#12823: Allow constants for objective function & deletion of rows in
MixedIntegerLinearProgram
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Reporter: john_perry | Owner: ncohen
Type: defect | Status: needs_review
Priority: major | Milestone: sage-5.0
Component: linear programming | Resolution:
Keywords: solver objective | Work issues: failing doctests
Report Upstream: N/A | Reviewers:
Authors: john_perry, ncohen | Merged in:
Dependencies: 12833 | Stopgaps:
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Comment (by ncohen):
Hellooooooo !!!
> That looks perfectly fine. Did you mean `remove_constraints(1)`? That
does look odd, but not very much so.
Yep, that's what I meant. That is precisely how get_values currently works
`^^;`
> Well, in cases where the backend provides a way to add or remove
multiple rows at once (`glpk` for instance), we ought to do that instead,
rather than remove one at a time.
Hmmm, but we can not do that without writing backend-specific code....
> No, that sounds like what ought to be done.
>
> Let me make sure I understand what you're saying: when code that we have
duplicated in `mip.pyx` can be moved to `generic_backend.pyx`, we should
do that. Prime candidates for this are `add_variable(s)`,
`add_linear_constraint(s)`, and `remove_constraint(s)`. We would not
actually remove the functions (yet) though we would deprecate them.
Arggg !! NOononono, I meant duplicated code in the backend files ! That is
where we have 2 functions doing the same stuff, rewritten in 4 different
files ! `:-P`
> If I understand you correctly, here's my counter-proposal: let's finish
this ticket first, then open another that does that, targeted for sage 5.x
where x>0. Otherwise, this gets a little complicated
That is agreed. So do we merge this one ? Oh, the Gurobi/CPLEX thing,
that's right..
Well, that is up to you. I tested them maaaaaaaaany times, but I can also
ask David Coudert to check that tests pass, as he has them installed
(well, CPLEX for sure and I do not know about Gurobi). But you really
should try CPLEX once, it is soooooooooo much faster for integer problems
! `:-)`
Nathann
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12823#comment:24>
Sage <http://www.sagemath.org>
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