[Dip-tickets] [Dip] #72: Root bound anomaly

[Dip]

#72: Root bound anomaly
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Reporter:  vejlin  |       Type:  defect
  Status:  new     |   Priority:  major 
 Version:  trunk   |   Keywords:        
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 Using the MILPBlock example (with CPLEX 12.1 to solve pricing problems) I
 sometimes get suboptimal root bounds, that is bounds that are worse than
 the simple LP bound.

 Steps to reproduce:
 1) use MILPBlock example
 2) use parameter nodeLimit = 0 (to stop after computing root bound)
 3) use I_16.mps instance file (attached to this ticket)
 4) use I_16.block block file (attached to this ticket)
 5) use BlockFileFormat = List

 On my machine this produces the root bound -183.37 which is worse than the
 simple LP bound of -182.71 (confirmed with CPLEX and with MILBlock using
 an empty block file).

 The bounds seem to always be legal but just suboptimal, so from what I can
 tell this should affect performance but not the correctness of DIP.

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Ticket URL: <https://projects.coin-or.org/Dip/ticket/72>
Dip <https://projects.coin-or.org/Dip>
An extensible software framework for implementing decompositon-based bounding algorithms for use in solving large-scale discrete optimization problems.