[MITgcm-support] changing the number of tiles

[Paola Cessi]

Hi Jean-Michel, is the step of reassembling the pickup files into a single 
file necessary? I am asking because I cannot do it in Matlab, given the 
size of my files. Do you have an alternative suggestion that is not as 
memory intensive? Thanks,

paola

On Wed, 1 Mar 2006, Jean-Michel Campin wrote:

> Hi Paola,
>
> The thing that I do generally, in this case, is to read
> all the tile-files (in matlab, with rdmds), and then
> I just write the output from rdmds to a binary file:
>
> namfil='pickup.0000003200';
> va=rdmds(namfil);
> wrfile=[namfil,'.data'];
> fid=fopen(wrfile,'w','b');
> fwrite(fid,va,'real*8');
> fclose(fid);
>
> And there is no problem for the model to restart from a unique file,
> i.e. a "global" file that contains all the tiles, whatever the
> new domain decomposition is.
>
> Jean-Michel
>
> On Wed, Mar 01, 2006 at 07:46:46PM -0500, Baylor Fox-Kemper wrote:
>> No interpickups isn't necessary if there is no interpolation or
>> coarsening, but it will work in that case, too.
>>
>> What Ed is suggesting (I think) doesn't require netcdf.  However,
>> someone not using netcdf should spell out exactly how this is to be
>> done.  I think usually one needs to keep the number of tiles fixed,
>> while changing the number of processors.  However, this process
>> seemed messy to me, so that's why I wrote interpickups in the first
>> place.
>>
>> Will someone please explain how to do retiling, or at pickup
>> conversions (without cubed sphere complications is fine) in the
>> pickups for posterity?
>>   -Baylor
>>
>>
>> On Mar 1, 2006, at 5:49 PM, Paola Cessi wrote:
>>
>>> Is interpickups.m necessary if the number of gridpoints is the
>>> same, and thus no interpolation is needed, but the tiling changes?
>>> paola
>>>
>>> On Wed, 1 Mar 2006, Baylor Fox-Kemper wrote:
>>>
>>>> Hi Paola,
>>>> There is a little program: utils/matlab/interpickups.m, that I
>>>> wrote a while back (and I think works with the present version of
>>>> the code).  It takes a bunch of mnc input pickup files with one
>>>> tiling and a bunch of mnc output pickup files with a different
>>>> tiling, and interpolates between them in a simple way.  This way
>>>> you can coarsen or fine-grain a set of pickup files to restart
>>>> with a different tiling or even a different resolution.  If the
>>>> number of gridpoints in the input and outputs is the same, it
>>>> shouldn't change the data at all, it should just copy it
>>>> appropriately from the input files to the outputs.
>>>> The easy way to get the output pickups is to set up the model
>>>> with the new gridding and run for one timestep outputting a
>>>> pickup.  The routine will then overwrite the data in the files
>>>> with the interpolated data from the set of input files.
>>>> Cheers,
>>>>   -Baylor
>>>>
>>>>
>>>>
>>>> On Mar 1, 2006, at 2:47 PM, Paola Cessi wrote:
>>>>
>>>>> Is it possible to restart a computation with 4*N tiles, using the
>>>>> pickup files generated with N tiles, while keeping Nx and Ny
>>>>> fixed? In other words, is it possible to change nPx and nPy in a
>>>>> restart run, while keeping Nx and Ny the same? (without using
>>>>> netcdf)
>>>>> paola
>>>>> --------------------------------------------------------------------
>>>>> -----
>>>>> Paola Cessi                            Tel: +1 858 534 0622
>>>>> Scripps Institution of Oceanography    Fax: +1 858 534 8045
>>>>> 9500 Gilman Drive
>>>>> UCSD-0213                              e-mail: pcessi at ucsd.edu
>>>>> La Jolla, CA 92093-0213
>>>>> USA                      Web:  http://www-pord.ucsd.edu/~pcessi
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>>>>
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