#11606: simplify constraints in linear programs
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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
Comment:
The attached file is a first attempt at solving the problem. An optional
argument, `check_redundant`, which defaults to `False`, is used to control
whether to invoke the change. If so:
* it proceeds row by row of the constraint matrix
* it checks whether the same variables are nonzero
* if so, it computes the ratio `r` between the coefficients of the
"leading" variables
* if it is negative, add the constraint
(if `r` is negative, the constraint is not so obviously redundant)
* if the ratio of the lower & upper bounds disagrees with `r`, add the
constraint
* now check the ratio of the remaining variables in the current row; if
it differs from `r`, add the constraint
This is meant to be a preliminary implementation rather than an efficient
implementation; the best option is probably to visit the matrix & compare,
but this would require going into each back end, which is probably a bad
idea right now.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11606#comment:2>
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