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4 comments

  • Michel Soares
    Thought Leader

    Hi,

    The presolve step will usually change your model to another equivalent model that is easier for the solver to find a solution. In this step the number of constraints and variables are usually reduced ("Presolve removed 6 rows and 6 columns"), but new variables may also be added. The pre-solved model, in your case, has 18 constraints and 42 integer variables, 36 of them binary.

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  • Muhamad Fikri
    Curious
    Conversationalist

    Hi,

    Thank you for your response.

    So, in my case, this information means that at the initial stage, I have 12 continuous and 36 integers (36 binary). Then, it is reduced to 0 continuous and 42 integers (36 binary). Does it imply the model that I have is an integer without leaving any continuous on it?

    Also, how can I make the continuous variable keep being continuous?

     

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  • Marika Karbstein
    Gurobi Staff Gurobi Staff

    In your example, some of the continuous variables are identified to be implied integers. So, there is an optimal solution where these variables take integer values.

    Also, how can I make the continuous variable keep being continuous?

    What do you mean? What do you want to achieve?

    Maybe the article How does presolve work? helps and gives some more insights.

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  • Muhamad Fikri
    Curious
    Conversationalist

    Hi,

    Thank you for the explanation.

    What I mean is I just want to know, if, in the initial stage, I have 12 continuous and 36 integers (36 binary). Then, the second one the continuous variable still exists. Not zero continuous like in this information (0 continuous and 42 integers (36 binary) ).
    I just want to understand the meaning of it.

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