Skip to main content

Lower bound of non-convex problem not improving

Answered

Comments

3 comments

  • Riley Clement
    Gurobi Staff Gurobi Staff

    Hi V,

    Take a look at our section on Most Important Parameters in our documentation.  I would start there, with parameters like MIPFocus and Presolve.

    From your log we can see there is lots of branching, so you may wish to experiment with VarBranch or BranchDir (but note the docs say they rarely help).

    I'd also experiment with our NoRelaxation heuristic.

    Lastly, since you will be comparing the performance under different parameter settings, it may help to make yourself familiar with the following article:  How can I make accurate comparisons?

    - Riley

    0
  • V priya
    Gurobi-versary
    First Comment
    First Question

    Hi, Thank you very much for the references. 

    One more question: When I vary the fixed parameters, some instances with MIPFocus=3 gives 

    Root relaxation: numerical trouble, 0 iterations, 0.00 seconds (0.00 work units)

     

    Is this a scaling problem?

     

     

    0
  • Riley Clement
    Gurobi Staff Gurobi Staff

    MIPFocus is a meta-parameter which is used to influence other parameters.  I expect it is setting making the presolve routine aggressive, which can introduce numerical issues.  Please refer to Solver Parameters to Manage Numerical Issues for ideas but in your case I would try setting Presolve=1, or Aggregate=1, or NumericFocus=1 when using MIPFocus=3 and see if that helps.

    - Riley

    0

Please sign in to leave a comment.