[Clp] Objective is nan (sometimes assertion failure)

[John Forrest]

Definitely an error.  Will look into it.

John Forrest

On 06/05/17 23:52, Aleksandr M. Kazachkov wrote:
> The objective is all-zeroes, because I was just checking feasibility 
> at the point the error occurred. When presolve is on, it solves to 
> optimality (objective value 0) and says that it is feasible. When 
> presolve is off, I get nan or an assertion failure.
>
> Now, if I add the first >= constraint as the objective (it is a 
> minimization problem), we should be either primal infeasible or 
> optimal. When presolve is on, I get optimal; when presolve is off, I 
> get "Clp0001I Primal infeasible - objective value -nan".
>
> The lp file with the new objective is attached.
>
> On Sat, May 6, 2017 at 6:32 PM Sébastien Roy 
> <sebastien.roy.sr at gmail.com <mailto:sebastien.roy.sr at gmail.com>> wrote:
>
>     This usually means your linear program is unbounded so the
>     objective function value is infinity. If your modeling a problem
>     that should bound you must have an error in your linear program model.
>
>     On Sat, May 6, 2017 at 6:20 PM, Aleksandr M. Kazachkov
>     <akazachk at cmu.edu <mailto:akazachk at cmu.edu>> wrote:
>
>         Hi everyone,
>
>         I am not sure if there is something wrong with my setup, or if
>         this is a bug, but I would appreciate any help in either case.
>         Thank you in advance!
>
>         I have Clp version 1.16 set up on a Fedora machine. The
>         compilation options are: enable_debug=yes,
>         enable_gnu_packages=yes, and I am using blas and lapack. There
>         are no problems when I run "make test".
>
>         However, on the following LP (which solves fine when using
>         Bcp-1.4.3, which maybe is using an older version of Clp), when
>         presolve (initial) is off, I get that the objective value is
>         "nan". In the context this LP came up (but not when I saved it
>         and ran it on its own), I got the following assertion failure:
>         ../../../Clp/src/ClpSimplexDual.cpp:3216: int
>         ClpSimplexDual::changeBounds(int, CoinIndexedVector*,
>         double&): Assertion `!("should not be here")' failed.
>
>         Specifically, I get the error after the following two lines:
>           solver.setHintParam(OsiDoPresolveInInitial, false);
>           solver.initialSolve();
>
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