RS01173: CPXGETMIPRELGAP CAN RETURN INCORRECT, ESSENTIALLY INFINITE VALUE WHEN BEFORE LP HEURISTICS PROVE OPTIMALITY AT THE ROOT NODE.

Subscribe

You can track all active APARs for this component.

APAR status

  • Closed as program error.

Error description

  • This can only  happen on trivial problems that can
    be solved via simple heuristics before starting
    branch and bound.   In that case, CPXgetmiprelgap
    doesn't update the relative gap properly and returns
    a large value (essentially because the list of active
    nodes in the tree is empty, so the best node is infinite).
    
    Registered as RTC-14697.
    
    Workaround: check for status of optimal, in which case the
    relative and absolute gaps are always 0.
    

Local fix

  • Workaround: check for status of optimal, in which case the
    relative and absolute gaps are always 0.
    

Problem summary

  • Incorrect relative gap on MIP models where pre root node
    heuristics solve to optimality.
    

Problem conclusion

  • Fixed in 12.5.0.1; easy workarounds available.
    

Temporary fix

  • Gap is always 0 when status is optimal; can use that as
    workaround.
    

Comments

APAR Information

  • APAR number

    RS01173

  • Reported component name

    ILOG CPLEX

  • Reported component ID

    5724Y4800

  • Reported release

    C50

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2012-12-06

  • Closed date

    2012-12-20

  • Last modified date

    2012-12-20

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

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

Fix information

  • Fixed component name

    ILOG CPLEX

  • Fixed component ID

    5724Y4800

Applicable component levels

  • RC50 PSY

       UP



Rate this page:

(0 users)Average rating

Document information


More support for:

IBM ILOG CPLEX Optimization Studio

Software version:

C50

Reference #:

RS01173

Modified date:

2012-12-20

Translate my page

Machine Translation

Content navigation