Cython calls ExtType.__init__() as Python function

[robertwb]

When subclasses of extension types call the __init__() method of their supertype, Cython generates code that looks up the "__init__" attribute of the instance and then calls it through Python using arg tuple/kwargs. This is because the special __init__() method ("tp_init" slot) uses this call signature.

Cython should recognise calls to this method and at least call it directly.

In the (presumably very common) case that the arguments do not use starargs, a more advanced approach would be to split the __init__() method into an internal plain C-function replacement and a tp_init wrapper, and then call the internal function directly, without doing any tuple packing etc. Not sure if it's worth it, though, as the call is already preceded by an (expensive) object allocation.

Migrated from http://trac.cython.org/ticket/3

[robertwb]

@robertwb changed owner from robertwb to somebody
commented

[robertwb]

@garyfurnish commented

One of the first things I do is make my own c wrappers for creating objects. Even with the expensive new call the savings it noticeable.

[robertwb]

@robertwb changed milestone to wishlist
commented

[robertwb]

scoder changed description from

When subclasses of extension types call the init() method of their supertype, Cython generates code that looks up the "init" attribute of the instance and then calls it through Python using arg tuple/kwargs. This is because the special init() method ("tp_init" slot) uses this call signature.

Cython should recognise calls to this method and at least call it directly.

In the (presumably very common) case that the arguments do not use starargs, a more advanced approach would be to split the init() method into an internal plain C-function replacement and a tp_init wrapper, and then call the internal function directly, without doing any tuple packing etc. Not sure if it's worth it, though, as the call is already preceded by an (expensive) object allocation.

to

When subclasses of extension types call the __init__() method of their supertype, Cython generates code that looks up the "__init__" attribute of the instance and then calls it through Python using arg tuple/kwargs. This is because the special __init__() method ("tp_init" slot) uses this call signature.

Cython should recognise calls to this method and at least call it directly.

In the (presumably very common) case that the arguments do not use starargs, a more advanced approach would be to split the __init__() method into an internal plain C-function replacement and a tp_init wrapper, and then call the internal function directly, without doing any tuple packing etc. Not sure if it's worth it, though, as the call is already preceded by an (expensive) object allocation.
commented

The same idea is reported in http://trac.cython.org/ticket/141. This should use cpdef semantics.

[robertwb]

scoder commented

The same applies to other special methods like __call__. (noted here to close http://trac.cython.org/ticket/141 as a duplicate)

[robertwb]

scoder commented

The test in tests/run/special_methods_T561.pyx has some test code for this:

6ae0222