Improve performance by replacing PyTuple_Pack with PyTuple_FromArray

[eendebakpt]

Feature or enhancement

Proposal:

The PyTuple_Pack method is relatively slow because it is a variadic function. For various cases (in particular tuples of size 1 and 2) we can replace PyTuple_Pack with PyTuple_FromArray (introduced in #111489)

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-140009: Improve performance of list_extend_dictitems by using PyTuple_FromArray #140010

[StanFromIreland]

I suggest not applying the easy label if a PR is already open, since these issues are often checked by new contributors, and there not much for them to do here otherwise.

[eendebakpt]

I suggest not applying the easy label if a PR is already open, since these issues are often checked by new contributors, and there not much for them to do here otherwise.

The open PR addresses only one occurrence of PyTuple_Pack, but there potentially more. All the cases for PyTuple_Pack(1, ...) are easy (although not all provide a meaningfull performance improvement), so good to pick up by new contributors.

[kurtmetzger]

If I were to work on this, is it basically changing instances that look like this:
result = PyTuple_Pack(1, basestate);

to this?
PyObject *items[1] = {basestate}; result = PyTuple_FromArray(items, 1);

for all instances where the array would only be 1 or two items?
Thanks

[eendebakpt]

@kurtmetzger Yes, that would be it! But I would wait with pr's for #140132 (comment). If that is accepted, the PyTuple_FromSingle would be even better.

[kurtmetzger]

@eendebakpt I see, so if the other gets accepted, it creates custom functions for arrays of lengths 1 and 2 that should be used like so:
PyTuple_MakePair(a, b)
or
PyTuple_MakeSingle(a)
to replace the current PyTuple_Pack calls?

[eendebakpt]

@eendebakpt I see, so if the other gets accepted, it creates custom functions for arrays of lengths 1 and 2 that should be used like so: PyTuple_MakePair(a, b) or PyTuple_MakeSingle(a) to replace the current PyTuple_Pack calls?

Yes. Note however that #140079 by @sergey-miryanov is there as well, which overlaps.