Opened 7 years ago

Closed 7 weeks ago

#123 closed defect (migrated)

CBC.exe produces an "optimal" IP solution that violates a BigM constraint - a scaling problem?

Reported by: amas008 Owned by: tkr
Priority: major Component: Cbc
Version: 2.7.6 Keywords:
Cc: a.mason@…

Description

An OpenSolver? user has sent me a spreadsheet that has some large BigM values. Solving with these large values leads CBC.exe to return a solution reported as optimal that violates at least 1 constraint. Reducing the BigM by a factor of 100 produces a new, now feasible solution.

I have attached (1) Sue's Model - CBC gives wrong answer.txt My summary of the issue (2) model2.lp and modelsolution2.txt Original Input and solution showing the violated constraint (3) model.lp and modelsolution.txt Modified input (smaller BigM) and a new solution that does not violate the modified constraint

Please contact me if you need any more information.

Thanks, Andrew

Attachments (5)

modelsolution2.txt (5.3 KB) - added by amas008 7 years ago.
modelsolution.txt (5.4 KB) - added by amas008 7 years ago.
model2.lp (241.1 KB) - added by amas008 7 years ago.
model.lp (241.1 KB) - added by amas008 7 years ago.
Sue's Model - CBC gives wrong answer.txt (3.8 KB) - added by amas008 7 years ago.

Download all attachments as: .zip

Change History (7)

Changed 7 years ago by amas008

Changed 7 years ago by amas008

Changed 7 years ago by amas008

Changed 7 years ago by amas008

Changed 7 years ago by amas008

comment:1 Changed 7 years ago by tkr

  • Status changed from new to assigned

comment:2 Changed 7 weeks ago by stefan

  • Resolution set to migrated
  • Status changed from assigned to closed

This ticket has been migrated to GitHub and will be resolved there: https://github.com/coin-or/Cbc/issues/123

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