[Cbc] Incorrect status in solution file for an integer infeasible problem on releases/2.8.10 r2045 and stable/2.8 r2056

[Rémy Roy]

Hello,

I'm using the PuLP library to run Cbc. On my latest installation, I've
decided to try Cbc 2.8.10. Running the PuLP test suite, I've noticed that
the pulpTest060 test failed on both the 2.8.10 release and the current
stable/2.8 version.

The mps file that results from the pulpTest060 test is:

*SENSE:Minimize
NAME          MODEL
ROWS
 N  OBJ
 L  C0000000
 G  C0000001
 E  C0000002
COLUMNS
    X0000000  OBJ        1.00000e+00
    MARK      'MARKER'                 'INTORG'
    X0000001  C0000001   1.00000e+00
    X0000001  C0000000   1.00000e+00
    MARK      'MARKER'                 'INTEND'
    MARK      'MARKER'                 'INTORG'
    X0000002  C0000000   1.00000e+00
    X0000002  C0000002  -1.00000e+00
    MARK      'MARKER'                 'INTEND'
    MARK      'MARKER'                 'INTORG'
    X0000003  C0000001   1.00000e+00
    X0000003  C0000002   1.00000e+00
    MARK      'MARKER'                 'INTEND'
RHS
    RHS       C0000000   5.20000e+00
    RHS       C0000001   1.03000e+01
    RHS       C0000002   7.40000e+00
BOUNDS
 FX BND       X0000000   0.00000e+00
 UP BND       X0000001   4.00000e+00
 LO BND       X0000002  -1.00000e+00
 UP BND       X0000002   1.00000e+00
 UP BND       X0000003   1.00000e+01
ENDATA

The command line executed for running this test is:

cbc /tmp/27068-pulp.mps branch printingOptions rows solution
/tmp/27068-pulp.sol

The stdout for this problem and releases/2.8.10 r2045 is:

Welcome to the CBC MILP Solver
Version: 2.8.10
Build Date: Aug 18 2014
Revision Number: 2056

command line - ./cbc /tmp/27068-pulp.mps branch printingOptions rows
solution /tmp/27068-pulp.sol (default strategy 1)
At line 2 NAME          MODEL
At line 3 ROWS
At line 8 COLUMNS
At line 22 RHS
At line 26 BOUNDS
At line 32 ENDATA
Problem MODEL has 3 rows, 4 columns and 6 elements
Coin0008I MODEL read with 0 errors
Continuous objective value is 0 - 0.00 seconds
Cgl0004I processed model has 1 rows, 2 columns (2 integer) and 2 elements
1 infeasibilities
Problem is infeasible!
Option for printingOptions changed from normal to rows
Total time (CPU seconds):       0.00   (Wallclock seconds):       0.00

The solution file for this problem and releases/2.8.10 r2045 is:

Optimal - objective value 0.00000000
      0 C0000000               5                      0
      1 C0000001            12.4                      0
      2 C0000002             7.4                      0
      0 X0000000               0                      1
      1 X0000001               4                      0
      2 X0000002               1                      0
      3 X0000003             8.4                      0

The stdout and solution file are almost the same for stable/2.8 r2056
except for the version value.

The expected result is that the solution file should start with
"Infeasible" or "Unbounded" instead of "Optimal" for this specific problem.

Regards,

Rémy
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://list.coin-or.org/pipermail/cbc/attachments/20140818/d623027b/attachment.html>