[SciPy-dev] Question about fft overwrites; still scipy.fft problem on OS X

Pearu Peterson pearu at scipy.org
Tue Jan 10 14:50:53 CST 2006



On Tue, 10 Jan 2006, Tom Loredo wrote:

> The current scipy checkout (1544) and numpy 1863 and 1864 both
> produce "Overwriting fft" and "Overwriting ifft" warnings
> when scipy is imported.  This happens both on FC3 and on OS X
> (10.3.9), so I presume it's not unique to my machines.  Is
> this anything I need to worry about?  I have to freeze
> a numpy/scipy tarball tomorrow for a sysadmin who has to
> install them on student machines; I'll just tell him and
> the students that the warning is innocuous, if it really is.

Yes, they are. You can disable these warnings by defining env. variable

   SCIPY_IMPORT_VERBOSE=-1

> scipy's fft/ifft (scipy.fft, scipy.ifft) still give erroneous
> results on OS X, though not on FC3 (both with recent installs
> of FFTW2).  numpy.fft works fine on both platforms, so I'll
> have my students stick with that.  scipy.fft worked fine on
> OS X last week....
>
> from scipy import *
> x = arange(16)*2*pi/16
> sx = sin(x)
> sfx = fft(sx)
> sfix = ifft(sfx)
> print max(abs(sx-sfix.real))
>
> On OS X Panther this prints "1.0"; change "scipy" to "numpy" and
> it prints "1.11e-16" (or thereabouts).  On FC3, both work fine.

By any change, do you have djbfft installed? You can disable detecting 
djbfft by defining env. variable

   DJBFFT=None

Pearu




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