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From Luc Maisonobe <Luc.Maison...@free.fr>
Subject Re: [math] Read-only RealVector
Date Thu, 11 Aug 2011 09:32:43 GMT
Le 11/08/2011 10:55, Sébastien Brisard a écrit :
> 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.

Well, in fact I would very much like to have immutable vectors too. 
Immutability is really a way to simplify implementations. Surprisingly 
it sometimes also decrease time and memory consumption, because 
defensive copies littering user code can be avoided.

Jeopardizing the hierarchy tree is not a problem IMHO.

Luc

> S
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