gh-1076: Use array comparison functions from array-api-extra

[paddyroddy]

Description

As can be seen in scipy/scipy#25143 and scikit-learn/scikit-learn#34019, array-api-extra now provides array comparison methods. This means we should be able to remove our custom Compare helper class.

Closes: #1076

Checks

• Is your code passing linting?
• Is your code passing tests?
• Have you added additional tests (if required)?
• Have you modified/extended the documentation (if required)?
• Have you added a one-liner changelog entry above (if required)?

[prady0t]

Here and everywhere else, we can call xp_assert... inside the class itself, so compare.assert_allclose works but internally calls xp_assert_close. This would help avoid changing lines everywhere.

[paddyroddy]

Yes but the Compare class was always a hack so I'd rather to the big changes once

[prady0t]

Here and everywhere else, instead of changing it everywhere, you can modify the compare class functions first to convert a Python scalar or list into an array, then call the array api extra function with these inputs. See here for example (done in this SciPy PR):

def _convert_scalar_to_array(x, xp):
    if isinstance(x, (list, tuple)) or type(x) in (
        int,
        float,
        complex,
        bool,
    ):
        return xp.asarray(x)
    return x

def xp_assert_close(actual, desired, *, rtol=None, atol=0, check_dtype=True,
                    check_shape=True, check_0d=False, err_msg='', xp=None):

[paddyroddy]

I feel if we did this then we could have just stuck with our initial implementation

[lucascolley]

the advantage of converting array-likes to arrays is that you gain the strictness of checking that the return namespace is what you expect

[lucascolley]

the check_shape=False parameter should be an alternative here

[lucascolley]

the advantage of converting array-likes to arrays is that you gain the strictness of checking that the return namespace is what you expect

[lucascolley]

public API is now available on array-api-extra main and documented at https://data-apis.org/array-api-extra/api-testing.html