CODEWITHSUNDEEP
linuxpthreads
hello c
hello c

Reputation: 43

how can I implement fast barrier?

Now i implement my barrier. but it didn't work well.

When i run barrier time calculate code pthread_barrier_wait consume 180000 us my barrier consume 390000 us

i don't know why and i want to make more fast barrier

Here is my barrier code

 82 pthread_mutex_t     mutexwait1;
 83 int wait_count = NUM_THREADS;
 84 int barrier1234(void) {                                                     
 85 
 86     int status, cancel, tmp;
 87     status = pthread_mutex_lock(&mutexwait1);
 88     wait_count = wait_count - 1;
 89     if(wait_count == 0){ 
 90         pthread_cond_broadcast(&cond1);
 91         wait_count = NUM_THREADS ;  
 92     }   
 93     else
 94         status = pthread_cond_wait(&cond1, &mutexwait1);
 95 
 96     pthread_mutex_unlock(&mutexwait1);
 97     return status;
 98 
 99 }

I find some barrier_wait function but it didn't work. ( download from glibc) => error message(structure variable is not matching) is occur when compile barrier => I wonder this error is caused by version

I am using ubuntu 10.04 Please teach me why my barrier is slow. And how can i implement default pthread_barrier_wait (in my platform)

Upvotes: 0

Views: 1136

Answers (1)

Kaz
Kaz

Reputation: 58598

glibc's barrier is implemented using lower level primitives, and not a mutex and condition.

Your mutex-based implementation has the obvious problem that it requires every thread which wakes up to re-acquire the mutex only to release it. This goes against the spirit of what a barrier is about: a first class primitive in its own right. (Of course, it's a good way to do a quick and dirty port of code that requires barriers to a platform that provides only mutexes and conditions.)

I wrote the first POSIX barrier functions that existed in glibc some twelve years ago, by the way. Wink!

Upvotes: 2

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