bpo-24700: Add a fast path for comparing array.array of equal type

[adrian17]

https://bugs.python.org/issue24700

[pitrou]

It confused me that this can be jumped into even when sizes are equal. I would suggest renaming equal_except_size to something else. Perhaps compare_sizes?

[pitrou]

Looks like this change was reversed.

[pitrou]

This lacks a NEWS entry as produced by the blurb utility. Could you add one?

[pitrou]

One thing: how does this fare on arrays of NaNs? Currently we have:

>>> a = array.array("d", [float('nan')])
>>> b = array.array("d", [float('nan')])
>>> a == b
False
>>> a > b
False
>>> a < b
False

[adrian17]

Right, didn't check to handle it. I added a test case for NaN - even if the optimization doesn't get merged, the test case would still be nice to have.

I realized I also missed the PyFPE_START_PROTECT macros. All in all, properly handling floats would either complicate the code a lot, or make the fast path slower in general, so I decided I'd rather just disable the fast path for floats.

[pitrou]

All in all, properly handling floats would either complicate the code a lot, or make the fast path slower in general, so I decided I'd rather just disable the fast path for floats.

Fair enough. Someone else can re-add a fast path for floats if they want to.