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From Gilles Sadowski <gil...@harfang.homelinux.org>
Subject Re: [math] Equivalent of Blas DAXPY
Date Thu, 07 Jul 2011 14:14:34 GMT
Hello.

> in Blas, the method DAXPY can lead to very compact code. As far as I know, it
> has no equivalent in RealVector. There are a few method called xxxxToSelf,
> which modify the calling vector, instead of returning a new one, but these are
> restricted to scalars operating on vectors.
> In other words, there are no in-place vector-vector operations.
> Would you think it useful to add at least one method, say
> combineToSelf(double s, double t, RealVector v)
> which would replace the components of this by the components of (s * this + t
> * v). This would be a slight generalization of DAXPY.

You should open an issue on JIRA to keep track of this feature request.
[Not sure about the "combineToSelf" name: "combine" is used in
"FunctionUtils" but not exactly with the same meaning...]

> It would be fairly easy to implement for ArrayRealVector, not sure about
> OpenMapRealVector.

A default implementation would be implemented in "AbstractRealVector",
(where a "SparseEntryIterator" is defined and the method "mapToSelf" is an
example of how it is used).


Thanks,
Gilles

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