[Couenne] Ampl code trying to solve using couenne solver

[Chawal, Ukesh]

Hello,

          I have a weird problem while trying to solve the ampl code using couenne solver. When I tried to minimize it using constraint, X3 = max (0, X1 -2); it gave me the ERROR: unknown operator. But when I used constraint,  X3 = max (0, 9 -2); it gave me the optimal solution. Will you be able to help me with this? I have included the code and the solver output as a reference:-


var X1 >=0 <=9.5 integer;
var X2 >=0 <=9.5 integer;
var X3 >=0 integer;
minimize Y: -2540.33 -154.669 * X1 + 40.0895 * X2 + X3;
subject to a1: X3 = max (0, X1 -2);


ampl: reset;
ampl: include trial.run;
couenne:
ANALYSIS TEST: ERROR: unknown operator (address 0p741f20), aborting.
exit code 18446744073709551615
<BREAK>
*******************************************************************************************************************
var X1 >=0 <=9.5 integer;
var X2 >=0 <=9.5 integer;
var X3 >=0 integer;
minimize Y: -2540.33 -154.669 * X1 + 40.0895 * X2 + X3;
subject to a1: X3 = max (0, 9 -2);


ampl: reset;
ampl: include trial.run;
couenne:
ANALYSIS TEST: Problem size before reformulation: 2 variables (2 integer), 0 constraints.
Problem size after  reformulation: 3 variables (2 integer), 0 constraints.
******************************************************************************
This program contains Ipopt, a library for large-scale nonlinear optimization.
 Ipopt is released as open source code under the Common Public License (CPL).
         For more information visit http://projects.coin-or.org/Ipopt
******************************************************************************
NOTE: You are using Ipopt by default with the MUMPS linear solver.
      Other linear solvers might be more efficient (see Ipopt documentation).
Cbc0012I Integer solution of -3925.35 found by Init Rounding NLP after 0 iterations and 0 nodes (0.00 seconds)
Cbc0001I Search completed - best objective -3925.351, took 0 iterations and 0 nodes (0.00 seconds)
Cbc0035I Maximum depth 0, 0 variables fixed on redu
  "Finished"
couenne: Optimal



Thank You.


Regards,

Ukesh Chawal

Graduate Teaching and Research Assistant

IMSE PhD Student

The University of Texas at Arlington

ukesh.chawal at mavs.uta.edu<https://owa.uta.edu/owa/chawalu@exchange.uta.edu/redir.aspx?SURL=KvdqIrJYYFJEInR__ScoZicftjVuRA8fhtn9F2i-SuhixzhS37PSCG0AYQBpAGwAdABvADoAdQBrAGUAcwBoAC4AYwBoAGEAdwBhAGwAQAB1AHQAYQAuAGUAZAB1AA..&URL=mailto%3aukesh.chawal%40uta.edu>
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