[dune-fem] Bug in jacobianAll

[Martin Nolte]

Hi Marco,

until all grids are converted, the second variant should actually be the faster 
one. The first one is, of course, more beautiful.

Grid implementations not adapted to the recent changes will return a "const 
Entity &" on dereferencing an iterator. So, if you catch the reference, no extra 
copy needs to be made.

If the grid implementation is already adapted to the interface change, it will 
return an "Entity" on dereferencing an iterator and it has to be copied anyway. 
In this case, there is no difference between the two versions, because "const 
auto &" will also bind to the copy.

Best,

Martin

On 03/09/2015 12:09 PM, Agnese, Marco wrote:
> Hi Martin,
> thank you very much for the detailed explanation.
> I was aware of the copyable entities/intersections change but I hadn't thought about the implications.
>
> Now I am using in my code the range based for which seems a more concise and elegant way to solve this issue.
>
> One final question, performance wise, is better to use
>
> for(const auto entity: space)
>
> or
>
> for(const auto& entity:space) ?
>
> You said that might be some difference for some grid overloading the copy constructor, therefore I assume that the first should be preferred.Am I right?
>
> Thank you very much,
> cheers,
> Marco.
>
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-- 
Dr. Martin Nolte <nolte at mathematik.uni-freiburg.de>

Universität Freiburg                                   phone: +49-761-203-5630
Abteilung für angewandte Mathematik                    fax:   +49-761-203-5632
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