[Carpet] Carpet regridding

[Erik Schnetter]

On Oct 31, 2006, at 20:07:24, Ian Hinder wrote:

> Erik Schnetter wrote:
>> On Oct 30, 2006, at 15:40:40, Ian Hinder wrote:
>>
>>> Erik Schnetter wrote:
>>>> On Oct 28, 2006, at 03:27:57, Ian Hinder wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> When using CarpetRegrid and the coordinates string, and if I say
>>>>> 'regrid_every = 1', then does Carpet actually do any work if  
>>>>> the grid
>>>>> structure from the coordinates string has not changed?  It  
>>>>> definitely
>>>>> says 'Recomposing the grid hierarchy', so it looks like it is  
>>>>> doing
>>>>> work.  If this is the case, would it be easy to add an  
>>>>> optimization so
>>>>> that if the grid structure has not changed nothing is done?
>>>>
>>>> CarpetRegrid just decides the grid structure; the real work is  
>>>> always
>>>> done by Carpet and CarpetLib.  I interpret your idea as a  
>>>> performance
>>>> optimisation.  Old versions of Carpet did not contain these
>>>> optimisations, new versions should be much better in that respect.
>>>>
>>>> The development version of Carpet should contain this  
>>>> optimisation, the
>>>> stable version does not.
>>>
>>> Ah good.  Thanks.  By the stable version now you mean carpet- 
>>> stable-3?
>>
>> Yes, but carpet-stable-2 was probably even worse in that respect.
>
> I am looking at
>
> CarpetRegrid/src/manualcoordinatelist.cc
>
> from the latest development version.  It seems to always return 1 to
> indicate that regridding should occur.  Is Carpet more intelligent
> internally, and realizes that the grid structure has not changed?

Yes; upon regridding, CarpetLib keeps a copy of the old grid  
structure, and then determines which levels did not change, and omit  
the corresponding operations (copying, prolongating, applying  
boundary conditions, etc.).

-erik

-- 
Erik Schnetter <schnetter at cct.lsu.edu>

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