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- To: eigen@xxxxxxxxxxxxxxxxxxx
- Subject: Re: [eigen] patch for tridiagonal matrices in eigen
- From: "Mauro Iazzi" <mauro.iazzi@xxxxxxxxx>
- Date: Fri, 9 Jan 2009 01:35:17 +0100
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2009/1/8 Benoit Jacob <jacob.benoit.1@xxxxxxxxx>:
> Hi Mauro,
>
> 2009/1/8 Mauro Iazzi <mauro.iazzi@xxxxxxxxx>:
>> Hi, sorry for replying so late.
>
> No worry at all since we're in the rush to release 2.0 we don't have
> much time at the moment for thinking about this either...
>
> I'll study carefully your mail later, when I have time; for now I just
> want to address this quick point:
>
>> 2008/12/30 Benoit Jacob <jacob.benoit.1@xxxxxxxxx>:
>>>
>>> An expression class MyExpression is a bad idea whenever the
>>> MyExpression::coeff() method is slow and in practice it can be
>>> bypassed when implementing actual algorithms.
>>>
>>
>> It's a perfect criterion. However, when something else than an
>> expression is used, memory may be wasted. This is quite a concern with
>> me: a single matrix storage may be the few hundred megs that exceed my
>> memory and start using swap. I have no obvious solutions.
>
> When I said that we should avoid expressions, I didn't mean that we
> should instead represent as a plain old n*n matrix, storing the
> coefficients!
Sorry, I expressed myself badly. I agree that a diagonal matrix should
have its own storage. That comment was about the return types of
operations on diagonal matrices.
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