Question for the HP guys....

10082017, 11:37 PM
Post: #1




Question for the HP guys....
I remember from back in my supercomputer days, the FFT algorithm was pretty important in the field I worked in, and there were generally 2 ways to implement it. The first used bitreverse and radix2 transform, while the second used digitreverse and radix4 transform. Radix4 was quite a bit faster in implementation, so what I'm wondering is which is the version of the FFT function on the HP Prime, radix2 or radix4 ?????????
Thanks Donald 

10092017, 12:03 AM
Post: #2




RE: Question for the HP guys....
https://wwwfourier.ujfgrenoble.fr/~par...mpile.html
You'll be able to find it just as fast I think. Download the source, search for "fft" and you'll probably find it. Bernard might chime in. TW Although I work for the HP calculator group, the views and opinions I post here are my own. 

10092017, 12:30 AM
Post: #3




RE: Question for the HP guys....
(10092017 12:03 AM)Tim Wessman Wrote: Download the source, search for "fft" and you'll probably find it. Bernard might chime in. https://wwwfourier.ujfgrenoble.fr/~par...modpoly.cc Around line 3171: Code: // Fast Fourier Transform, f the poly sum_{j<n} f_j x^j, Ceci n'est pas une signature. 

10092017, 04:25 AM
Post: #4




RE: Question for the HP guys....
I looked through the source code and from what I can tell, in maple.cc, if HP uses gcc and libgsl (Gnu Scientific Library), then they call the radix2 transform function.
Anyway, radix 4 speed increases are only significant when a large number of data elements are being used and since we are talking about a calculator, it's doubtful if large numbers of data elements are going to be used in fft's. Thus the advantage of a radix4 would be minimal in any case. Good 'nuff... :) Thx Donald 

10102017, 09:09 AM
Post: #5




RE: Question for the HP guys....
The GSL is not active when giac is compiled for the Prime.
There are two main FFT implementations, one for complex<double> data, and one for modular integers. The first one has prototype Code: void fft(std::complex<double> * f,int n,const std::complex<double> * w,int m,complex< double> * t) 

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