#12546: Inequalities in MixedIntegerLinearProgram are not properly handled
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Reporter: ppurka | Owner: ncohen
Type: defect | Status: new
Priority: major | Milestone: sage-5.0
Component: linear programming | Keywords: MixedIntegerLinearProgram
LinearConstraint LinearFunction
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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The `<=` and `>=` inequalities are not properly handled in
`MixedIntegerLinearProgram` - essentially in both
`sage.numerical.mip.LinearConstraint` and
`sage.numerical.mip.LinearFunction`. Here is an example:
{{{
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: b[0] >= b[1] # This is ok
x_1 <= x_0
sage: 1 >= b[1] # This is not since it starts with a constant
False
sage: 1 >= b[1] >= 2*b[0] # Not ok
False
sage: b[2] >= b[1] >= 2*b[0] # Not ok
2 x_0 <= x_1
}}}
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12546>
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