Hi Jim, I like that change. On a side note: are we really still calling them "info hints" in this context rather than "info assertions"? Cheers, Dan. On 09/02/2016 15:51, Jim Dinan wrote:

Hi All,

I'm preparing the updated draft of info assertions for a reading in March. Where did we land on an advice regarding tools? Do we want advice (1) to users, that they info keys may impact tools and/or (2) to tools that they should check info?

For instance, we could extend the current advice with the following sentence:

Setting info hints on the predefined communicators \const{MPI\_COMM\_WORLD} and \const{MPI\_COMM\_SELF}may have unintended effects, as changes to these global objects may affect all components of the application, including libraries. The usage of info hints may also impact the effectiveness of tools.

~Jim.

On Fri, Dec 18, 2015 at 5:24 AM, Marc-Andre Hermanns <[email protected] <mailto:[email protected]>> wrote:

Hi Jeff,

> at the moment we don't handle MPI_THREAD_MULTIPLE at all. But we want > to get there ;-) > > > You should vote for endpoints, as this may help you out here, > particularly if users start mapping endpoints 1:1 w/ threads.

That would certainly ease things for us in these situations. Unfortunately endpoints force use to adapt other infrastructure in our measurement system.

> b) Creating a derived datatype on the fly to add tool-level data to > the original payload may induce a large overhead in practically > _every_ send & receive operation and perturb the measurement. > > > You should evaluate this experimentally. I wrote a simple test > (https://github.com/jeffhammond/BigMPI/blob/master/test/perf/typepiggy.c) > and measured 1.5 us per call of overhead to create a datatype. That > is not significant except for very small messages.

Thanks for the pointer. You are right. I should evaluate this further. 1.5us does indeed seem tolerable. I wonder how the influence of the derived datatype is on overall messaging performance, though.

This is also something I should evaluate in the process.

Cheers, Marc-Andre

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