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https://issues.apache.org/jira/browse/MATH-613?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13063456#comment-13063456
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Sébastien Brisard commented on MATH-613:
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I have no experience whatsoever with Colt, but I taking the element by element
max of two vectors might be an example of use (maybe). As for me, I'm happy
with the linear case. And I like combine/combineToSelf.
> Equivalent of Blas DAXPY
> ------------------------
>
> Key: MATH-613
> URL: https://issues.apache.org/jira/browse/MATH-613
> Project: Commons Math
> Issue Type: New Feature
> Affects Versions: 3.0
> Reporter: Sébastien Brisard
> Priority: Minor
> Labels: linear, vector
>
> In Blas, the method {{DAXPY}} computes an in-place linear combination of two
> vectors. More precisely, a call to {{DAXPY(a, x, y)}} updates vector {{y}}
> with the value of {{a * x + y}}. This can lead to very compact code, which I
> feel the need for in Commons-Math. However, DAXPY also has its limitations.
> For example, it cannot perform the other combination {{y <- x + a * y}}.
> I think it would be useful that {{RealVector}} had a method for computing {{a
> * this + b * y}}, and storing the result in {{this}}. In the spirit of the
> {{mapToSelf}} method, I propose to create two new methods in {{Interface
> RealVector}}
> {noformat}RealVector map(BivariateRealFunction f, RealVector y){noformat}
> and
> {noformat}RealVector mapToSelf(BivariateRealFunction f, RealVector
> y){noformat}
> The former would return a new vector {{v}} such that
> {noformat}v[i] <- f(this[i], y[i])}}{noformat}
> and the latter would update {{this}},
> {noformat}this[i] <- f(this[i], y[i]){noformat}
> Emulating {{DAXPY}} would then simply be a matter of implementing the
> appropriate bivariate function.
> While we are at it, how about
> {noformat}RealVector map(TrivariateRealFunction f, RealVector y, RealVector
> z){noformat}
> {noformat}RealVector mapToSelf(TrivariateRealFunction f, RealVector y,
> RealVector z){noformat}
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