#15686: Improve documentation of constraint_generation in
MixedIntegerLinearProgramming
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Reporter: equaeghe | Owner:
Type: PLEASE CHANGE | Status: new
Priority: major | Milestone: sage-6.1
Component: PLEASE CHANGE | Keywords:
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
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As prompted by http://ask.sagemath.org/question/3410, this ticket is meant
for discussion to improve the documentation of the `constraint_generation`
option of MixedIntegerLinearProgramming.
From the ref:
http://www.sagemath.org/doc/reference/numerical/sage/numerical/mip.html:
> constraint_generation – whether to require the returned solver to
support constraint generation (excludes Coin). False by default.
From the source:
https://github.com/sagemath/sage/blob/master/src/sage/numerical/backends/generic_backend.pyx#L983:
> - ``constraint_generation`` (boolean) -- whether the solver returned is
to be used for constraint/variable generation. As the interface with Coin
does not support constraint/variable generation, setting
`constraint_generation` to `False` ensures that the backend to Coin is not
returned when `solver = None`. This is set to `False` by default.
First issue: in the source the phrase “setting `constraint_generation` to
`False` ensures that the backend to Coin is not returned when `solver =
None`” seems incorrect, as setting `constraint_generation` to `False` is
meant to ''allow'' selection of Coin.
Second issue: upon first reading the ref and source documentation, I
understood that Coin would not be selected if `constraint_generation` were
set to `True`, but not what was exactly meant by ‘constraint generation’
in the context of the module. I thought it would enable passing a
constraint generator. Now I understand that constraint generation means:
after a first call `solve()`, one or more constraints is added to the
solved instance, and then `solve()` is called again. Perhaps the
documentation should be changed to make this clearer.
--
Ticket URL: <http://trac.sagemath.org/ticket/15686>
Sage <http://www.sagemath.org>
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