Problem on Blue Gene/P

[Wei-keng Liao]

Hi, Julien,

The current release of parallel netcdf 1.0.3 does not support
an array size that has more than 2^32 elements. It is because
of the netCDF header format uses only 32-bit integers. I think
this is most likely your case.

The next release of pnetCDF will support large-size arrays,
i.e. > 2^32 elements. The file format will also have slight
changes (in order to use 64-bit integers for metadata.)

Wei-keng


On Jun 12, 2009, at 7:19 AM, Julien Bodart wrote:

> Hi everybody,
>
> I am doing some CFD on a Blue Gene/P computer (40 thousand cores). I  
> am trying to use parallel Netcdf, as I originally used Netcdf-3  
> format. Everything works fine on small cases(10 millions grid  
> points), but when going to bigger cases (1000 millions grid-points)  
> problems arise. I tried to use the 64 bits flag, which does not  
> improve the matter.
> Actually I am trying to write 64 files whose size is lower than 1GB,  
> using some subcommunicators.
> While it does not create any problems on small cases, bigger cases  
> stop at the ncmpi_enddef call on some files (randomly, even with  
> synchronisation in between), saying that there is a mismatch between  
> dimensions. After many check it does not seems that there is  
> something wrong with the dimensions. I have no idea of how to solve  
> the problem. Did anyone had similar problem? Thanks for your help.
>
> Julien