[Numpy-discussion] Evaluating performance of f2py extensions with gprof, why spending time _gfortran_compare_string

Åsmund Hjulstad asmund.hjulstad@gmail....
Tue Aug 24 06:16:09 CDT 2010


2010/8/18 Åsmund Hjulstad <asmund.hjulstad@gmail.com>

>
> I am calling a few functions in a fortran library. All parameters are short
> (longest array of 20 elements), and I do three calls to the fortran library
> pr iteration. According to the python profiler (running the script as %run
> -p in ipython), all time is spent in the python extension.
>
> I built the extension with options  -pg -O , ran a test script, and
> evaluated the output with
>
> gprof <libraryname>.py -b
>
> with the following output:
>
> Flat profile:
>
> Each sample counts as 0.01 seconds.
>   %   cumulative   self              self     total
>  time   seconds   seconds    calls  Ts/call  Ts/call  name
>  41.64      5.03     5.03
> _gfortran_compare_string
>  27.40      8.34     3.31                             rdxhmx_
>


I have found one gotcha in my approach, and that is that I have been
building the extension using distutils. It appears that extra_compile_args
options are not passed to fortran compilers (only c compilers). As a result,
the call graph was missing most of the interesting information. After a
change in GnuFCompiler, I now force distutils to compile fortran codes with
-pg enabled.

Perhaps this should be filed as a feature request?  (distutils compilation
with profiling enabled?, or at least the option of passing additional
arguments to gfortran)

Back to my original problem, though, I'm still struggling. What is calling
_gfortran_compare_string, that still is taking up more than 40% of
processing time?

-----------------------------------------------
                                                 <spontaneous>
[6]     43.1    5.10    0.00                 _gfortran_compare_string [6]
-----------------------------------------------


Any suggestions?
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