[MITgcm-support] changing the number of tiles

[Jean-Michel Campin]

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
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> >>>UCSD-0213                              e-mail: pcessi at ucsd.edu
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> >>>USA                      Web:  http://www-pord.ucsd.edu/~pcessi
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