I found that the execution time of each thread increased linearly as the thread number increased. But I did't find any synchronization code. I replace ostringsstream with snprintf and the preformance increase largely.
os: redhat 6.1 64bit
g++: g++4.4
cpu :4 core 2.0Ghz.
the code list as below:
- Code: Select all
#include <iostream>
#include <sstream>
using namespace std;
void * func(void * t)
{
int n = *((int *) t);
pthread_t pid = pthread_self();
timeval t1, t2;
gettimeofday(&t1, 0);
for(int i = 0; i < n; i++)
{
ostringstream os;
/*
char buf[255];
int ret = snprintf(buf, 30, "%d", 2000000);
buf[ret] = 0;
*/
}
gettimeofday(&t2, 0);
#define DIFF(a, b) ((b.tv_sec - a.tv_sec) + (b.tv_usec - a.tv_usec) / 1000000.0)
std::cout << pid << ":" << DIFF(t1, t2) << std::endl;
#undef DIFF
return NULL;
}
int main(int argc, char *argv[])
{
int m, n =0;
m = atoi(argv[1]);
n = atoi(argv[2]);
pthread_t tid[m];
for(int i = 0; i < m; i++)
pthread_create(&tid[i], NULL, func, &n);
for(int i = 0; i < m; i++)
pthread_join(tid[i], NULL);
return 0;