[Couenne] Question about "display" the results

[Pietro Belotti]

Dear Nathalie,

this is most probably an issue with the interface between Cbc (the 
branch-and-bound solver used by Couenne) and the Couenne wrapper for 
Cplex. The former might not be able to access the right data and end up 
with the wrong (-326) value.

You may want to post the model you have used, so that one can replicate 
the problem. Also, if total_income is the name of the objective function 
as specified in the AMPL model, I assume it is associated with an 
expression. What happens when you display that expression instead of 
total_income?

Thanks,
Pietro

--
Pietro Belotti
Dept. of Mathematical Sciences
Clemson University
email: pbelott at clemson.edu
phone: 864-656-6765
web:   myweb.clemson.edu/~pbelott

On Thu, 23 Dec 2010, njamett at uantof.cl wrote:

>
>       Hi
>
>       I'm working with couenne and cplex as a subsolver. I found an optimal, but when I try to display the results, it shows a different solution.
>
>       CPX0000  CPLEX Error  1217: No solution exists.
>       CPX0000  CPLEX Error  1217: No solution exists.
>       CPX0000  CPLEX Error  1217: No solution exists.
>       CPX0000  CPLEX Error  1217: No solution exists.
>       Cbc0001I Search completed - best objective -12707779302.36208, took 557444 iterations and 10274 nodes (275.85 seconds)
>       Cbc0032I Strong branching done 0 times (285622 iterations), fathomed 13 nodes and fixed 185 variables
>       Cbc0035I Maximum depth 282, 4 variables fixed on reduced cost
>       CPX0000  CPLEX Error  1217: No solution exists.
>       CPX0000  CPLEX Error  1217: No solution exists.
>       CPX0000  CPLEX Error  1217: No solution exists.
>       CPX0000  CPLEX Error  1217: No solution exists.
>       CPX0000
>       CPX0000  Iteration           Objective            In Variable           Out Variable
>       CPX0000       1 sI         4645.972072                    x78                    x77
>       CPX0000       2 sI         4645.970457                    x63                    x62
>        Couenne convexifier cuts was tried 34282 times and created 845177 cuts of which 30323 were active after adding rounds of cuts
>
>            "Finished"
>
>       couenne: Optimal
>
>       ampl: display total_income,w,vr,vs,vc,or,os,oc,nr,ns,nc,s1,s2,aj,ak;
>       total_income = -362.768 (best objective)
>
>       w [*,*]
>       :        1          2       :=
>       1    1250        2500
>       2    1250        2500
>       3       0           0
>       4     226.445    1755.75
>       5       0           0
>       6       0           0
>       7       0           0
>       8       0           0
>       9       0           0
>       10    226.445    1755.75
>       11     57.2661   1590.52
>       12      0           0
>       13      0           0
>       14      0           0
>
>       I solved the same problem using Couenne without Cplex and I got almost the same result ( total income-12E-10). I when i did the display i didn't have any problem. Do
>       you know why I have troubles in display when I use Couenne with Cplex?
>
>       Thank you
>
>       Best regards.
>
>       Nathalie Jamett
>       PhD Student
>       University of Antofagasta
>       Chile.
> 
> 
> 
>