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Infeasibility issue in MIP model built using flopCpp #145

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svigerske opened this issue Mar 3, 2019 · 3 comments

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commented Mar 3, 2019

Issue created by migration from Trac.

Original creator: krakesh.iitk

Original creation time: 2014-02-21 10:46:21

Assignee: @tkralphs

Version: 2.7

CC: krakesh.iitk@gmail.com

Keywords: Infeasibility, Mixed Integer Programming

Hi,

I am solving an assignment and scheduling problem which is MIP and calling OsiCbcSolverInterface from flopCpp to solve it. The solver is throwing that 'The LP relaxation is infeasible and too expensive'. I like to know if there is any functionality in COIN cbc library to check which constraint or group of constraints are causing infeasibility and also how to deal with these infeasibility issues in COIN environment. I know this functinality is available in CPLEX where CPLEX allows users to remove IISs(Irreducible Infeasibility Sets) but could not find it in COIN. May be I am completely unaware that this functionality does exist in COIN but I am unable to locate it. So please help to resolve this.

Thanks,
Rakesh

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commented Mar 3, 2019

Attachment FEMathModel_Phase2.lp by krakesh.iitk created at 2014-02-21 10:48:12

.lp file which contains math model which I am trying to solve

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commented Mar 3, 2019

Attachment FEMathModel_Phase2.mps by krakesh.iitk created at 2014-02-21 10:52:10

this is same model in .mps format as .lp format may not be as stable as .mps

@svigerske svigerske removed the Cbc label Mar 3, 2019

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commented Mar 12, 2019

I'm not aware of any infeasibility-analysis techniques in Cbc. You might want to try reformulating your model to minimize violation of constraints and see whether that gives you some hint.

@svigerske svigerske closed this Mar 12, 2019

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