#13646: Bug in p.add_constraint (when input is True/False)
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Reporter: ncohen | Owner: ncohen
Type: defect | Status: needs_review
Priority: major | Milestone: sage-5.5
Component: linear programming | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Nathann Cohen, Volker Braun | Merged in:
Dependencies: | Stopgaps:
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Changes (by {'newvalue': u'Nathann Cohen, Volker Braun', 'oldvalue': u'Nathann
Cohen'}):
* cc: dimpase (added)
* author: Nathann Cohen => Nathann Cohen, Volker Braun
Old description:
> That awful thing again. See bug report at :
> https://groups.google.com/d/topic/sage-support/VVTWhE0w7i0/discussion
>
> Nathann
New description:
That awful thing again. See bug report at :
https://groups.google.com/d/topic/sage-support/VVTWhE0w7i0/discussion
The problem is that the linear functions need to integrate with the rest
of sage to play nice. The patched mip.pyx adds a parent class for linear
functions and suitable coercion and rich comparison. Now the following
works as expected:
{{{
sage: p = MixedIntegerLinearProgram()
sage: x = p.new_variable()
sage: x[1] >= 10
10 <= x_0
sage: 10 <= x[1]
10 <= x_0
}}}
--
Comment:
I've folded your changes into my patch.
There are two things to do. 1) the chained inequalities need a parent as
well, analogous to linear functions. 2) the base ring of the linear
functions needs to match the capabilities of the backend. I've hardcoded
the base ring as RDF for now. But somebody needs to add a method to the
backends to query their supported base ring so we can plug that into the
linear functions parent.
But I think those can be dealt with separately, and I'll leave them as an
exercise for you :-) The biggest usability wart is patched, at least.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13646#comment:7>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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