#15686: Improve documentation of constraint_generation in
MixedIntegerLinearProgramming
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Reporter: equaeghe | Owner:
Type: defect | Status: new
Priority: minor | Milestone: sage-6.1
Component: PLEASE CHANGE | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Changes (by equaeghe):
* priority: major => minor
* type: PLEASE CHANGE => defect
Old description:
> 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.
New description:
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#comment:1>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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