Created TimeTasks class for coarse-level profiling

[alecjohnson]

I am creating

  utility/TimeTasks.h

implemented in

  utility/diagnostics.cpp

to perform coarse-level self-profiling.

The essential tasks to profile are:

• computing moments
• computing fields
• pushing particles

The time spent in each task is subdivided into

• computation
• communication

This class is conceived of as a singleton.

Statistics are accumulated via calls to start_() and end_() methods at the beginning and end of major procedure calls and at the beginning and end of communication routines such as those found in "communication/ComNodes3D.h". The start() and end() methods call MPI_Wtime().

Detailed behavior regarding accumulation or averaging of statistics across MPI processes and/or cycles of the algorithm is not yet specified.

[murci3lag0]

Isn't this done by profiling tools like Scalasca?

[markidis]

i think it's very useful to have some low-overhead performance measurement directly in iPIC3D. I wouldn't write more code than what Alec implemented. Other tools can be used for more fine-grained performance tracing.

[alecjohnson]

Thanks. Agreed. I wouldn't want to fill the code with
book-keeping calls at the beginning and end of every trivial
function. But I would also like to avoid having to instrument
with full-blown profiling on every platform just to get the
coarsest statistics, which can be accomplished with book-keeping
calls at the beginning and end of a small number of functions.

Alec

On Tue, Jun 04, 2013 at 04:20:11PM -0700, markidis wrote:

i think it's very useful to have some low-overhead performance measurement
directly in iPIC3D. I wouldn't write more code than what Alec implemented.
Other tools can be used for more fine-grained performance tracing.

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[murci3lag0]

Added to master branch.