[Couenne-tickets] [Couenne, a solver for non-convex MINLP problems] #14: feasible model declared infeasible

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

#14: feasible model declared infeasible
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 Reporter:  stefan      |       Owner:  somebody
     Type:  defect      |      Status:  new     
 Priority:  major       |   Milestone:          
Component:  component1  |     Version:          
 Keywords:              |  
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 Hi,

 with one instance, Couenne 0.4 reports infeasibility, even though SCIP
 reports the instance feasible (objective value 0.0).

 An ampl conversion is
 {{{
 var x2 := 1;
 var x3 >= 0;
 var x4 := 1, >= 0;
 var x5 := 1, <= 2;
 var x6 := 2, <= 2;
 var x7 := 1;
 var x8 >= 0, <= 2;
 var x9 := 1, >= 0, <= 2;
 var x10 := 2, >= 0, <= 2;
 var x11 := 1, >= 0;
 var x12 >= 0;
 var x13 >= 0;
 var x14 := 4, >= 0;
 var x15 := 2, >= 0;
 var x16 >= 0;
 var x17 >= 0;
 var x18 >= 0;
 var x19 >= 0;
 var x20 := 4, >= 0;

 minimize obj: (-1 + x2)^2;

 subject to

 e2:  - x2 + 3*x3 + x4 - x11 = -1;

 e3:  - x2 + x3 + 3*x4 - x12 = 2;

 e4:  - x2 + 3*x5 + x6 + x13 = 4;

 e5:  - x2 + x5 + 3*x6 + x14 = 10;

 e6:  - x2 + x3 + x4 + x5 + x6 + 10*x7 + x8 + x9 + x10 = 16;

 e7:  - x2 + 3*x8 + x9 + x10 - x15 + x16 = 0;

 e8:  - x2 + x8 + 3*x9 + x10 - x17 + x18 = 4;

 e9:  - x2 + x8 + x9 + 3*x10 - x19 + x20 = 10;

 e10: x11*x3 = 0;

 e11: x12*x4 = 0;

 e12: x13*(2 - x5) = 0;

 e13: x14*(2 - x6) = 0;

 e14: x15*x8 = 0;

 e15: x16*(2 - x8) = 0;

 e16: x17*x9 = 0;

 e17: x18*(2 - x9) = 0;

 e18: x19*x10 = 0;

 e19: x20*(2 - x10) = 0;
 }}}

 Can you try to reproduce the problem?

 Couenne output:
 {{{
 NLP0012I
               Num      Status      Obj             It       time
 Location
 NLP0014I             1         OPT 1.640146e-235.5g        4 0.002999g

 Coin0506I Presolve 6 (-28) rows, 3 (-38) columns and 13 (-85) elements
 Clp0006I 0  Obj 0.0001 Primal inf 0.0082958817 (1) Dual inf 1.9999999 (1)
 Clp0006I 0  Obj 0.0001 Primal inf 0.0082958817 (1) Dual inf 1e+10 (2)
 Clp0006I 3  Obj -0.015610312
 Clp0000I Optimal - objective value -0.015610312
 Clp0032I Optimal objective -0.01561031175 - 3 iterations time 0.002,
 Presolve 0.00
 Clp0000I Optimal - objective value -0.015610312
 NLP0014I             2         OPT 1.62459e-215.5g       23 0.014997g
 Clp0000I Optimal - objective value -0.015610312
 Cbc0006I The LP relaxation is infeasible or too expensive
 Cbc0013I At root node, 0 cuts changed objective from -0.015610312 to
 -0.015610312 in 1 passes
 Cbc0014I Cut generator 0 (Couenne convexifier cuts) - 0 row cuts average
 0.0 elements, 2 column cuts (2 active)
 Cbc0001I Search completed - best objective 1e+50, took 0 iterations and 0
 nodes (0.04 seconds)
 Cbc0035I Maximum depth 0, 0 variables fixed on reduced cost
  Couenne convexifier cuts was tried 1 times and created 2 cuts of which 0
 were active after adding rounds of cuts
 }}}

 Couenne 0.3 seems to work, too.

 Stefan

-- 
Ticket URL: <https://projects.coin-or.org/Couenne/ticket/14>
Couenne, a solver for non-convex MINLP problems <https://projects.coin-or.org/Couenne>
Couenne, a solver for non-convex MINLP problems