#12309: GLPK crashes or hangs on certain inputs
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Reporter: john_perry | Owner: ncohen
Type: defect | Status: needs_review
Priority: major | Milestone: sage-5.0
Component: linear programming | Keywords:
Work_issues: | Upstream: Reported upstream.
Developers deny it's a bug.
Reviewer: | Author:
Merged: | Dependencies: #10785
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Comment(by ncohen):
> `glp_simplex` doesn't take `iocp` parameters.
Right right, so you need to update its log level too ! Sorry about that.
> Even if true, and it probably is, that would still be overkill
Granted, granted. So I only have two remarks on your patch :
* First, I guess that ``self.scmp`` behaves like ``self.iocp`` and
should also be deallocated in ``__dealloc__``
* Could you add a doctest that shows the signal returned by your code
when a bad lp is solved without the preprocessing flag, and how it is
solved afterwards ? The shortest bad example I was able to produce from
you .py file is this one :
{{{
lp = MixedIntegerLinearProgram(solver="GLPK")
lp.add_constraint( lp[1] +lp[2] -2.0 *lp[3] , max =-1.0)
lp.add_constraint( lp[0] -4.0/3 *lp[1] +1.0/3 *lp[2] , max =-1.0/3) # <--
succeeds up to here w/last line
lp.add_constraint( lp[0] +0.5 *lp[1] -0.5 *lp[2] +0.25 *lp[3] , max
=-0.25) # <--- fails here w/last line
lp.add_constraint( lp[0] +4.0 *lp[1] -lp[2] +lp[3] , max =-1.0) # <-- last
line
lp.solve()
}}}
I also believe the documentation you added about the ``preprocessing``
flag is worth being in a .. WARNING:: environment. This way it'll appear
in red in the HTML documentation, and should attract the attention of
somebody having some troubles with GLPK. That's up to you `:-)`
Sorry if I am being a little slow, there are several nasty patches needing
attention at the same time (not to mention the awful CBC one) and "free
time" is a long-forgotten dream these days `O_o`
Nathann
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12309#comment:7>
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