Might be worth creating a plan with FFTW.MEASURE or FFTW.EXHAUSTIVE. See help for `plan_fft`.
FYI, this isn't really a "Julia issue" since Julia is just calling the FFTW library. Best, --Tim On Sunday, December 20, 2015 03:40:41 PM Pontus Stenetorp wrote: > On 19 December 2015 at 20:02, <[email protected]> wrote: > >> As can be seen, all the 8 cores of my pc is being used by the julia > >> program, however, only 35% of the system resource is covered. My julia > >> code > >> mainly does the fft operates in a loop. I use fftw.set_num_threads(8) > >> outside the loop. In my opinion, the top command should exhibit nearly > >> 100% use of the system resource, but that's not true. > > > > I'm not quite sure where you get 35% from, as I read your `top` the top > > three users are Julia using 6.89 cpus, QQ.exe 0.45 cpu and X 0.11 cpu. > > Julia is getting the vast majority of the cpu resources, nearly 7 out of 8 > > cores. > > He is reading time spent in user space which is given as 35.0%, the > problem however is that 60.6% of the time is spent on kernel processes > which is a really bad sign. Without seeing the code it is difficult > to know what is going on, especially since I am not familiar with > FFTW. My best guess is that the job is I/O bound or that the data > given to FFTW is so small that the thread overhead is eating up > performance. For the latter, set the number of threads to one and see > if the performance improves. > > Pontus
