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From Gilles Sadowski <>
Subject Re: [Math] Old to new API ("MultivariateDifferentiable(Vector)Function")
Date Sat, 01 Dec 2012 18:37:29 GMT
On Sat, Dec 01, 2012 at 09:59:37AM -0800, Ted Dunning wrote:
> Correctness isn't that hard to get.  You just need to add a bitmap for
> exceptional values in all matrices.  This bitmap can be accessed by sparse
> operations so that the iteration is across the union of non-zero elements
> in the sparse vector/matrix and exception elements in the operand.
> That fact is, however, that preserving NaN results in these corner cases is
> not normally a huge priority for users.  Deleting all support for sparse
> vectors, on the other hand, is a huge impact on utility of commons math.
>  To my mind deleting hugely useful functionality in the face of a small
> issue is upside down, especially when there is actually a pretty simple fix
> available.

Huge impact? It didn't seem so, since _nobody_ answered a recent poll about
deleting the sparse arrays feature.


P.S. There are other Java libraries which, last time I looked, seem to focus
     much more on the storage flexibility viewpoint than does CM (e.g.

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