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dispatch_apply(3) | Library Functions Manual | dispatch_apply(3) |
NAME¶
dispatch_apply — schedule blocks for iterative executionSYNOPSIS¶
#include <dispatch/dispatch.h> voiddispatch_apply(size_t iterations, dispatch_queue_t queue, void (^block)(size_t)); void
dispatch_apply_f(size_t iterations, dispatch_queue_t queue, void *context, void (*function)(void *, size_t));
DESCRIPTION¶
The dispatch_apply() function provides data-level concurrency through a "for (;;)" loop like primitive:dispatch_queue_t the_queue = dispatch_get_concurrent_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT); size_t iterations = 10; // 'idx' is zero indexed, just like: // for (idx = 0; idx < iterations; idx++) dispatch_apply(iterations, the_queue, ^(size_t idx) { printf("%zu\n", idx); });
#define STRIDE 3 dispatch_apply(count / STRIDE, queue, ^(size_t idx) { size_t j = idx * STRIDE; size_t j_stop = j + STRIDE; do { printf("%zu\n", j++); } while (j < j_stop); }); size_t i; for (i = count - (count % STRIDE); i < count; i++) { printf("%zu\n", i); }
FUNDAMENTALS¶
Conceptually, dispatch_apply() is a convenient wrapper around dispatch_async() and a semaphore to wait for completion. In practice, the dispatch library optimizes this function. The dispatch_apply() function is a wrapper around dispatch_apply_f().SEE ALSO¶
dispatch(3), dispatch_async(3), dispatch_queue_create(3), dispatch_semaphore_create(3)May 1, 2009 | Darwin |