iOS：如何在单个应用程序中使用多个处理器内核？

I have a computationally intensive app, and tried reducing computing times by using parallel processing. I started with GDC, but didn't reduce computing times at all. In fact, serial and concurrent queues yielded exactly the same performance. I tried it with NSThreads, still to no avail. It is as if the application would be using 1 core only. I'd appreciate hearing from anyone who had positive results in using multi-threading to increase computational throughput.I have a computationally intensive app, and tri