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Date: Thu, 11 Aug 2011 10:55:40 +0200
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Subject: Re: [math] Read-only RealVector
From: =?ISO-8859-1?Q?S=E9bastien_Brisard?= <sebastien.brisard@m4x.org>
To: Commons Developers List <dev@commons.apache.org>, aploese@gmx.de
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2011/8/11 Arne Ploese <aploese@gmx.de>:
> So you not only want to observe the result, but you want a read only
> RealVector.
>
That's right. I'm sorry, my first message was not clear, especially if
you did not follow the thread on iterative solvers.
I want to observe the *solver*, and the current state of the solver is
a *RealVector*, which should by no means be modified by the observer.
The safest way to do that would be for the solver to have a method
like
public RealVector getCurrentSolution(){
    return x.copy();
}
but that takes both time and memory. So I was thinking of something more like
public RealVector getCurrentSolution(){
    return new ReadOnlyRealVector(x);
}
which takes virtually no additional memory (and presumably very little
time). The two advantages of this approach are
* it does not jeopardize the whole hierarchy tree, since you do not
have to create a new interface,
* it is quite general, and could be adopted for any base object (not
only RealVector).
The downside is that some methods throw exceptions, which might be
deemed dirty. I don't really know.
S

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