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cannam@127:There is a fair amount of overhead involved in synchronizing threads, cannam@127: so the optimal number of threads to use depends upon the size of the cannam@127: transform as well as on the number of processors you have. cannam@127:
cannam@127:As a general rule, you don’t want to use more threads than you have cannam@127: processors. (Using more threads will work, but there will be extra cannam@127: overhead with no benefit.) In fact, if the problem size is too small, cannam@127: you may want to use fewer threads than you have processors. cannam@127:
cannam@127:You will have to experiment with your system to see what level of
cannam@127: parallelization is best for your problem size. Typically, the problem
cannam@127: will have to involve at least a few thousand data points before threads
cannam@127: become beneficial. If you plan with FFTW_PATIENT, it will
cannam@127: automatically disable threads for sizes that don’t benefit from
cannam@127: parallelization.
cannam@127:
cannam@127: