[mpiwg-tools] pvar attribute questions

[Mohror, Kathryn]

Hi Martin and Junchao,

Sorry, I can't respond to the list at the moment (LOFT settings) and I was trying to answer when Kathryn was sending her answer - feel free to repost on the list if it makes sense.

Okay, I'm cc'ing the list so others benefit from your point.

I agree with her interpretation - that was our intention. I agree, though, that probably doesn't make sense and hence I generally don't expect MPI implementations to offer high/low watermarks as non-continnous variables, but that's up to them.

It could make sense though. You could possibly have a non-continuous variable that is the high watermark of some metric (e.g., messages in the unexpected queue) so that you could query it for specific time periods. But, you're right, it's up to the implementation to decide what is offered.

Kathryn

Martin



On Aug 30, 2013, at 11:48 PM, "Mohror, Kathryn" <mohror1 at llnl.gov<mailto:mohror1 at llnl.gov>>
 wrote:

Hi Junchao,

I'm trying to understand MPI3 MPI_T performance variables (pvar).  The standard defines pvar sessions, pvar classes (e.g.,COUNTER, HIGHWATERMARK etc), and continuous pvars, readonly pvars.I was wondering if there is any relevance between these concepts. The standard doesn't say that.

For instance, for a highwatermark pvar, I guess it should be continuous. Otherwise, suppose a pvar session starts this pvar, then stops it, and then restarts it.  How can I keep track of this pvar? Let's say during the live period of the pvar, the high watermark is 50. After the pvar is stopped, it went up to as high as 90 (since it may be alive in other pvar sessions). So, when I restart the pvar, what value should I read?

If a variable is not continuous then its value is not updated when it is stopped. So in your example the value would be 50 in the session that stopped the variable and 90 in any sessions that still had the variable live at the time it reached that value. There's a bit more explanation on page 579 starting at line 21. Does that help?

Kathryn


Thanks
--Junchao Zhang

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Kathryn Mohror, kathryn at llnl.gov<mailto:kathryn at llnl.gov>, http://people.llnl.gov/mohror1
CASC @ Lawrence Livermore National Laboratory, Livermore, CA, USA




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Kathryn Mohror, kathryn at llnl.gov<mailto:kathryn at llnl.gov>, http://people.llnl.gov/mohror1
CASC @ Lawrence Livermore National Laboratory, Livermore, CA, USA




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