Re: [boost] Re: uBLAS and expression templates

From: David Abrahams (david.abrahams_at_[hidden])
Date: 2002-06-30 08:49:52

From: "Benedikt Weber" <weber_at_[hidden]>

> > The problems you are seeing are not intrinsic to expression templates.
>
> I fully agree. I was talking about the way expression templates are used
in
> uBLAS, not in general about expression templates. In uBLAS they are used
to
> avoid temporary vector an matrix variables, which is a performance
> improvement only in certain cases while in other cases it is a
degradation.

Sorry, I should have been more clear:

    The problems you are seeing are not due to the avoidance of
temporaries.

> In many cases saving temporaries is crucial to avoid unnecessary
> recalculation of subexpressions. As far as I understand, expression
> templates give you the possibility to perform the evaluation in a way
> different from what they would normally be evaluated, so you can use your
> own optimization strategy. (They could possibly even be used to perform
> blocked evaluation of matrix products?).

Yes.