Re: conv2 performance

[Søren Hauberg]

man, 01 03 2010 kl. 09:17 -0500, skrev John Swensen:
> On Feb 28, 2010, at 10:53 AM, John W. Eaton wrote:
> > 
> > 
> > Maybe there is still room for improvement here.  I would happily use a
> > free software library with a GPL-compatible license to implement this
> > function, but I don't know whether one is available.
> > 
> > jwe
> > 
> 
> I have recently been doing a lot of 2D convolutions.  I think the
> fastest method should not involve loops of any kind.  As convolution
> in the time domain (or spatial domain when considering images) is
> multiplication in the frequency domain, the fastest method is to take
> the FFT of both image and kernel, dot-multiply them, then take the
> inverse FFT.

>From what I understand, the downside is that this approach can loose
quite a bit of precision. Here are some of the thoughts by a Matlab
engineer:


http://blogs.mathworks.com/steve/2009/11/03/the-conv-function-and-implementation-tradeoffs/

Soren