#11607: read constraints from linear program
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Reporter: john_perry | Owner: ncohen
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-4.7.2
Component: linear programming | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author: john_perry
Merged: | Dependencies:
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Changes (by newvalueoldvalue):
* status: new => needs_review
* author: => john_perry
Old description:
> Sometimes a user might want to read & inspect the constraints in a linear
> program. For example, some code of mine generates a '''lot''' of linear
> programs (I described the project to Nathann once), and it would be nice
> if I could read the constraints off one program so as to combine it with
> another. Example usage would be:
> {{{
> sage: lp = MixedIntegerLinearProgram()
> sage: lp.add_constraint(lp[0]-lp[1],min=1)
> sage: lp.add_constraint(2*lp[1]-lp[0]-lp[2],max=1)
> sage: lp.get_constraints()
> [(1,x_0-x_1),(2*x_1-x_0-x_2,1)]
> }}}
New description:
Sometimes a user might want to read & inspect the constraints in a linear
program. For example, some code of mine generates a '''lot''' of linear
programs (I described the project to Nathann once), and it would be nice
if I could read the constraints off one program so as to combine it with
another. Example usage would be:
{{{
sage: lp = MixedIntegerLinearProgram()
sage: lp.add_constraint(lp[0]-lp[1],min=1)
sage: lp.add_constraint(2*lp[1]-lp[0]-lp[2],max=1)
sage: lp.get_constraints()
[(1.0, ([1, 0],[-1.0, 1.0]), None),(None, ([2, 1, 0], [-1.0, 2.0, -1.0]),
1.0)]
}}}
--
Comment:
I've attached a patch that gives something resembling the desired
functionality, as well as a couple of related, useful methods. I also
changed the description, to mirror the desired result. (I do not really
want to create a new symbolic expression describing a constraint at the
Cython level.)
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11607#comment:1>
Sage <http://www.sagemath.org>
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