[Numpy-discussion] "import numpy" performance

Andrew Dalke dalke@dalkescientific....
Mon Jul 2 17:15:46 CDT 2012


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"

Unless I'm lost in a set of header files?

Cheers,

				Andrew
				dalke@dalkescientific.com




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