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Error 1121 after usercut in generic callback

  • 1.  Error 1121 after usercut in generic callback

    Posted Fri January 27, 2023 10:17 AM

    Hi, I am new here. If this is the wrong place to ask, please tell me.

    I get error "1121: Can't crush solution form" on 8% of about 5000 test instances i am running.

    I am on Cplex using the Python API with python3.10. The error occurs after adding a user cut (via context.add_user_cuts(...)) in a generic callback. Without the cut the instances are fine.

    I tried disabling presolve and other things e.g.
    problem.parameters.preprocessing.presolve = 0
    problem.parameters.preprocessing.dual = -1
    problem.parameters.mip.strategy.presolvenode = 0

    but they dont change anything and turning off presolve does not seem to work at all? because lines like
    MIP Presolve eliminated 50 redundant SOS constraints.
    Tried aggregator 2 times.
    MIP Presolve eliminated 38 rows and 88 columns."

    still show up in the logs.

    I attached the stacktrace of the exception.
    I have no idea how to investigate further and would be very grateful for input.

    Best regards


    Stephan Marnach