#include <pthread.h>
#include <stdio.h>
#include <time.h>

typedef struct {
    int i;
    int loops;
    pthread_mutex_t mutex;
} shared;

void *worker( void *arg ) {
    shared *s = (shared*)arg;
    int i = 0;


    for( i=0; i < s->loops; ++i ) {
         pthread_mutex_lock( &s->mutex );
         ++s->i;
         pthread_mutex_unlock( &s->mutex );
    }
    return;
}

int main( int argc, char **argv ) {
    int i = 0, nThreads = 4;
    clock_t start, finish;
    double elapsed;
    pthread_t threads[32];
    shared s = { 0, 1000000 };;

    pthread_mutex_init( &s.mutex, NULL );

    if( argc > 1 ) nThreads = atoi( argv[1] );
    if( argc > 2 ) s.loops = atoi( argv[2] );

    printf( "threads:%d loops:%d\n", nThreads, s.loops );

    start = clock();
    for( i=0; i < nThreads; ++i )
         pthread_create( &threads[ i ], NULL, &worker, &s );

    for( i=0; i < nThreads; ++i )
        pthread_join( threads[ i ], NULL );
    finish = clock();

    elapsed = (double)(finish - start) / CLOCKS_PER_SEC;

    printf( "count: %u time:%.6f\n", s.i, elapsed );

}