How can multithreading speed up an application (when threads can't run concurrently)?

Question

I\'m learning about multithreading, but after reading some tutorials I\'m sort of confused. I don\'t understand how multithreading can speed up an application.

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Answer 1

On a computer, many programs (or threads) share some resources. Suppose one thread is waiting for a specific resource (for example, it wants to write data to disk). OS can then switch to another tread to be able to continue computing using available resources. This is why it is often a good idea to put I/O operations on a separate thread, and also to put GUI in a separate thread.

Off course, multithreading will not gives you a perfect speedup, but it can help a little big increasing performances. It is even better on hyperthreading architectures, where some registers are duplicated to minimize impact of context switching.