Question about FFTW vs. gwnum?

hangxanh · 2014-10-24, 04:45

Hello everyone.
According to Wikipedia, FFTW is the fastest free FFT library. However, it also goes without saying that gwnum (George Woltman's FFT library) is world-class code. Does anyone know how gwnum compares to FFTW? The FFTW benchmarks webpage does rank it among other programs, but there is no mention of Prime95; the closest thing is Ernst's implementation.

Nevertheless, I'd suspect gwnum to be faster because it uses assembly for its core operations, while FFTW uses C subroutines. If FFTW was faster, then George would have used it already.

After all, I don't think the FFTW folks are wrong when they claim it's the fastest free FFT library because Prime95 isn't technically free software (due to the EFF prize distribution terms).

rogue · 2014-10-24, 13:06

Quote:

Originally Posted by hangxanh

Hello everyone.
According to Wikipedia, FFTW is the fastest free FFT library. However, it also goes without saying that gwnum (George Woltman's FFT library) is world-class code. Does anyone know how gwnum compares to FFTW? The FFTW benchmarks webpage does rank it among other programs, but there is no mention of Prime95; the closest thing is Ernst's implementation.

Nevertheless, I'd suspect gwnum to be faster because it uses assembly for its core operations, while FFTW uses C subroutines. If FFTW was faster, then George would have used it already.

After all, I don't think the FFTW folks are wrong when they claim it's the fastest free FFT library because Prime95 isn't technically free software (due to the EFF prize distribution terms).

There are multiple flavors of FFT. FFTW is a generic library. gwnum is specific, thus it doesn't support all of the FFTs that FFTW can do.

Dubslow · 2014-10-24, 15:48

Additionally, being in C, FFTW is far more portable to any plausible architecture with a C compiler; gwnum is specfically written for, and only runs on, variations of the x86 architecture. (For instance, PowerPC Macs couldn't run gwnum, nor can most modern phones or tablets.)

2014-10-24, 04:45	#1
hangxanh "hang" Oct 2014 ho chi minh city 3 Posts	Question about FFTW vs. gwnum? Hello everyone. According to Wikipedia, FFTW is the fastest free FFT library. However, it also goes without saying that gwnum (George Woltman's FFT library) is world-class code. Does anyone know how gwnum compares to FFTW? The FFTW benchmarks webpage does rank it among other programs, but there is no mention of Prime95; the closest thing is Ernst's implementation. Nevertheless, I'd suspect gwnum to be faster because it uses assembly for its core operations, while FFTW uses C subroutines. If FFTW was faster, then George would have used it already. After all, I don't think the FFTW folks are wrong when they claim it's the fastest free FFT library because Prime95 isn't technically free software (due to the EFF prize distribution terms).

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2014-10-24, 15:48	#3
Dubslow Basketry That Evening! "Bunslow the Bold" Jun 2011 40<A<43 -89<O<-88 3×29×83 Posts	Additionally, being in C, FFTW is far more portable to any plausible architecture with a C compiler; gwnum is specfically written for, and only runs on, variations of the x86 architecture. (For instance, PowerPC Macs couldn't run gwnum, nor can most modern phones or tablets.)