C++ Multi-Thread Execution Speed Slow-Down

I am writing a multi-threaded c++ application. When thread A has a very computationally expensive operation to perform, it slows 开发者_StackOverflow中文版down threads B, C, and D. How can I prevent this?

On windows you can use Sleep(0) to release the remainder of your timeslice for other threads that are waiting.

Hard to tell without seeing code so I can only give you the advice to lower Thread A's priority. This can be done using the SetThreadPriority function.

Note that you can set the thread priorities (SetThreadPriority)

Also, I advice the backgroundworker picks it's work from a queue. The queue can then be used as a way to throttle the calculations:

• you can configure how many 'tasks' are taken from the queue for processing in one swoop
• you can lock the queue (use semaphores + condition event) so you can temporarily prevent new tasks from being picked up.
• you can now distribute the load across more workers (say if thread B, C, D are temporarily idle, they can start to lift the work off thread A; very useful on a Quad-core + desktop)

$0.02

There are a couple of ways:

• As RedX suggested, add Sleep(0) in thread A's inner loop to have it yield time more frequently. This is the cheap and lazy solution.
• Better would be to change the thread priority. When you call CreateThread, pass CREATE_SUSPENDED so that the thread does not start immediately. Then call SetPriorityClass to set the thread to a lower priority, followed by ResumeThread.

You might also want to look at having your compute-bound thread yield the processor to other threads. See this post for various ways to do this.