Adding Martin's comment since he can't post currently. BTW, I could not understand why a pvar may be writable (i.e., not readonly) from the user? Could someone give me an example. You may want to reset the variable to its starting value so that you can measure it during a specific time period. I can't think of an example off the top of my head for using pvar_write on a variable. (Maybe setting to 0?) If I remember right, we included it for generality. If you don't want to allow a tool to write to a variable, you can just return MPI_T_ERR_PVAR_NO_WRITE. Actually, high watermarks could be a great example here: it would actually be interesting to measure the high watermark of resources like UMQ between two MPI calls. For this you would have to reset (i.e., write) the counter after every MPI call and then you can just read it before every call. The counter could still be continuous, though. Martin Kathryn On Fri, Aug 30, 2013 at 5:11 PM, Mohror, Kathryn <[email protected]<mailto:[email protected]>> wrote: 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" <[email protected]<mailto:[email protected]>> 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 _______________________________________________ mpiwg-tools mailing list [email protected]<mailto:[email protected]> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpiwg-tools ______________________________________________________________ Kathryn Mohror, [email protected]<mailto:[email protected]>, http://people.llnl.gov/mohror1 CASC @ Lawrence Livermore National Laboratory, Livermore, CA, USA _______________________________________________ mpiwg-tools mailing list [email protected]<mailto:[email protected]> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpiwg-tools ______________________________________________________________ Kathryn Mohror, [email protected]<mailto:[email protected]>, http://people.llnl.gov/mohror1 CASC @ Lawrence Livermore National Laboratory, Livermore, CA, USA ______________________________________________________________ Kathryn Mohror, [email protected]<mailto:[email protected]>, http://people.llnl.gov/mohror1 CASC @ Lawrence Livermore National Laboratory, Livermore, CA, USA _______________________________________________ mpiwg-tools mailing list [email protected]<mailto:[email protected]> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpiwg-tools ______________________________________________________________ Kathryn Mohror, [email protected]<mailto:[email protected]>, http://people.llnl.gov/mohror1 CASC @ Lawrence Livermore National Laboratory, Livermore, CA, USA