[mpiwg-tools] reset a stopped pvar

Kathryn Mohror kathryn at llnl.gov
Wed Sep 18 22:33:33 CDT 2013

Hi Junchao,

>   What is the right behavior when resetting a stopped pvar? The standard says setting to its starting value.
>   For counters, timers etc, setting them to zero sounds reasonable.
>   But for a watermark, setting it to "the current utilization level" looks weird. It implies that a value caught during the stopped period can affect its future value when the pvar is re-started.
>   Probably, we should reset a stopped watermark to a state as if it has never been started.
>   Any comments?  Thanks

Hmm. It makes sense to me, but I'll let others chime in if they disagree. I think that the moment you start the watermark variable, you want to know what the "mark" is, so it would be the value of current utilization. So even if a higher (or lower) value is caught during the stopped period (which it shouldn't be, because variables aren't supposed to be updated when stopped), it will be set to the current utilization value when started. I interpret this as being able to measure the watermark during different epochs of the program execution. Every time you start the variable, it's a fresh epoch and you want to know what the watermark was during that epoch.

However, I can see how this isn't clear as it could be -- I'll try to see what we can do to clarify it in the text.

Thanks again for taking the time to give us this feedback.


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

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