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// Copyright 2015 The Emscripten Authors. All rights reserved.
// Emscripten is available under two separate licenses, the MIT license and the
// University of Illinois/NCSA Open Source License. Both these licenses can be
// found in the LICENSE file.
// This file tests pthread barrier usage.
#include <pthread.h>
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#define N 100
#define THREADS 8
int matrix[N][N] = {};
int intermediate[N] = {};
// Barrier variable
pthread_barrier_t barr;
// Sums a single row of a matrix.
int sum_row(long r)
{
int sum = 0;
for(int i = 0; i < N; ++i)
sum += matrix[r][i];
return sum;
}
void *thread_main(void *arg)
{
// Each thread sums individual rows.
long id = (long)arg;
for(long i = id; i < N; i += THREADS)
intermediate[i] = sum_row(i);
// Synchronization point
int rc = pthread_barrier_wait(&barr);
if (rc != 0 && rc != PTHREAD_BARRIER_SERIAL_THREAD)
{
printf("Could not wait on barrier\n");
exit(-1);
}
// Then each thread sums the one intermediate vector.
int totalSum = 0;
for(int i = 0; i < N; ++i)
totalSum += intermediate[i];
pthread_exit((void*)totalSum);
}
int main(int argc, char **argv)
{
pthread_t thr[THREADS];
// Create the matrix and compute the expected result.
int expectedTotalSum = 0;
srand(time(NULL));
for(int i = 0; i < N; ++i)
for(int j = 0; j < N; ++j)
{
matrix[i][j] = rand();
expectedTotalSum += matrix[i][j];
}
printf("The sum of the matrix is %d.\n", expectedTotalSum);
// Barrier initialization
int ret = pthread_barrier_init(&barr, NULL, THREADS);
assert(ret == 0);
for(int i = 0; i < THREADS; ++i) pthread_create(&thr[i], NULL, &thread_main, (void*)i);
for(int i = 0; i < THREADS; ++i)
{
int totalSum = 0;
pthread_join(thr[i], (void**)&totalSum);
assert(totalSum == expectedTotalSum);
}
return 0;
}
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