#12091: chained inequalities bug in add_constraint to MixedIntegerLinearProgram
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Reporter: dimpase | Owner: ncohen
Type: defect | Status: positive_review
Priority: major | Milestone: sage-5.5
Component: linear programming | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: 13650 | Stopgaps:
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Changes (by dimpase):
* status: needs_review => positive_review
* dependencies: => 13650
Old description:
> This ticket was originally started to address problems now dealt with in
> #13646.
> Still, the following (chained inequalities don't work) needs to be fixed:
> {{{
> sage: p = MixedIntegerLinearProgram()
> sage: b = p.new_variable()
> sage: b[0] <= b[1] <= 2 # This is not ok
> x_1 <= 2
> sage: (b[0] <= b[1] <= 2).constraints # Not ok
> [x_1, 2]
> sage: 1 >= b[1] >= 2*b[0] # Not ok (note that without #13646 this returns
> False)
> 2 x_0 <= x_1
> sage: b[2] >= b[1] >= 2*b[0] # Not ok
> 2 x_0 <= x_1
> }}}
> See also this
> [http://permalink.gmane.org/gmane.comp.mathematics.sage.support/29948
> sage-support thread].
New description:
This ticket was originally started to address problems now dealt with in
#13646.
Still, the following (chained inequalities don't work) needs to be fixed:
{{{
sage: p = MixedIntegerLinearProgram()
sage: b = p.new_variable()
sage: b[0] <= b[1] <= 2 # This is not ok
x_1 <= 2
sage: (b[0] <= b[1] <= 2).constraints # Not ok
[x_1, 2]
sage: 1 >= b[1] >= 2*b[0] # Not ok (note that without #13646 this returns
False)
2 x_0 <= x_1
sage: b[2] >= b[1] >= 2*b[0] # Not ok
2 x_0 <= x_1
}}}
See also this
[http://permalink.gmane.org/gmane.comp.mathematics.sage.support/29948
sage-support thread].
Apply
* [attachment:trac_12091_constraints_parents.patch]
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Comment:
As far as I am concerned, better parsing of things like {{{x[0] <= x[1] >=
x[2]}}} or {{{x[0] <= x[1] == 2}}} can wait till another ticket.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12091#comment:36>
Sage <http://www.sagemath.org>
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