H5Part development and discussion

[Andreas Adelmann <andreas.adelmann AT psi.ch>]

Hi Mark ok now I understand.

In case of a stencil based computation with a very anisotropic computation 
domain I can think of such cases. So we probable want to keep this feature
but maybe have a configure option to ride the more easy way; i.e. all the 
dimensions have the same number of ghost nodes. This just in case of you
very well observed problem with O(1E6) cores.

What do you think ?

Best Amdreas 



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Dr. sc. math. Andreas (Andy) Adelmann
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On 14.07.2010, at 00:46, Mark Howison wrote:

> Hi Andreas,
> 
> It means you can have different depths of ghost cells on different
> sides of the 3D block. So the top might have +1 ghost cells, but the
> sides +2, etc. Adjacent blocks with ghost zones also overlap, and it
> is fairly complicated to "reduce" these into non-overlapping regions.
> Right now we handle the most general case, where we don't require any
> adjacency information from the user. There is an MPI_Allgather where
> each processor gets a copy of every other proc's field layout,
> requiring O(n) space. Then an O(n^2) algorithm runs redundantly on
> each proc to compute the reduction,
> 
> It all works and I have never noticed any performance issues
> associated with it, but it may become a scalability problem in the
> future with say O(100K) or O(1M) cores.
> 
> Mark
> 
> On Sat, Jul 10, 2010 at 9:23 AM, Andreas Adelmann
> <andreas.adelmann AT psi.ch> wrote:
>> 
>>>> Do we need to support arbitrary ghost zones?
>> 
>> 
>> Sorry I was maybe not following closely: what are rbitrary ghost zones 
>> w.r.t. H5Block?
>> 
>> AA