[C++-sig] Boost.Python: wrapping classes instead of functions???

[David Roy]

Hi,

I'm facing a very strange behavior that I cannot manage to explane.
I'm currently working on a project of re-implementing Python functions in
C++ in order to improve performance and I'm then creating Python extensions
thanks to Boost.
I implemented quite a heavy function that calculates tangents and binormals
this way:

class GeomUtils
{
private:
    // some functions...
public:
    AddTangentAndBinormals();
}

GeomUtils::AddtangentAndBinormals()
{
    // call some functions...
}

BOOST_PYTHON_MODULE(geom_utils)
{
    class_<GeomUtils>("GeomUtils", init<>())
        .def("AddTangentAndBinormals", &GeomUtils::AddTangentAndBinormals)
        ;
}

This was very successful, decreasing the computation time from 54.0 seconds
to less than 1.0 second.
Then I decided this wasn't worth a class and that I should directly export
the function :

AddTangentAndBinormals()
{
    // call some functions...
}

BOOST_PYTHON_MODULE(geom_utils)
{
    def("AddTangentAndBinormals", &AddTangentAndBinormals);
}

and the profile was back to 54.0 seconds!!!
Please could someone help me understand what's the difference and the
mechanism underlying that?

Thanks
-David
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