[Python-Dev] Speed up function calls (original) (raw)
Neal Norwitz nnorwitz at gmail.com
Sun Jan 23 19:39:42 CET 2005
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I added a patch to SF: http://python.org/sf/1107887
I would like feedback on whether the approach is desirable.
The patch adds a new method type (flags) METH_ARGS that is used in PyMethodDef. METH_ARGS means the min and max # of arguments are specified in the PyMethodDef by adding 2 new fields. This information can be used in ceval to call the method. No tuple packing/unpacking is required since the C stack is used.
The benefits are:
- faster function calls
- simplify function call machinery by removing METH_NOARGS, METH_O, and possibly METH_VARARGS
- more introspection info for C functions (ie, min/max arg count) (not implemented)
The drawbacks are:
- the defn of the MethodDef (# args) is separate from the function defn
- potentially more error prone to write C methods???
I've measured between 13-22% speed improvement (debug build on Operton) when doing simple tests like:
./python ./Lib/timeit.py -v 'pow(3, 5)'I think the difference tends to be fairly constant at about .3 usec per loop.
Here's a portion of the patch to show the difference between conventions:
-builtin_filter(PyObject *self, PyObject *args) +builtin_filter(PyObject *self, PyObject *func, PyObject *seq) {
PyObject *func, *seq, *result, *it, *arg;
PyObject *result, *it, *arg; int len; /* guess for result list size */ register int j;
if (!PyArg_UnpackTuple(args, "filter", 2, 2, &func, &seq))return NULL;
the are no other changes between METH_O and METH_ARGS
{"abs", builtin_abs, METH_O, abs_doc},
{"abs", builtin_abs, METH_ARGS, abs_doc, 1, 1},
{"filter", builtin_filter, METH_VARARGS, filter_doc},
{"filter", builtin_filter, METH_ARGS, filter_doc, 2, 2},
Neal
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