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From Ted Dunning <>
Subject Re: [Math] Old to new API ("MultivariateDifferentiable(Vector)Function")
Date Sat, 01 Dec 2012 17:59:37 GMT
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

On Sat, Dec 1, 2012 at 8:02 AM, S├ębastien Brisard <
> wrote:

> A few months ago, we started a thread on this issue (on the users ML). It
> got no answers! I am personally not happy with removing the support for
> sparse vectors/matrices, but the truth is we didn't see a way to achieve
> the same degree of correctness as --say-- array based matrices and vectors.
> As far as I am concerned, though, this is still an open question, and if
> you have ideas about these issues, we would be glad to here them!

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