并行处理-从站是否生成数据集？

问题描述

| 在我的并行编程书中，我遇到了这段代码，该代码说从服务器生成数据集，但是，我认为主服务器是从手工生成数据集的。 特别是这行，是我相信master会生成数据集的原因。

for (i=0; i < ARRAY_SIZE; i++) 
        numbers[i] = i; 

有人可以确认主机还是从机生成数据集吗？

#include \"mpi.h\" 
#include <stdio.h> 
#include <math.h> 
#include <stdlib.h> 

#define TRIALS 20 
#define ARRAY_SIZE 1000000 

int main(int argc,char *argv[]) 
{ 
    int myid,numprocs; 
    double startwtime,endwtime; 
    int namelen; 
    int* numbers = new int[ARRAY_SIZE]; 
    int i,j,sum,part_sum; 
    int s,s0,startIndex,endIndex; 
    double totalTime; 

    char processor_name[MPI_MAX_PROCESSOR_NAME]; 

    MPI_Init(&argc,&argv); 
    MPI_Comm_size(MPI_COMM_WORLD,&numprocs); 
    MPI_Comm_rank(MPI_COMM_WORLD,&myid); 
    MPI_Get_processor_name(processor_name,&namelen); 

    fprintf(stderr,\"Process %d on %s\\n\",myid,processor_name); 
    fflush(stderr); 

    for (i=0; i < ARRAY_SIZE; i++) 
        numbers[i] = i; 

    if (myid == 0) 
    { 
        s = (int) floor(ARRAY_SIZE/numprocs); 
        s0 = s + ARRAY_SIZE%numprocs; 
        //printf(\"s=%d,s0= %d\\n\",s,s0); 
    } 

    MPI_Bcast(&s,1,MPI_INT,MPI_COMM_WORLD); 
    MPI_Bcast(&s0,MPI_COMM_WORLD); 

    startIndex = s0 + (myid - 1)*s; 
    endIndex = startIndex + s; 

    totalTime = 0; 

    for (j = 1; j <= TRIALS; j++) 
    { 
        if (myid == 0) 
        { 
            startwtime = MPI_Wtime(); 
        } 

        sum = 0; 
        part_sum = 0; 

        if (myid == 0) // master 
        { 
            // compute sum of master\'s numbers 
            for (i = 0; i < s0; i++) 
            { 
                part_sum += numbers[i]; 
            } 
        } 
        else 
        { 
            for (i = startIndex; i < endIndex; i++) 
            { 
                part_sum += numbers[i]; 
            } 
        } 
        MPI_Reduce(&part_sum,&sum,MPI_SUM,MPI_COMM_WORLD); 
        if (myid == 0) 
        { 
            double runTime; 
            endwtime = MPI_Wtime(); 
            runTime = endwtime - startwtime; 

            printf(\"Trial %d : Execution time (sec) = %f\\n\",runTime); 
            printf(\"Sum = %d \\n\",sum); 
            totalTime += runTime; 
        } 
    } // end for 
    if (myid == 0) 
        printf(\"Average time for %d trials = %f\",TRIALS,totalTime/TRIALS); 

    MPI_Finalize(); 
} 

    

解决方法

主机和从机都生成整个阵列。您必须记住，您的程序在所有节点上运行，并且所讨论的代码部分无法区分主/从。因此，您的书的措词没有错，但可以澄清。 :)