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====== Measuring performance ======
In general, to obtain useful information from binaries, certain compile flags should be used.


===== Perf =====
For using perf, one should compile OOFEM with the flag ''-fno-omit-frame-pointer''
First record a session using

''perf record -g ./oofem -f myinputfile.in''

which will generate a perf.data file.

Then you can visualize the results in several ways. A good, simple to understand method is to use [[http://code.google.com/p/jrfonseca/wiki/Gprof2Dot|Gprof2Dot]] to generate a complete callgraph:

''perf script | ./gprof2dot.py -f perf | dot -Tsvg  -o output.svg''

Perf has very small overhead, but only does statistical sampling.
===== Callgrind =====
Callgrind is a tool in valgrind, and should only be used on medium. This has a huge overhead, so expect OOFEM to run over a hundred times slower through valgrind.
Simply run

''valgrind --tool=callgrind ./oofem -f myinputfile.in''

and you will produce a new file named ''callgrind.out.123456'' where the numbers at the end are randomized.
Open this file in Kcachegrind to visualize the results.