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- To: Eigen <eigen@xxxxxxxxxxxxxxxxxxx>
- Subject: Re: [eigen] nesting
- From: Hauke Heibel <hauke.heibel@xxxxxxxxxxxxxx>
- Date: Thu, 4 Feb 2010 16:01:21 +0100
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Well, specializing the product is a bad idea. Actually, we need to
deduce expressions that have products nested (or heavy weight objects
in general), those must then be nested by reference in order to
On Thu, Feb 4, 2010 at 2:35 PM, Hauke Heibel
> While looking into the "performance degradation" issue from the forum
> I found out that it is due to temporaries - as Benoit already guessed.
> I am a little bit afraid, that what I once proposed, namely copying
> expressions by value, is now backfiring. The reason is that initially
> I assumed expressions to be tiny little objects with close to no copy
> costs. The issue is related to those expressions holding temporaries.
> Copying them (e.g. a product expression) means copying all the data
> including the temporary and that will happen as many times as we nest
> The only solution I can think about at the moment is the
> specialization of ei_nested for those types and to go back to nesting
> by reference for these heavy weight guys.
> - Hauke