Question

Does the Grand Central Dispatch API allow an execution context (thread) to query any thread-specific state during runtime? Specifically, is there a GCD equivalent to the OpenMP call
omp_get_thread_num()?

Answer 1

If you would like to execute an operation n-times to a bunch of things (like an map operation), you can use dispatch_apply.

dispatch_apply(10, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, NULL), ^(size_t index) {
    void * my_thing =  my_tings[index];
    // ...
});