C语言实现并行求和算法
1、问题描述
将数组A均匀划分成m个片段，每个数组片段最多有(n+m-1)/m 个元素。每个数组片段分别由一个线程负责局部求和，最后这些部分和加起来就得到数组中所有元素的总和。
2、相关代码
此代码在gcc4.3下编译通过
#include <pthread.h>#include <stdio.h>#include <stdlib.h>#define NUM_THREADS 4int N;int *X;int gSum[NUM_THREADS];void* Summation(void *pArg){ int tNum= *((int *)pArg); int lSum=0; int start,end; int i; start = (N/NUM_THREADS)*tNum; printf("start is:%d\n",start); end = (N/NUM_THREADS)*(tNum+1); printf("end is:%d\n",end); if(tNum == NUM_THREADS -1) end =N; for(i=start;i<end;i++) lSum+=X[i]; gSum[tNum]=lSum; free(pArg);}void initArr(){ int i; puts("input array length:："); scanf("%d",&N); X=(int*)malloc(N*sizeof(int));// for(i=0;i<N;i++) { X[i]=i+1; printf("%d\t",X[i]); }}int main(void){ int j,sum=0; pthread_t tHandles[NUM_THREADS]; initArr(); for(j=0;j<NUM_THREADS;j++ ){ int *threadNum =malloc(4); *threadNum=j;// printf("threadNum is:%d\n",*threadNum); pthread_create(&tHandles[j],NULL,Summation,(void*)threadNum); } for(j=0;j<NUM_THREADS;j++){ pthread_join(tHandles[j],NULL); sum+= gSum[j]; } printf("the sum of array elements is %d\n",sum); return 0;}