error handling bilinear terms in Gurobi 9

Answered

Hossein Haghighat

• December 09, 2019 11:53

hi

When I try to solve a model with bilinear terms in the constraints, in the form X*Y where X is sign-free and Y in bounded, I get the error below: 

Gurobi 9.0.0: NonConvex 2
Gurobi 9.0.0: Gurobi cannot handle quadratic equality constraints.

it should solve this model, but it does not. 

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• 

  Silke Horn

  Gurobi Staff

  • December 09, 2019 12:33

  Hi,

  How are you using Gurobi? This does not look as though the error message is coming directly from Gurobi.

  Are you setting NonConvex=2?

  Silke

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• 

  Hossein Haghighat

  • December 09, 2019 13:11

  

  

  

  I am a user of AMPL and solve models with Gurobi. here is a very simple mode, through I get this error for a sophisticated model as well. 

  constraint C1 must be "<= " otherwise it cannot handle!

  var x ; var y;
  var u >= 0; var v >= 0;
  var r; var s; var t;
  
  minimize obj: u+v ;
  
  s.t. C1: r^2+s^2 = u^2;
  s.t. C2_1: t <= v;
  s.t. C2_2: t >= -v;
  s.t. C3: x+2 = r;
  s.t. C4: y+1 = s;

  s.t. C5: x+y = t; 

   

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• 

  Robert Fourer

  • December 21, 2019 19:58

  

  

  This was cross-posted to the AMPL forum, where the issues were resolved.

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