#include <stdio.h>

#include <stdlib.h>

#include <pthread.h>

#define N 4

int A[N][N], sum[N];



void *func(void *arg)           // threads function

{

    int j, row;

    pthread_t tid = pthread_self();         // get thread ID number

    row = (int)arg;                         // get row number from arg

    printf("Thread %d [%lu] computes sum of row %d\n", row, tid, row);

    for (j=0; j<N; j++)         // compute sum of A[row]in global sum[row]

        sum[row] += A[row][j];

    printf("Thread %d [%lu] done: sum [%d] = %d\n",

                    row, tid, row, sum [row]);

    pthread_exit((void* )0);    // thread exit: 0=normal termination

}



int main (int argc, char *argv [])

{

    pthread_t thread[N];        // thread IDs

    int i, j, r, total = 0;

    void *status;

    printf("Main: initialize A matrix\n");

    for (i=0; i<N; i++){

        sum[i] = 0;

        for (j=0; j<N; j++){

            A[i][j] = i*N + j + 1;

            printf("%4d ", A[i][j]);

        }

        printf("\n");

    }

    printf("Main: create %d threads\n", N);

    for(i=0; i<N; i++){

        pthread_create(&thread[i], NULL, func, (void *)i);

    }

    printf("Main: try to join with threads\n");

    for(i=0; i<N; i++) {

        pthread_join(thread[i], &status);

        printf("Main: joined with %d [%lu]: status=%d\n",

                                i, thread[i], (int)status);

    }

    printf("Main: compute and print total sum: ");

    for (i=0; i<N; i++)

        total += sum[i];

    printf("tatal = %d\n", total);

    pthread_exit(NULL);

}