#include #include #include #include //#include #include //for yielding when idle //define size of thread pool #define NTHREADS 5 int fact = 1; //global common result /* Thread process */ void* thread_mul(void* param) { pthread_mutex_t mtx; int res; //pthread result int myNum; int state = 1, durcount = 0; //deduce thread # from first //time run parameter myNum = *(int*)param - 2; printf("%d: at work\n", myNum); fflush(stdout); while (*(int*)param>=0) { if (*(int*)param>0) { if (state==0) { printf("%d: resume after idle for %d time slices\n", myNum, durcount); fflush(stdout); durcount = 0; state = 1; } //begin critical section res = pthread_mutex_lock(&mtx); if (res==0) { //update shared factorial value fact *= *(int*)param; res = pthread_mutex_unlock(&mtx); //end of critical section printf("%d: (*%d) done\n", myNum, *(int*)param); fflush(stdout); if (res) { fprintf(stderr, "%d: error in mutex unlock #%d.\n", res, myNum); fflush(stderr); } sched_yield(); } else { fprintf(stderr, "%d: %d error in mutex lock.\n", myNum, res); fflush(stderr); exit(3); } *(int*)param = 0; } else { state = 0; durcount++; sched_yield(); } } if (state==0) { printf("%d: idle for %d time slices\n", myNum, durcount); fflush(stdout); durcount = 0; state = -1; } printf("%d: exit\n", myNum); return (NULL); } int main() { pthread_t hdlThreads[NTHREADS]; //shared thread input/status: //-1 means no longer needed // 0 means done/idle //>1 is input value to multiply int j[NTHREADS]; int res; //pthread result int n; int durcount[NTHREADS] = {0}; puts("main: begin"); fflush(stdout); //Does this environment allow threads? if (sysconf(_SC_THREADS)==-1) { printf("Threads are unsupported.\n"); fflush(stdout); exit(1); } //input value to factorialize scanf("%d", &n); //initialize thread statuses for (int i = 0; i0) { durcount[t]++; t++; if (t >= NTHREADS) { t = 0; } sched_yield(); } if (durcount[t]) { printf("main: %d busy for %d time slices\n", t, durcount[t]); fflush(stdout); durcount[t] = 0; } int oldJ = j[t]; j[t] = i + 2; // 2 through n if (oldJ<0) { printf("main: new thread %d (*%d)\n", t, j[t]); fflush(stdout); res = pthread_create( &hdlThreads[i], NULL, thread_mul, &j[t]); if (res) { printf("Error = %d. Thread creation #%d failed.\n", res, j[t]); fflush(stdout); exit(2); } } else printf("main: re-assign %d (*%d)\n", t, j[t]); } //resync threads and shut down int busy; do { fflush(stdout); busy = 0; for(int i = 0; i0) { busy = 1; durcount[i]++; sched_yield(); } if (j[i]==0) { j[i] = -1; if (durcount[i]) { printf("main: %d busy for %d time slices\n", i, durcount[i]); durcount[i] = 0; } //res = pthread_join(hdlThreads[i], NULL); } } } while (busy); //for(int i = 0; i

Factorial by multithreading