Speed up BaseExceptionGroup.{derive,subgroup,split} by ~20%

[sobolevn]

There's a simple change that we can make to increase the preformance of these three methods. Right now they are defined as:

cpython/Objects/exceptions.c

Lines 1491 to 1493 in f4b5588

	{"derive", (PyCFunction)BaseExceptionGroup_derive, METH_VARARGS},
	{"split", (PyCFunction)BaseExceptionGroup_split, METH_VARARGS},
	{"subgroup", (PyCFunction)BaseExceptionGroup_subgroup, METH_VARARGS},

However, they only ever use one argument:

cpython/Objects/exceptions.c

Lines 883 to 885 in f4b5588

	if (!PyArg_ParseTuple(args, "O", &excs)) {
	return NULL;
	}

So, it would be much faster to use METH_O instead. I did these measurements, before and after:

» pyperf timeit -s 'e = BaseExceptionGroup("Message", [ValueError(1)] * 10); i = [TypeError(2)] * 10' 'e.derive(i)'
.....................
Mean +- std dev: 353 ns +- 2 ns

» pyperf timeit -s 'e = BaseExceptionGroup("Message", [ValueError(1)] * 10); i = [TypeError(2)] * 10' 'e.derive(i)'
.....................
Mean +- std dev: 319 ns +- 4 ns

» pyperf timeit -s 'e = BaseExceptionGroup("Message", [ValueError(n) if n % 2 == 0 else TypeError(n) for n in range(100)]); f = lambda e: True' 'e.split(f)'
.....................
Mean +- std dev: 180 ns +- 1 ns

» pyperf timeit -s 'e = BaseExceptionGroup("Message", [ValueError(n) if n % 2 == 0 else TypeError(n) for n in range(100)]); f = lambda e: True' 'e.split(f)'
.....................
Mean +- std dev: 151 ns +- 1 ns

» pyperf timeit -s 'e = BaseExceptionGroup("Message", [ValueError(n) if n % 2 == 0 else TypeError(n) for n in range(100)]); f = lambda e: True' 'e.subgroup(f)'
.....................
Mean +- std dev: 153 ns +- 0 ns

» pyperf timeit -s 'e = BaseExceptionGroup("Message", [ValueError(n) if n % 2 == 0 else TypeError(n) for n in range(100)]); f = lambda e: True' 'e.subgroup(f)'
.....................
Mean +- std dev: 121 ns +- 0 ns

Linked PRs

• gh-111666: Speed up BaseExceptionGroup.{derive,split,subgroup} #111667

[hugovk]

Closing because #111667 was merged, feel free to re-open if needed.