[Dune] [Dune-Commit] dune-common r5882 - trunk/dune/common

[Carsten Gräser]

Hi Oliver,

> How about the following compromise:  We add a new allocator
> static_allocator to dune-common.  This allocator would be standard-
> compliant, similar to array_allocator, but actually contain the
> memory it manages.  You could then write something like (not tested)
> 
> typedef Dune::static_allocator<int,10> MyAllocator;
> MyAllocator allocator;
> std::{vector|set|map|whatever}<int,MyAllocator>(allocator);
but list/set/map might (and will in general) allocate
mulitple independent memory fractions. So you can not
use the static_allocator despite you know that the container
will allocate a fixed number (of unknown size) at once.
So one will hardly use this with anything else then vector.
> 
> This is bit simpler than the gnu array_allocator.  You could then
> implement ReservedVector using this allocator, much like Carsten
> suggested.  This would be a very short file, then.
That would be much nicer, however you still waste
memory with the 'pointer to storage' and 'capacity'
members of std::vector.

Regards
Carsten

> 
> Yrs,
> Oliver
> 
> 
>> As you said, you allocate your memory somewhere else. I want something
>> with the memory inside. Actually your vector doesn't allocate memory
>> at all.it is only a view on an other array.
>>
>> I give you two use cases and perhaps you can tell me how it should
>> work.
>>
>> 1) write something like this:
>>    
>>    std::vector< ReservedVector<int,4> > vec;
>>    for (int i=0; i<n; i++)
>>      vec.push_back(ReservedVector<int,4>);
>>
>>    and assume that the number of elements does vary. How to handle
>>    dynmic memory memory management with the allocator?
>>
>> 2) you store some stuff in std::vector< ReservedVector<int,4> > and
>>    hand it to the user. Now the user can delete the vector and the
>>    memory is freed. How so you handle memory-ownership with the
>>    allocator?
>>
>> Perhaps I just don't get it, but I still think that the two approaches
>> are substatially different.
>>
>> Christian
>>   
> 
> 


-- 
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Carsten Gräser           | phone: +49-30 / 838-75349
Freie Universität Berlin | fax  : +49-30 / 838-54977
Institut für Mathematik  | email: graeser at math.fu-berlin.de
Arnimallee 6             |
14195 Berlin, Germany    | URL  : http://page.mi.fu-berlin.de/graeser
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