On Wednesday, June 18, 2014 11:54:33 PM Ethan Anderes wrote: > That does it! I never would have guessed that dims would refer to the side > length of the matrix. Thanks a ton.
There is an unfortunate confusion surrounding "dims": in most places it refers to the size of an array (similar to "the dimensions of a room"), but in some other places we use it to refer to "which dimensions?" (as in, "which axes?"). In some other places, that latter parameter is called "region." Would be great to clean this up somehow. --Tim > > On Wednesday, June 18, 2014 11:47:47 PM UTC-7, Alex wrote: > > Hi Ethan, > > > > irfft and brfft take an additional argument d, which roughly speaking > > denotes the size of the transformed matrix. See also the docs on brfft > > and irfft > > <http://julia.readthedocs.org/en/latest/stdlib/base/?highlight=brfft#Base. > > brfft> > > > > The following should work for you > > julia> a = rand(64, 64); > > > > julia> a_from_rfft = rfft(a); > > > > julia> back_to_a = irfft(a_from_rfft, size(a,1)); > > > > julia> norm(back_to_a-a) > > 5.185263941656865e-15 > > > > Hope that helps, > > > > Alex. > > > > On Thursday, 19 June 2014 06:37:38 UTC+2, Ethan Anderes wrote: > >> Does anyone have experience with brfft or irfft? I’m trying to optimize > >> some code and I noticed a huge performance gain if I use rfft over fft > >> for > >> 2-d real matrices. However > >> I need to filter in the Fourier domain, then use irfft (or brfft) to > >> return to spatial corridinates but I can’t seem to get irfft or brfft to > >> work. > >> > >> a = rand(1024, 1024); > >> > >> a_from_fft = fft(a); > >> a_from_rfft = rfft(a); > >> > >> ### each one of these gives an error > >> back_to_a = brfft(a_from_fft); > >> back_to_a = brfft(a_from_rfft); > >> back_to_a = irfft(a_from_fft); > >> back_to_a = irfft(a_from_rfft); > >> > >> Here is my version info > >> > >> julia> versioninfo() > >> > >> Julia Version 0.3.0-prerelease+3730 > >> Commit 8f1fbec (2014-06-17 23:55 UTC) > >> > >> Platform Info: > >> System: Darwin (x86_64-apple-darwin13.2.0) > >> CPU: Intel(R) Core(TM) i5-4250U CPU @ 1.30GHz > >> WORD_SIZE: 64 > >> BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY) > >> LAPACK: libopenblas > >> LIBM: libopenlibm > >> > >>
