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invocations.c

/*

 File: invocations.c of Dispatch_Compared

 Abstract: Compare overhead of several GCD approaches with that of serial code and threads

 Version: 1.0

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*/

#include "invocations.h"

#include "benchmark.h"

#include <assert.h>

#include <pthread.h>

#include <dispatch/dispatch.h>

#include <CoreFoundation/CoreFoundation.h>

// The thread entry point routine.

void* PosixThreadNullRoutine(void* data)

    return NULL;

void* InvokeThread(int n)

    pthread_t *thread_id = (pthread_t*) malloc(n*sizeof(pthread_t));

    for (int i = 0; i < n; i++) {

        int threadError = pthread_create(&thread_id[i], NULL, PosixThreadNullRoutine, NULL);

        assert(threadError == 0);

    return thread_id;

void CleanupThread(int n, void *thread_ptr)

    pthread_t *thread_id = (pthread_t*)thread_ptr;

    for (int i = 0; i < n; i++) {

        int threadError = pthread_join(thread_id[i], NULL);

        assert(threadError == 0);

    free(thread_id);

void* InvokeDispatch(int n)

    static int dummy = 0;

    static dispatch_queue_t queue = NULL;

    if (NULL == queue) queue = dispatch_queue_create("com.apple.gcd.examples.compare.invoke", NULL);

    dispatch_suspend(queue);

    for (int i = 0; i < n; i++) {

        dispatch_async(queue, ^{ dummy = i; }); // Assign variable to avoid over-optimization

    return queue;

void CleanupDispatch(int n, void *queue_ptr)

    dispatch_queue_t queue = (dispatch_queue_t) queue_ptr;

    dispatch_resume(queue);

    dispatch_sync(queue, ^{ }); // block until queue has completed all previous work

static int global_dummy = 0;

void test_dispatch(void *ctxt)

    int* i_p = ctxt;

    global_dummy = *i_p;

void* InvokeDispatchF(int n)

    static dispatch_queue_t queue = NULL;

    if (NULL == queue) queue = dispatch_queue_create("com.apple.gcd.examples.compare.invokef", NULL);

    dispatch_suspend(queue);

    for (int i = 0; i < n; i++) {

        dispatch_async_f(queue, &i, test_dispatch); // Assign variable to avoid over-optimization

    return queue;

void CleanupDispatchF(int n, void *queue_ptr)

    dispatch_queue_t queue = (dispatch_queue_t) queue_ptr;

    dispatch_resume(queue);

    dispatch_sync(queue, ^{ }); // block until queue has completed all previous work

void* InvokeArray(int n)

    CFMutableArrayRef array = CFArrayCreateMutable(NULL, 0, NULL);

    for (int i = 0; i < n; i++) {

        char *label;

        int rc = asprintf(&label, "string #i", i);

        assert(rc > 0);

        CFStringRef str = CFStringCreateWithCString(NULL, label, kCFStringEncodingMacRoman);

        free(label);

        CFArrayAppendValue(array, str);

        CFRelease(str);

    return array;

void CleanupArray(int n, void *array_ptr)

    CFMutableArrayRef array = (CFMutableArrayRef)array_ptr;

    CFRelease(array);

void* InvokeAlloc(int n)

    void* *alloc_id = (void**)malloc(n*sizeof(void*));

    for (int i = 0; i < n; i++) {

        size_t alloc_size = sizeof(pthread_t) + sizeof(dispatch_queue_t);

        alloc_id[i] = malloc(alloc_size);

        bzero(alloc_id[i],alloc_size);

    return alloc_id;

void CleanupAlloc(int n, void *alloc_ptr)

    void* *alloc_id = (void**)alloc_ptr;

    for (int i = 0; i < n; i++) {

        free(alloc_id[i]);

void invocations_run(int i)

    benchmark_header(i);

    benchmark_function(i, "alloc", InvokeAlloc, CleanupAlloc);

    benchmark_function(i, "array", InvokeArray, CleanupArray);

    benchmark_function(i, "dsptch_f", InvokeDispatchF, CleanupDispatchF);

    benchmark_function(i, "dispatch", InvokeDispatch, CleanupDispatch);

    if (i < 1e4)

        benchmark_function(i, "fork", InvokeThread, CleanupThread);

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