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[H5part] Re: H5Block and ghost zones

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  • From: Mark Howison <MHowison AT>
  • To: Achim Gsell <achim.gsell AT>
  • Cc: h5part AT
  • Subject: [H5part] Re: H5Block and ghost zones
  • Date: Fri, 9 Jul 2010 08:38:16 -0700
  • List-archive: <>
  • List-id: H5Part development and discussion <>

Hi Achim, you are right that it isn't a huge amount of memory (there
are actually 2 * 6 * nprocs because it stores both a "user" and
"dissolved" layout), so I will just leave it as is for now. Mark

On Fri, Jul 9, 2010 at 7:01 AM, Achim Gsell <achim.gsell AT> wrote:
> Hi Mark
> On Jul 8, 2010, at 5:54 PM, Mark Howison wrote:
>> I'm still working through the H5Block code, and I wanted to find out
>> more about the original design decisions for handling arbitrary ghost
>> zones, which introduces alot of complexity in "dissolving" them. I
>> don't see an easy way to get around the O(n) space required in the
>> H5Block file struct to store every proc's field layout for use in the
>> ghost zone routines.
> I implemented arbitrary ghost zone on request of LBNL ... But is the O(n)
> space required really an issue? The layout occupies
> 6*sizeof(h5_int64_t)*nprocs bytes per process. With 64k cores it's just 3MB
> (or 0.0022% of the available memory we have on Franklin/core).
>> Do we need to support arbitrary ghost zones?
> Good question, actually I don't know. As far as I know, we don't need them
> at PSI.
> Achim

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