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From Gilles Sadowski <gil...@harfang.homelinux.org>
Subject Re: svn commit: r1348721 - in /commons/proper/math/trunk/src: main/java/org/apache/commons/math3/linear/OpenMapRealVector.java test/java/org/apache/commons/math3/linear/SparseRealVectorTest.java
Date Tue, 12 Jun 2012 10:21:10 GMT
Hello.

> > [...]
> > I agree.
> >
> >>
> >> This does not solve the whole issue, however, because if the default
> >> entry is zero, its sign is lost, and {finite value} / {zero} is of
> >> undetermined sign. Any idea regarding this point?
> >
> > I guess that we could also keep a flag for the sign.
> >
> Do you mean that the default value would be +0 or -0, in some zero
> entries would be stored?

I didn't get the end of the sentence.

Anyways, what I meant is indeed to be able to specify that the default zero
is negative (so that "v / zero" has the correct sign).

> Or do you mean to store the sign of each zero
> entry,  which is slightly less efficient than the present
> implementation, but would work OK?

No.

> These signs could be stored in very
> compact form (as bits), as they need only seldom be retrieved.

I strongly prefer a "boolean" unless you can devise a way to perform
calculations that strongly benefit from bit manipulation.

Anyways, let's not try to re-invent the wheel...

Regards,
Gilles

> [...]

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