89 lines
1.9 KiB
C
89 lines
1.9 KiB
C
/*任务4(必做）：编译、测试和运行示例程序psum64.c
|
||
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。
|
||
2）改写该程序psum64.c,保存为task64.c，实现计算02+12+… +(n-1)2功能。
|
||
*/
|
||
|
||
#include <stdio.h>
|
||
#include <stdlib.h>
|
||
#include <pthread.h>
|
||
#include <semaphore.h>
|
||
#include <sys/time.h>
|
||
|
||
double get_time()
|
||
{
|
||
struct timeval tv;
|
||
gettimeofday(&tv, NULL);
|
||
return tv.tv_sec + tv.tv_usec / 1000000.0;
|
||
}
|
||
|
||
#define MAXTHREADS 16
|
||
|
||
void *sum(void *vargp);
|
||
|
||
unsigned long long psum64[MAXTHREADS];
|
||
unsigned long long nelems_per_thread;
|
||
|
||
int main(int argc, char **argv)
|
||
{
|
||
unsigned long long i,nelems,log_nelems,nthreads,result = 0;
|
||
pthread_t tid[MAXTHREADS];
|
||
int myid[MAXTHREADS];
|
||
|
||
if(argc != 3)
|
||
{
|
||
printf("Usage: %s <nthreads> <log_nelems>\n",argv[0]);
|
||
exit(0);
|
||
}
|
||
nthreads = atoi(argv[1]);
|
||
log_nelems = atoi(argv[2]);
|
||
nelems = (1LL << log_nelems);
|
||
nelems_per_thread = nelems / nthreads;
|
||
|
||
double t_start = get_time();
|
||
for ( i = 0; i < nthreads; i++)
|
||
{
|
||
myid[i] = i;
|
||
pthread_create(&tid[i],NULL,sum,&myid[i]);
|
||
}
|
||
|
||
for ( i = 0; i < nthreads; i++)
|
||
{
|
||
pthread_join(tid[i],NULL);
|
||
}
|
||
|
||
for ( i = 0; i < nthreads; i++)
|
||
{
|
||
result += psum64[i];
|
||
}
|
||
|
||
if (result == (nelems*(nelems-1))/2)
|
||
{
|
||
printf("Correct result: %llu\n",result);
|
||
}
|
||
else
|
||
{
|
||
printf("Wrong result: %llu\n",result);
|
||
}
|
||
double t_end = get_time();
|
||
printf("Time taken: %f seconds\n", t_end - t_start);
|
||
|
||
exit(0);
|
||
}
|
||
|
||
|
||
|
||
void *sum(void *vargp)
|
||
{
|
||
int myid = *((int *)vargp);
|
||
unsigned long long begin = myid * nelems_per_thread;
|
||
unsigned long long end = begin + nelems_per_thread;
|
||
unsigned long long i,lsum=0;
|
||
|
||
for (i = begin; i < end; i++)
|
||
{
|
||
lsum += i;
|
||
}
|
||
|
||
psum64[myid] = lsum;
|
||
return NULL;
|
||
} |