Re: [eigen] In-place decompositions; was: UmfPackSupport vs SuperLUSupport: input matrix

[Christoph Hertzberg <chtz@xxxxxxxxxxxxxxxxxxxxxxxx>]

On 16.04.2013 17:50, Gael Guennebaud wrote:
> On Tue, Apr 16, 2013 at 3:49 PM, Christoph Hertzberg
> <chtz@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> > A fixed-size use case I would have is to have a lot of rather small fixed
> > size matrices which are accumulated simultaneously and shall all be
> > decomposed, once the accumulation is done.
>
> damn, I was not expecting use cases for small fixed size matrices, but
> yours is perfectly reasonable. Then there are two approaches, either
> the factorization uses the memory shared by the matrix A, or we create

I just filed a feature request for this:
http://eigen.tuxfamily.org/bz/show_bug.cgi?id=707

API-wise this could be accomplished by declaring the decomposition as
Decomposition<Ref<MatrixXd> >.
On calling compute(mat), it would not copy the matrix, but simply 
re-initialize the internal reference.
I assume the rest of the code can stay as it is -- unless someone also 
wants to store the additional data of the decomposition (like 
permutation matrices) into already allocated memory.

Christoph








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Dipl.-Inf., Dipl.-Math. Christoph Hertzberg
Cartesium 0.049
Universität Bremen
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