Martina Gherardi

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Activity overview

Latest activity by Martina Gherardi

  • Martina Gherardi created a post,

    MIP start and Heuristic callback

    Answered
    1. Community
    2. Programming

    Hi, I would like to receive a message about constraint violation when using heuristic callback. When I warm start the model, if there is an infeasibility, I obtain   user MIP start violates constra...

    • Martina Gherardi
    • 2 followers
    • 1 comment
    • 0 votes

  • Martina Gherardi commented,

    1. Community
    2. Programming
    3. Usercuts in the root node with Gurobi Callback

    Hi Marika,  Thanks for the answer.  Actually I'm using Gurobi 11.  It seemed to me that the parameter GRB_CB_MIPNODE_NODCNT  was not effective, so I replaced it with GRB_CB_MIP_NODCNT. With the one...

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    • Martina Gherardi
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  • Martina Gherardi created a post,

    Usercuts in the root node with Gurobi Callback

    Awaiting user input
    1. Community
    2. Programming

    Hi,  I would like to add user cuts in the root node using Julia. With the code cb_calls = Cint[] function my_callback_function(cb_data, cb_where::Cint) push!(cb_calls, cb_where) if cb_where != ...

    • Martina Gherardi
    • 2 followers
    • 3 comments
    • 0 votes

  • Martina Gherardi commented,

    1. Community
    2. Algorithms
    3. Why is Gurobi returning MIP solution with gap of 0 which is not close to the actual optimal solution?

    Hi Jaromił,  thank you for your answer.  I set the bounds to the variables participating in bilinear terms by adding additional constraints to the model. Can you suggest a better way to provide the...

  • Martina Gherardi commented,

    1. Community
    2. Algorithms
    3. Why is Gurobi returning MIP solution with gap of 0 which is not close to the actual optimal solution?

    Hi, I am facing a similar issue with Gurobi 10.0.1. By considering a minimization problem, I observed the following solutions:  1) with MIPGap=1%, in 21 seconds I found a solution with gap=0.9898%...

  • Martina Gherardi created a post,

    Warm start Non-Convex Quadratic Optimization in GAMS

    Answered
    1. Community
    2. Programming

    Hi,  I am trying to warm-start a model with bilinear constraints and continuous variables to the locally optimal solution found with IPOPT.  Accorded to  https://support.gurobi.com/hc/en-us/communi...

    • Martina Gherardi
    • 2 followers
    • 1 comment
    • 0 votes

  • Martina Gherardi commented,

    1. Community
    2. Feature Requests
    3. Nonconvex=2 and Presolve

    Hi Jaromił,  Thank you. Since the model is not reformulated in a mixed integer model, I still do not understand the meaning of the (optimality) gap that I see when I solve my model. Could you help ...

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    • Martina Gherardi
    • 0 votes

  • Martina Gherardi commented,

    1. Community
    2. Feature Requests
    3. Nonconvex=2 and Presolve

    Hi Jaromił,  Thank you for your very clear answer.  If it is possible, I would like to ask you also another question related to the model: the log file shows "Continuous model is non-convex – solvi...

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    • Martina Gherardi
    • 0 votes

  • Martina Gherardi created a post,

    Nonconvex=2 and Presolve

    Answered
    1. Community
    2. Feature Requests

    Hi,  I have a problem that contains 9 bilinear constraints: each constraint has a product of 2 continuous variables. Note that the problem has only continuous variables.  I modeled the problem in G...

    • Martina Gherardi
    • 2 followers
    • 5 comments
    • 0 votes