How to multiply two binary gurobi variables using Java?

Answered

Hadi Askaripoor

February 16, 2022 16:53

• 
• 
• 

Hello, 

I am wondering how I can multiply two gurobi variables in Java! For example, in the following code, I am going to multiply m1, as gurobi binary variable to each gurobi continuous variable in expr10. I would appreciate your guidance!

Best regards,

Hadi

GRBLinExpr expr10 = new GRBLinExpr();
GRBLinExpr expr11 = new GRBLinExpr();
((Process) next).setStart_time(this.model.addVar(0.0, 1000, 0, GRB.CONTINUOUS, "StartingTime"+ ((Process) next).getName()));
GRBVar m1 = model.addVar( 0.0, 1.0, 0.0, GRB.BINARY, "M");
expr10.addTerm(1, listofPairedProcesses.get(0).getStart_time() ); 
expr10.addTerm(-1, listofPairedProcesses.get(1).getStart_time());

0

• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  November 16, 2025 23:43

  This post is more than three years old. Some information may not be up to date. For current information, please check the Gurobi Documentation or Knowledge Base. If you need more help, please create a new post in the community forum, or try Gurobot, our chatbot interface offering instant, expert-level support.
• 

  Maliheh Aramon

  • Gurobi Staff

  February 17, 2022 05:52

  Hi Hadi, 

   

  You can define a Gurobi quadratic expression object (GRBQuadExpr) and iterate through the terms in the GRBLinExpr object already defined and multiply each term by the binary variable \(\texttt{m1}\). Please see the snippet below as an example:

   

  GRBQuadExpr quad_expr = new GRBQuadExpr();
  for (int i=0; i < expr10.size(); ++i) {
    double coeff = expr10.getCoeff(i);
    GRBVar var_1 = expr10.getVar(i);
    quad_expr.addTerm(coeff, var_1, m1);
  }

   

  Best regards,

  Maliheh

  1
• 

  Hadi Askaripoor

  February 21, 2022 12:33

  • 
  • 
  • 

  Dear Maliheh,

  Thanks for your reply! If I want to multiply two gurobi  binary variables e.g. k = m1*m2 and then multiply k to the expr10, how can I proceed? I've tried the same method as you explained but it didn't work!  

  I would appreciate your help!

  0
• 

  Maliheh Aramon

  • Gurobi Staff

  February 23, 2022 05:54 Edited

  Hi Hadi, 

  Sorry for the delay in getting back to you. 

  It should work. I tested the snippet below and it works. Could you please try modifying your code based on the example below and re-run it again?

  GRBVar m1 = model.addVar(0.0, 1.0, 0.0, GRB.BINARY, "m1");
  GRBVar m2 = model.addVar(0.0, 1.0, 0.0, GRB.BINARY, "m2");
  GRBVar k = model.addVar(0.0, 1.0, 0.0, GRB.BINARY, "k");
  // Model k = m1 * m2
  GRBQuadExpr quad_expr_k = new GRBQuadExpr();
  quad_expr_k.addTerm(1, m1, m2);
  model.addQConstr(quad_expr_k, GRB.EQUAL, k, "c1");
  
  // Multiply k by the linear expression
  GRBQuadExpr quad_expr = new GRBQuadExpr();
  for (int i=0; i < expr10.size(); ++i) {
    double coeff = expr10.getCoeff(i);
    GRBVar var_1 = expr10.getVar(i);
    quad_expr.addTerm(coeff, var_1, k);
  }

  Best regards, 

  Maliheh

  0
• 

  Hadi Askaripoor

  February 25, 2022 14:27

  • 
  • 
  • 

  Dear Maliheh,

  It worked, I would really appreciate your help!

  Best regards,

  Hadi

  0

Post is closed for comments.