#16244: Simplify TestSuite's some_elements role and logic (no random sampling)
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Reporter: nthiery | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.2
Component: doctest framework | Keywords:
Merged in: | Authors: Nicolas M. Thiéry
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
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Currently `TestSuite` (more precisely `InstanceTester.some_elements`)
tries to be fancy by choosing "some elements" using a random sample. The
random sample is built using Python's `random.sample`, which requires its
input to be a Sequence (the i-th element can be fetched with o[i]), or
some dict-like object. This can get brittle with other kinds of inputs
where `__getitem__` is used for other purposes, or where unranking is just
computationally expensive. The `some_elements` method also assumes
`__len__` to be implemented and cheap enough.
Example:
{{{
FF = IntegerModRing(29)
tester = FF._tester()
list(tester.some_elements(CartesianProduct(FF, FF, FF)))
*bang*
}}}
In fact the following is close to fail, and just works because the error
raised during the sample is caught.
{{{
tester.some_elements(FF)
}}}
This ticket reduces the role of `InstanceTester.some_elements` to just do
some argument parsing and ensure that at most "max_run" elements are
returned. It only requires the input to be iterable.
If we want to have fancy random samples, we should define a specific
protocol (typically P.sample()) for it, or just let parents decide on the
appropriate strategy by defining some_elements appropriately.
This was originaly analyzed in #15919.
--
Ticket URL: <http://trac.sagemath.org/ticket/16244>
Sage <http://www.sagemath.org>
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