[Couenne-tickets] [Couenne, a solver for non-convex MINLP problems] #15: Problems with COUENNE when constraints are swapped

[Couenne, a solver for non-convex MINLP problems]

#15: Problems with COUENNE when constraints are swapped
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 Reporter:  linh        |       Owner:  somebody
     Type:  defect      |      Status:  new     
 Priority:  major       |   Milestone:          
Component:  component1  |     Version:          
 Keywords:              |  
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 I am using AMPL and COUENNE with a very small example

 var x1;
 var x2;

 minimize error: (x1 - 1)^2 ;

 subject to condition1: 0.0002612 + 1.43476/(1 + 100*(x2*0.3)^2 ) - 0.21*x1
 = 0;
 subject to condition2: 0.0001974 + 0.81608/(1 + 100*x1^2 ) - 0.2*x2 = 0;

 The solver can solve and return the results well but when I swap two
 conditions (see below), the solver returns the message "The LP relaxation
 is infeasible or too expensive" and then terminates without returning any
 solution.

 var x1;
 var x2;

 minimize error: (x1 - 1)^2;

 subject to condition2: 0.0001974 + 0.81608/(1 + 100*x1^2) - 0.2*x2 = 0;
 subject to condition1: 0.0002612 + 1.43476/(1 + 100*(x2*0.3)^2) - 0.21*x1
 = 0;

 I write their .nl files and realize that AMPL writes the dual initial
 guess and primal initial guess for the first case into the .nl file

 d2
 0 0
 1 0

 x2
 0 6.833221401328508
 1 0.00186069279294463

 while it does not do that for the second case.

 I also tried these examples with MINOS and they still can solve both
 cases. Could you please help me check it again.

 Thanks,
 Linh

-- 
Ticket URL: <https://projects.coin-or.org/Couenne/ticket/15>
Couenne, a solver for non-convex MINLP problems <https://projects.coin-or.org/Couenne>
Couenne, a solver for non-convex MINLP problems