dispatch_cascade.c   [plain text]

#include <stdio.h>
#include <dispatch/dispatch.h>
#include <unistd.h>
#include <stdlib.h>

#include "dispatch_test.h"

int done = 0;

#define QUEUES 80
dispatch_queue_t queues[QUEUES];


#define BLOCKS 10000
union {
	size_t index;
	char padding[64];
} indices[BLOCKS];

size_t iterations = QUEUES * BLOCKS * 0.25;

void
histogram(void) {
	size_t counts[QUEUES] = {};
	size_t maxcount = 0;
	
	size_t q;
	for (q = 0; q < QUEUES; ++q) {
		size_t i;
		for (i = 0; i < BLOCKS; ++i) {
			if (indices[i].index == q) {
				++counts[q];
			}
		}
	}
	
	for (q = 0; q < QUEUES; ++q) {
		if (counts[q] > maxcount) {
			maxcount = counts[q];
		}
	}
	
	printf("maxcount = %ld\n", maxcount);
	
	size_t x,y;
	for (y = 20; y > 0; --y) {
		for (x = 0; x < QUEUES; ++x) {
			double fraction = (double)counts[x] / (double)maxcount;
			double value = fraction * (double)20;
			printf("%s", (value > y) ? "*" : " ");
		}
		printf("\n");
	}
}

void
cascade(void* context) {
	size_t idx, *idxptr = context;

	if (done) return;
	
	idx = *idxptr + 1;

	if (idx < QUEUES) {
		*idxptr = idx;
		dispatch_async_f(queues[idx], context, cascade);
	}

	if (__sync_sub_and_fetch(&iterations, 1) == 0) {
		done = 1;
		histogram();
		test_stop();
		exit(0);
	}
}

int
main(int argc __attribute__((unused)), char* argv[] __attribute__((unused))) {
	int i;

	test_start("Dispatch Cascade");
	
	for (i = 0; i < QUEUES; ++i) {
		queues[i] = dispatch_queue_create(NULL, NULL);
	}

	for (i = 0; i < BLOCKS; ++i) {
		cascade(&indices[i].index);
	}

	dispatch_main();

	return 0;
}