[firedrake] Hardware counters for Firedrake

[Justin Chang]

Lawrence, I will give this a try, thanks.

On Thu, Jul 9, 2015 at 7:41 AM, Lawrence Mitchell <
lawrence.mitchell at imperial.ac.uk> wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Hi Justin,
>
> On 09/07/15 09:18, Justin Chang wrote:
> > Hi everyone,
> >
> > I am very new to Firedrake, i recently switched over from FEniCS,
> > so pardon me if this is a newbie question.
> >
> > If I wanted to run hardware performance counters from PAPI to
> > diagnose my firedrake application how would I go about doing this?
> > In FEniCS, my application was written in C++ and I included the
> > PAPI directives and libraries in the CMakefile. With this I was
> > able to specify where in the source code I wanted to start and stop
> > the counters.
> >
> > Is there a way to somehow replicate this if my code is written
> > using Firedrake?
>
> This is somewhat tricky, since we generate all code to spin over the
> mesh for assembly at runtime, and the calls into PETSc happen purely
> from petsc4py.  There are two approaches which will have slightly
> different measurement characteristics:
>
>
> 1. Measure from Python
>
> I wrote some bindings for the high-level PAPI API that are callable
> from Python.  They seem to be broadly functional.  See
>
> https://github.com/firedrakeproject/PyPAPI
>
> To use these you do:
>
> import pypapi
> import numpy as np
>
> events = np.asarray([pypapi.Event.TOT_CYC], dtype=pypapi.EventType)
>
> counts = np.zeros(1, dtype=pypapi.CountType)
>
> pypapi.start_counters(events)
> # Do your computation (for example, assembling an operator)
> ...
> pypapi.stop_counters(counts)
>
> # counts now contains the number of cycles elapsed between start
> # and stop
>
> Note that this approach includes cycle/flop counts and timings for the
> full stack of computation: that is, it counts work in the python
> interpreter as well as the low-level C that does the assembly loop.
> In some sense, this is the fairest thing to report (since that's the
> work your code is actually doing).
>
> 2. Measure in the generated code
>
> This gives you finer-grained control over where you want to actually
> count things, and gets you much closer to the metal.  However, it's
> (much) trickier to do.
>
> Firedrake defers to PyOP2 to do computation on meshes, and it is PyOP2
> which generates the code to do this.  If you want to insert PAPI calls
> here there are two things to consider:
>
> 1. Where exactly you want to measure.  I guess you'll want to measure
> around a complete assembly over the mesh, rather than the execution of
> an individual kernel.
>
> 2. How to get the information back out again so you can inspect it.
>
> As to the former, I think it should be possible to extend the code
> generation to optionally insert the correct PAPI calls.  Returning the
> information is also probably not too difficult, we can stuff the
> results in a Python dict (or similar) that you can then query from PyOP2.
>
>
> My recommendation is to try the pure Python approach first.  If you
> want finer-grained control, we can provide guidance and/or help on how
> to best do that.
>
> Cheers,
>
> Lawrence
>
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1
>
> iQEcBAEBAgAGBQJVnmvxAAoJECOc1kQ8PEYvSqYH/iL2eE6Vz5OF9yG8yIFRAghN
> h6VOYZ5GgA420U8k6sjP1fBdHwidAUV8gtVLhBuj7UskTWf/HwSVvfUwf1KbPUie
> fAzopYfuDXVolR3uYnUX5GDYDin1gkCCRRbOrk0wU98bSOyaRmcgmg0l3aDp4VTO
> zHruPKzxyhgqoaWqcq5y7HFTCa3TYPBfdoJ3mu3zK4U8AWKMnuhKq24BEA6pBZfV
> fSf4MvlCMKSmxOFTHYeOuPExmtM3m4y049Me88uxRi0gS3fTb1Yhhuhi9zF9DRXC
> YIt1xKjZ+kudwiII22MA35rlXYjqxtShqMDuPC2HZi3xuIuANEWIGAE9uqhx4aY=
> =HJsh
> -----END PGP SIGNATURE-----
>
> _______________________________________________
> firedrake mailing list
> firedrake at imperial.ac.uk
> https://mailman.ic.ac.uk/mailman/listinfo/firedrake
>
-------------- next part --------------
HTML attachment scrubbed and removed