I was looking at the thread creation API.
Exactly, why do we use PTHREAD_SCOPE_SYSTEM instead of PTHREAD_SCOPE_PROCESS ?
http://source.winehq.org/git/wine.git/? ... ead.c#l611
What is the technical difference?
I remember, some years ago, that on SunOS 8 setting the latter it would make one thread only scheduled globally for the process, instead, using the first would let the process use at the same time multiple threads on multiple processors (so a proper multithread application).
Today I tested it with Ubuntu 8.10 and gcc/g++ 4.3.2 and actually there's no difference (on my Intel dual core).
Anyone does know what is the benefit from switching from one to other option?
Attaching some stupid code used for MT testing:
Code: Select all
#include <iostream>
#include <cmath>
#include <pthread.h>
extern "C" void *my_th(void *param) {
const unsigned int CNT=1024;
double mysum=0.0;
for(unsigned int j = 0; j< CNT; j++)
for(unsigned int k=0; k < CNT; k++)
for(unsigned int i=0; i<CNT; i++)
mysum += i;
std::cout << "mysum: " << mysum << std::endl;
return 0;
}
int main(int argc, char *argv[]) {
pthread_t pthread_id, pthread_id2;
pthread_attr_t attr;
pthread_attr_init(&attr);
pthread_attr_setscope(&attr, PTHREAD_SCOPE_PROCESS);
std::cout << "first thread: " << pthread_create(&pthread_id, &attr, my_th, 0) << std::endl;
std::cout << "second thread: " << pthread_create(&pthread_id2, &attr, my_th, 0) << std::endl;
pthread_attr_destroy(&attr);
pthread_join(pthread_id, 0);
pthread_join(pthread_id2, 0);
}
Cheers,
