FFTW 3.x in octave (Was Re: [Fwd: Re: rfftw slower...])

[Dmitri A Sergatskov]

First of all I think we should drop 2.1.5.

I have an impression that FFTW guys support 2.1.x only because 
3.0.x still does not have MPI interface (plus, perhaps, due to
some contractual obligations). It will not last long.

fftpack included with octave provides a reasonable default/fallback 
option. 

Second, the way to deal with "wisdom". (I may say some thing stupid 
here since I am not quite sure I understand how this thing works.)
I would think that import should be implicit, i.e. on octave
startup it tries to import wisdom from canonical places like:
$HOME/.fftw3/wisdom:$OCTAVE_HOME/fftw3/wisdom:/etc/fftw3/wisdom
So, if one gets bad performance with system default (/etc/fftw3/wisdom)
she can create your own. 

'make wisdom' should create and put 
wisdom into octave location. I guess the latter is recommended 
step since FFTW recommends generating new wisdom for each binary.

If importing wisdom on startup undesirable (due to memory usage or
something like that), perhaps we can have global variable to 
go to .octaverc like fftw_wisdom (0 -> do not import, 1 ->
import on startup, 2 -> import on first use). 

Regards,

Dmitri.