[julia-users] FFTW.REDFT00 and FFT.RODFT00 are ~10x slower than other routines?

[Sheehan Olver]

I get the following timings with the various FFTW routines, where I ran 
each line multiple times to make sure it was accurate.  Why are REDFT00 and 
RODFT00 almost 10x slower?


r=rand(100000)
@time FFTW.r2r(r,FFTW.REDFT00) #0.26s
@time FFTW.r2r(r,FFTW.REDFT01) #0.0033s
@time FFTW.r2r(r,FFTW.REDFT10) #0.0035s
@time FFTW.r2r(r,FFTW.REDFT11) #0.0033s
@time FFTW.r2r(r,FFTW.RODFT00) #0.017s
@time FFTW.r2r(r,FFTW.RODFT01) #0.0035s
@time FFTW.r2r(r,FFTW.RODFT10) #0.0035s
@time FFTW.r2r(r,FFTW.RODFT11) #0.0035s
@time fft(r)                   #0.0033s