gettimeofday(&tv2, NULL);
int ms = (int)(1000000*(tv2.tv_sec - tv1.tv_sec) + tv2.tv_usec - tv1.tv_usec) / 1000;
printf("Th:%ld Time:%dms\n", num_threads_, ms);
gettimeofday(&tv2, NULL);
int ms = (int)(1000000*(tv2.tv_sec - tv1.tv_sec) + tv2.tv_usec - tv1.tv_usec) / 1000;
printf("Th:%ld Time:%dms\n", num_threads_, ms);