Function numexpr_set_nthreads

numexpr3/module.cpp:209–263

        

int numexpr_set_nthreads(int n_thread_new) {
    // Set the number of threads in numexpr's VM
    int n_thread_old = gs.n_thread;
    int T, rc;
    void *status;

    // printf("numexpr_set_nthreads #1, old =%d, new =%d\n", n_thread_old, n_thread_new );
    if( n_thread_new <= 0 ) {
        fprintf(stderr, "Error. `nthreads` must be a positive integer");
        return -1;
    }
    if( n_thread_new == n_thread_old ) {
        return n_thread_old;
    }

    // Only join threads if they are not initialized or if our PID is
    //   different from that in pid var (probably means that we are a
    //   subprocess, and thus threads are non-existent).
    if( gs.init_threads_done && gs.pid == getpid() ) {
        // Tell all existing threads to finish 
        gs.barrier_passed = BARRIER_EXIT;
        pthread_mutex_lock(&gs.count_threads_mutex);
        // Ensure that workers never wait on the condition variable
        gs.count_threads = n_thread_old; 
        // Wake all workers
        pthread_cond_broadcast(&gs.count_threads_cv);
        pthread_mutex_unlock(&gs.count_threads_mutex);

        for( T=0; T < n_thread_old; T++ ) {
            // Join exiting threads 
            rc = pthread_join(gs.threads[T], &status);
            if (rc) {
                printf( "JOIN ERROR %d\n", rc );
                fprintf(stderr, "ERROR; return code from pthread_join() is %d\n", rc);
                fprintf(stderr, "    Error detail: %s\n", strerror(rc));
                exit(-1);
            }
            
        }
        pthread_mutex_unlock(&gs.count_threads_mutex);
        pthread_mutex_unlock(&gs.count_mutex);
        gs.count_threads = 0;
        gs.n_thread = n_thread_new;
        gs.init_threads_done = 0;
        gs.barrier_passed = BARRIER_HALT;
    } 
    else {
        gs.n_thread = n_thread_new;
    }

    // Launch a new pool of threads
    reinit_threads(n_thread_old);
    
    return n_thread_old;
}
PyDoc_STRVAR(SetNumThreads__doc__,
"Sets a maximum number of threads to be used in operations. Returns old value.\n");
static PyObject*