=1; i<numtasks; i++) {
source = i;
MPI_Recv(&offset, 1, MPI_INT, source, tag1, MPI_COMM_WORLD, &status);
MPI_Recv(&data[offset], chunksize, MPI_FLOAT, source, tag2,
MPI_COMM_WORLD, &status);
}
/* Get final sum and print sample results */
MPI_Reduce(&mysum, &sum, 1, MPI_FLOAT, MPI_SUM, MASTER, MPI_COMM_WORLD);
printf("Sample results: \n");
offset = 0;
for (i=0; i<numtasks; i++) {
for (j=0; j<5; j++)
printf(" %e",data[offset+j]);
printf("\n");
offset = offset + chunksize;
}
printf("*** Final sum= %e ***\n",sum);
} /* end of master section */
/***** Non-master tasks only *****/
if (taskid > MASTER) {
/* Receive my portion of array from the master task */
source = MASTER;
MPI_Recv(&offset, 1, MPI_INT, source, tag1, MPI_COMM_WORLD, &status);
MPI_Recv(&data[offset], chunksize, MPI_FLOAT, source, tag2,
MPI_COMM_WORLD, &status);
mysum = update(offset, chunksize, taskid);
/* Send my results back to the master task */
dest = MASTER;
MPI_Send(&offset, 1, MPI_INT, dest, tag1, MPI_COMM_WORLD);
MPI_Send(&data[offset], chunksize, MPI_FLOAT, MASTER, tag2, MPI_COMM_WORLD);
MPI_Reduce(&mysum, &sum, 1, MPI_FLOAT, MPI_SUM, MASTER, MPI_COMM_WORLD);
} /* end of non-master */
MPI_Finalize();
} /* end of main */
float update(int myoffset, int chunk, int myid) {
int i;
float mysum;
/* Perform addition to each of my array elements and keep my sum */
mysum = 0;
for(i=myoffset; i < myoffset + chunk; i++) {
data[i] = data[i] + i * 1.0;
mysum = mysum + data[i];
}
printf("Task %d mysum = %e\n",myid,mysum);
return(mysum);
}
例如：$ mpicc -np <# of threads> a.out <number to calculate>