Chris@10: Chris@10: Chris@10: How Many Threads to Use? - FFTW 3.3.3 Chris@10: Chris@10: Chris@10: Chris@10: Chris@10: Chris@10: Chris@10: Chris@10: Chris@10: Chris@10: Chris@10: Chris@10: Chris@10: Chris@10:
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5.3 How Many Threads to Use?

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There is a fair amount of overhead involved in synchronizing threads, Chris@10: so the optimal number of threads to use depends upon the size of the Chris@10: transform as well as on the number of processors you have. Chris@10: Chris@10:

As a general rule, you don't want to use more threads than you have Chris@10: processors. (Using more threads will work, but there will be extra Chris@10: overhead with no benefit.) In fact, if the problem size is too small, Chris@10: you may want to use fewer threads than you have processors. Chris@10: Chris@10:

You will have to experiment with your system to see what level of Chris@10: parallelization is best for your problem size. Typically, the problem Chris@10: will have to involve at least a few thousand data points before threads Chris@10: become beneficial. If you plan with FFTW_PATIENT, it will Chris@10: automatically disable threads for sizes that don't benefit from Chris@10: parallelization. Chris@10: Chris@10: Chris@10: Chris@10: Chris@10: