RS01221: CPLEX CAN CLAIM OPTIMALITY ON AN INFEASIBLE NETWORK WITH A SUPPLY/DEMAND IMBALANCE AND NEGATIVE FLOW AT THE ROOT NODE

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You can track all active APARs for this component.

APAR status

  • Closed as fixed if next.

Error description

  • If a network has a supply/demand imbalance that forces flow
    into the root node (i.e. the first node specified in the input),
    CPLEX will declare optimality even though the solution is
    obviously infeasible.  For example, the network
    
    MINIMIZE NETWORK netex1
    SUPPLY
    n1 : 1
    n4 : -5
    ARCS
    a1 : n1 -> n4
    OBJECTIVE
    a1 : 3
    BOUNDS
     0 <= a1 <= 25
    ENDNETWORK
    
    
    Results in
    
    CPLEX> r bad.net
    Problem 'bad.net' read.
    Read time =    0.00 sec.
    CPLEX> net
    Iteration log . . .
    Iteration:     0   Infeasibility     =             5.000000 (5)
    
    Network - Optimal:  Objective =  1.5000000000e+01
    Solution time =    0.00 sec.  Iterations = 1 (1)
    
    This exists for versions 10.0 - 12.5.   It has been fixed
    in 12.5.0.1.
    
    No workaround available.   This will typically only happen
    on tiny networks like the one above where there is no
    flexibility regarding the flows resulting from the imbalance.
    
    Keeping call open for now until additional info regarding the
    network configurations that cause this bug to bite is available.
    

Local fix

  • No workaround available; see problem description for more
    details.
    

Problem summary

  • Some networks with obvious supply/demand imbalances may result
    in an incorrect claim of optimality.
    

Problem conclusion

Temporary fix

  • No.
    

Comments

APAR Information

  • APAR number

    RS01221

  • Reported component name

    ILOG CPLEX

  • Reported component ID

    5724Y4800

  • Reported release

    C50

  • Status

    CLOSED FIN

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2013-01-18

  • Closed date

    2013-01-24

  • Last modified date

    2013-01-24

  • APAR is sysrouted FROM one or more of the following:

  • APAR is sysrouted TO one or more of the following:

Fix information

Applicable component levels

  • RC50 PSY

       UP



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Document information


More support for:

IBM ILOG CPLEX Optimization Studio

Software version:

C50

Reference #:

RS01221

Modified date:

2013-01-24

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