Re: [eigen] FFT for Eigen

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This is probably not a good idea. I believe that they should be stored
in the interleaved format. I'll be happy to pitch in with SSE2/3
intrinsics code for complex multiplication, division if neccessary. I
think we should go the standard way as many other libraries and
std::complex use it.

So far, on this discussion, the only reason for not using the
interleaved format that I have seen is that it is tricky to multiply
using that. Is there any other reason?

IMHO, we shouldn't lose compatibility with ~90% of other complex
libraries/formats just to simplify multiplication.

On Tue, May 19, 2009 at 5:49 AM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx> wrote:
> I can believe that this is probably a very efficient storage scheme.
> We could offer this as an option if really it's not too hard to
> implement (i didn't start thinking about this).
> The default should remain the current for many reasons, but as an
> option why not.
> Cheers,
> Benoit
> 2009/5/19 Márton Danóczy <marton78@xxxxxxxxx>:
>>> I concur: I don't think that it would be very useful to have complex
>>> matrices with the real and imaginary parts stored separately. Most
>>> operations -- and the more costly ones -- would run slower in such a
>>> scheme. The basic issue here is memory locality.
>> What about storing them packet by packet? That is, in case of floats,
>> four real parts followed by four imaginary parts. That would not be
>> too hard to implement and vectorization of component-wise operations
>> would be trivial. And I think even FFTW can handle that using the guru
>> interface, by setting up a split fft plan with a stride of
>> 2*packetsize.
>> Marton

Rohit Garg

Senior Undergraduate
Department of Physics
Indian Institute of Technology

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