[HPGMG Forum] hydra IMC

Mark Adams mfadams at lbl.gov
Tue Jun 10 20:06:05 UTC 2014

Thanks Ian,

I guess there is no MCB data.  I've heard mention if the importance of
radiation and neutron transport codes.

It looks like UMT 2013 is a transport code and HPGMG matches it pretty well
with this data.  For what that is worth.

Thanks again,

On Tue, Jun 10, 2014 at 3:12 PM, Karlin, Ian <karlin1 at llnl.gov> wrote:

>  Hi Mark,
>  I'm adding Steve Langer the first author of the paper in case he has
> anything to add as he's been more focused on trying to track down latency
> issues.
>  Our results point to, but do not defiantly show the latency is the
> likely culprit for both the IMC and Laser packages.  This is due to the low
> IPC, low BW utilization and high number of L2 misses per line fetched from
> memory.  A number above 1 means that multiple reads occurred to a line in
> quick succession, but it was not prefetched.  Below 1 means that many lines
> were successfully prefetched.  We need to either look on other systems with
> better latency measurement capabilities or find the needle in a haystack
> (or combination thereof) of performance counters that gets us more
> definitive latency data.
>  Note MCB does something, but not a lot more than IMC in Hydra.  Likely
> this due to a smaller problem size that is run for MCB it has a higher
> cache hit rate so latency is not as large of a factor though MCB is often
> latency bound.  We didn't think too hard about MCB though for this work.
>  So to answer your question.  Yes there are other metrics worth thinking
> about and latency is one of them.  We're not sure how to capture all of
> them well, which is why we left the data off the kivet plots, but included
> hydra imc to show that we were missing something.
>  Ian
>   From: Mark Adams <mfadams at lbl.gov>
> Date: Tuesday, June 10, 2014 8:32 AM
> To: WCI LLNL <karlin1 at llnl.gov>
> Cc: Theodore Omtzigt <theo at stillwater-sc.com>, HPGMG Forum <
> hpgmg-forum at hpgmg.org>, "Still, Bert" <still1 at llnl.gov>
> Subject: hydra IMC
>   Ian,
>  I see you are an author on a paper about Hydra (IMC).  In our modeling
> efforts we are concerned about MC, transport, etc. that might be poorly
> represented with HPGMG.  I would imagine that these methods use lots of
> streaming data but 'Hydra IMC' data on the spreadsheet does NOTHING!  Do
> you have any thoughts on this?  Is there a metric that you are not
> measuring here that should be and that we should think about?
>  Mark
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