Reply by Hans Mittelmann June 2, 20072007-06-02
>> method=fftw('planner')
method = hybrid ------------------------------------------------------------------------ On Jun 2, 2:27 pm, "Vista" <a...@gmai.com> wrote:
> Hi all, > > Matlab command "fftw" supposedly should return something, as described in > the following help document. But when I tried these command examples, > nothing happened, i.e. "fftw" returned nothing. > > What might be the problem? > > Thanks > > ------------------------------------------------------------------------------------------ > > >> help fftw > > FFTW Interface to FFTW library run-time algorithm tuning control. > The MATLAB functions FFT, IFFT, FFT2, IFFT2, FFTN, and IFFTN functions > use a library called FFTW. The FFTW library has the ability to > experimentally determine the quickest computational method to compute > the FFT of a particular size and dimensionality. The FFTW function > provides an interface to this run-time algorithm tuning. > > FFTW('planner', METHOD) sets the FFTW library planner method used for > subsequent calls to FFT, IFFT, FFT2, IFFT2, FFTN, and IFFTN. METHOD can > be one of these strings: 'estimate', 'measure', 'patient', and > 'exhaustive', or 'hybrid'. If the planner method is 'estimate', then > the FFTW library chooses algorithms based on a quick heuristic. The > resulting algorithms are sometimes suboptimal. If you specify > 'measure', the FFTW library will experiment with many different > algorithms to compute an FFT of a given size. The library caches the > result in an internal "wisdom" database so that it can reused the > next time an FFT of the same size is computed. Methods 'patient' and > 'exhaustive' are similar to 'measure' except that they take much > longer. If the planner method is 'hybrid', then MATLAB uses the > 'measure' method for FFT dimensions of 8192 or smaller, and it uses > the 'estimate' method for larger dimensions. The default planner > method is 'hybrid'. > > METHOD = FFTW('planner') returns the current planner method. > > STR = FFTW('wisdom') returns the FFTW library's internal wisdom database > as a string. The string can be saved and then later reused in a > subsequent MATLAB session using the next syntax. > > FFTW('wisdom',STR) loads FFTW wisdom, represented as a string, into the > FFTW library's internal wisdom database. FFTW('wisdom','') or > FFTW('wisdom',[]) clears the internal wisdom database. > > For more information about the FFTW library, seehttp://www.fftw.org. > > See also fft, fft2, fftn, ifft, ifft2, ifftn, fftshift. > > Reference page in Help browser > doc fftw
Reply by Vista June 2, 20072007-06-02
Hi all,

Matlab command "fftw" supposedly should return something, as described in 
the following help document. But when I tried these command examples, 
nothing happened, i.e. "fftw" returned nothing.

What might be the problem?

Thanks

------------------------------------------------------------------------------------------

>> help fftw
FFTW Interface to FFTW library run-time algorithm tuning control. The MATLAB functions FFT, IFFT, FFT2, IFFT2, FFTN, and IFFTN functions use a library called FFTW. The FFTW library has the ability to experimentally determine the quickest computational method to compute the FFT of a particular size and dimensionality. The FFTW function provides an interface to this run-time algorithm tuning. FFTW('planner', METHOD) sets the FFTW library planner method used for subsequent calls to FFT, IFFT, FFT2, IFFT2, FFTN, and IFFTN. METHOD can be one of these strings: 'estimate', 'measure', 'patient', and 'exhaustive', or 'hybrid'. If the planner method is 'estimate', then the FFTW library chooses algorithms based on a quick heuristic. The resulting algorithms are sometimes suboptimal. If you specify 'measure', the FFTW library will experiment with many different algorithms to compute an FFT of a given size. The library caches the result in an internal "wisdom" database so that it can reused the next time an FFT of the same size is computed. Methods 'patient' and 'exhaustive' are similar to 'measure' except that they take much longer. If the planner method is 'hybrid', then MATLAB uses the 'measure' method for FFT dimensions of 8192 or smaller, and it uses the 'estimate' method for larger dimensions. The default planner method is 'hybrid'. METHOD = FFTW('planner') returns the current planner method. STR = FFTW('wisdom') returns the FFTW library's internal wisdom database as a string. The string can be saved and then later reused in a subsequent MATLAB session using the next syntax. FFTW('wisdom',STR) loads FFTW wisdom, represented as a string, into the FFTW library's internal wisdom database. FFTW('wisdom','') or FFTW('wisdom',[]) clears the internal wisdom database. For more information about the FFTW library, see http://www.fftw.org. See also fft, fft2, fftn, ifft, ifft2, ifftn, fftshift. Reference page in Help browser doc fftw