79 lines
1.7 KiB
C
79 lines
1.7 KiB
C
/*任务4(必做）：编译、测试和运行示例程序psum64.c
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1）测量线程数为1、2、4、8、16时程序的执行时间，计算加速比和效率，并做出解释。
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2）改写该程序psum64.c,保存为task64.c，实现计算02+12+… +(n-1)2功能。
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <pthread.h>
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#include <semaphore.h>
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#include <time.h>
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#define MAXTHREADS 16
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void *sum(void *vargp);
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unsigned long long psum64[MAXTHREADS];
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unsigned long long nelems_per_thread;
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int main(int argc, char **argv)
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{
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unsigned long long i,nelems,log_nelems,nthreads,result = 0;
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pthread_t tid[MAXTHREADS];
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int myid[MAXTHREADS];
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if(argc != 3)
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{
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printf("Usage: %s <nthreads> <log_nelems>\n",argv[0]);
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exit(0);
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}
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nthreads = atoi(argv[1]);
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log_nelems = atoi(argv[2]);
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nelems = (1LL << log_nelems);
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nelems_per_thread = nelems / nthreads;
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for ( i = 0; i < nthreads; i++)
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{
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myid[i] = i;
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pthread_create(&tid[i],NULL,sum,&myid[i]);
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}
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for ( i = 0; i < nthreads; i++)
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{
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pthread_join(tid[i],NULL);
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}
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for ( i = 0; i < nthreads; i++)
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{
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result += psum64[i];
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}
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if (result == (nelems*(nelems-1))/2)
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{
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printf("Correct result: %ld\n",result);
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}
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else
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{
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printf("Wrong result: %ld\n",result);
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}
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exit(0);
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}
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void *sum(void *vargp)
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{
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int myid = *((int *)vargp);
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unsigned long long begin = myid * nelems_per_thread;
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unsigned long long end = begin + nelems_per_thread;
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unsigned long long i,lsum=0;
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for (i = begin; i < end; i++)
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{
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lsum += i;
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}
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psum64[myid] = lsum;
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return NULL;
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} |