Re: [eigen] Optimization for special complex operations

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On Mon, Aug 16, 2010 at 2:34 PM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx> wrote:
2010/8/16 Carlos Becker <carlosbecker@xxxxxxxxx>:
> Hi everyone again. Lately I've been using Eigen with complex numbers to
> calculate things such as calculating the maximum of the real part or
> imaginary part of a certain vector. I suppose that trying to take the real
> part and then use maxCoeff() or minCoeff() would create a possible
> unnecessary temporary.

No, it wouldn't :-)

Ok good, maybe 'temporary' is not exactly what I wanted to say. I mean that maybe there are vectorized ways to do certain stuff and special implementations could be provided for such operations.

> Another thing is to be able to do something like:
> MatrixXf nn,xx;
> xx = nn.colwise().normalized();

Hm. If we start going that route, won't we end up offering every
possible vector operation as colwise() operation?


The biggest reason not to do it now is that it really isn't necessary
to release Eigen 3.0 .... ;-)

Yes I understand. I think vector-wise operations could be very important, but they would probably require a bit of discussion before implementing them (ie: should we keep .colwise(), should we use .vectorwise(), in the case some names for the reductions and vector-wise operations are the same).. I believe these kind of operations would be very useful since many times a set of vectors is stored in a matrix, so this way the user could benefit from extra performance.

I could try some prototypes to see if I can make it work. I designing something like .vectorwise() could be fine.


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