[GRASS5] Problem compiling with gdal and/or fftw

Michael Rensing michael.rensing at shaw.ca
Tue Feb 14 00:47:05 EST 2006

For anyone running into this on FC4, the fftw package automatically 
updated from version 2 to version 3 when I used yum update, but now 
there's an fftw2 and fftw2-devel package.


Glynn Clements wrote:
> Michael Rensing wrote:
>> Thanks everyone. I buess I was fooled into thinking that fftw3 would 
>> replace fftw2 in all cases when yum update automagically replaced it. 
>> I'll see if I can re-install fftw2.
>> Has anyone got a quick explanation why the two versions of fftw are not 
>> compatible?
> According to the FFTW FAQ:
> 	Question 3.1. Why not support the FFTW 2 interface in FFTW 3?
> 	FFTW 3 has semantics incompatible with earlier versions: its plans can
> 	only be used for a given stride, multiplicity, and other
> 	characteristics of the input and output arrays; these stronger
> 	semantics are necessary for performance reasons. Thus, it is
> 	impossible to efficiently emulate the older interface (whose plans can
> 	be used for any transform of the same size). We believe that it should
> 	be possible to upgrade most programs without any difficulty, however.
> Note that the FFT functionality in GRASS creates a new plan for each
> transform and discards it afterwards, so it would be a simple matter
> to update lib/gmath/fft.c to use the FFTW v3 API instead.
> Supporting both versions of the API would require more work, most of
> which would be changes the configuration and build system.
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