dispatch_apply

void dispatch_apply(size_t iterations, dispatch_queue_t queue, void (^block)(size_t));

The function submits a block to a dispatch queue for multiple invocations. It takes three arguments; the first specifies the number of iterations to perform; the second specifies a queue to which the block is submitted; and the third is the block itself, which in turn takes a single argument—the current index of the iteration.