[Numpy-discussion] "import numpy" performance

[Nathaniel Smith]

On Mon, Jul 2, 2012 at 11:15 PM, Andrew Dalke <dalke at dalkescientific.com> wrote:
> On Jul 2, 2012, at 11:38 PM, Fernando Perez wrote:
>> No, that's the wrong thing to test, because it effectively amounts to
>> 'import numpy', sicne the numpy __init__ file is still executed.  As
>> David indicated, you must import multarray.so by itself.
>
> I understand that clarification. However, it does not affect me.
>
> I do "import rdkit.Chem". This is all I really care about.
>
> That imports "rdkit.Chem.rdchem" which is a shared library.
>
> That shared library calls the C function/macro  "import_array", which appears to be:
>
> #define import_array() { if (_import_array() < 0) {PyErr_Print(); PyErr_SetString(PyExc_ImportError, "numpy.core.multiarray failed to import"); } }
>
>
> The _import_array looks to be defined via numpy/core/code_generators/generate_numpy_api.py
> which contains
>
> static int
> _import_array(void)
> {
>   int st;
>   PyObject *numpy = PyImport_ImportModule("numpy.core.multiarray");
>   PyObject *c_api = NULL;
>    ...
>
>
> Thus, I don't see any way that I can import 'multiarray' directly,
> because the underlying C code is the one which imports
> 'numpy.core.multiarray' and by design it is inaccessible to change
> from Python code.
>
> Thus, the correct reference benchmark is "import numpy.core.multiarray"

Oh, I see. I withdraw my comment about how you shouldn't import
numpy.core.multiarray directly, I forgot import_array() does that.

-n