[Bug-glpk] lpx_get_mip_stat returns LPX_I_UNDEF instead of LPX_I_NOFEAS

[Jean-Sebastien Roy]

Hi !

When trying to solve an infeasible MIP, the lpx_get_mip_stat function 
may answer LPX_I_UNDEF when LPX_I_NOFEAS could be expected.

For example on the attached small MIP (bug.mps), glpsol returns
PROBLEM HAS NO INTEGER FEASIBLE SOLUTION
yet the solution file (bug.sol) contains :
Status:     INTEGER UNDEFINED

Please find the log below.

Regards,

js

$ glpsol bug.mps -o bug.sol
load_mps: reading LP data from `bug.mps'...
load_mps: name `test5'
load_mps: 4 rows
load_mps: 5 columns
load_mps: 20 non-zeros
load_mps: 1 right-hand side vector(s)
load_mps: 0 range vector(s)
load_mps: 1 bound vector(s)
load_mps: 49 cards were read
lpx_simplex: original LP has 4 rows, 5 columns, 20 non-zeros
lpx_simplex: presolved LP has 3 rows, 5 columns, 15 non-zeros
lpx_adv_basis: size of triangular part = 1
      0:   objval =   8.369752929e-01   infeas =   1.000000000e+00 (0)
      3:   objval =   7.534595744e-01   infeas =   0.000000000e+00 (0)
*     3:   objval =   7.534595744e-01   infeas =   0.000000000e+00 (0)
*     4:   objval =   6.046493240e-01   infeas =   0.000000000e+00 (0)
OPTIMAL SOLUTION FOUND
Integer optimization begins...
+     4: mip =     not found yet; lp =   6.046493240e-01 (1, 0)
+     6: mip =     not found yet; lp =     tree is empty (0, 3)
PROBLEM HAS NO INTEGER FEASIBLE SOLUTION
Time used:   0.0 secs
Memory used: 0.2M (158388 bytes)
lpx_print_mip: writing MIP problem solution to `bug.sol'...

*SENSE:Minimize
NAME          test5
ROWS
 N  _C1
 E  _C3
 E  _C2
 E  _C4
COLUMNS
    MARK      'MARKER'                 'INTORG'
    x_4       _C3        8.58741e-01
    x_4       _C2        5.57947e-01
    x_4       _C4        6.98308e-01
    x_4       _C1        7.18745e-01
    MARK      'MARKER'                 'INTEND'
    MARK      'MARKER'                 'INTORG'
    x_0       _C3        9.01301e-01
    x_0       _C2        1.11960e-01
    x_0       _C4        1.22951e-01
    x_0       _C1        4.88581e-01
    MARK      'MARKER'                 'INTEND'
    MARK      'MARKER'                 'INTORG'
    x_1       _C3        7.82617e-01
    x_1       _C2        6.75581e-01
    x_1       _C4        5.22509e-01
    x_1       _C1        1.88665e-01
    MARK      'MARKER'                 'INTEND'
    MARK      'MARKER'                 'INTORG'
    x_2       _C3        8.37716e-01
    x_2       _C2        4.84458e-02
    x_2       _C4        3.99358e-01
    x_2       _C1        5.63730e-01
    MARK      'MARKER'                 'INTEND'
    MARK      'MARKER'                 'INTORG'
    x_3       _C3        1.92867e-01
    x_3       _C2        7.79617e-01
    x_3       _C4        5.57388e-01
    x_3       _C1        1.13761e-01
    MARK      'MARKER'                 'INTEND'
RHS
    RHS       _C3        1.00000e+00
    RHS       _C2        1.00000e+00
    RHS       _C4        1.00000e+00
BOUNDS
 BV BND       x_4     
 BV BND       x_0     
 BV BND       x_1     
 BV BND       x_2     
 BV BND       x_3     
ENDATA

Problem:    test5
Rows:       4
Columns:    5 (5 integer, 5 binary)
Non-zeros:  20
Status:     INTEGER UNDEFINED
Objective:  _C1 = 0 (MINimum) 0.604649324 (LP)

   No.   Row name        Activity     Lower bound   Upper bound
------ ------------    ------------- ------------- -------------
     1 _C1                         0
     2 _C3                         0             1             =
     3 _C2                         0             1             =
     4 _C4                         0             1             =

   No. Column name       Activity     Lower bound   Upper bound
------ ------------    ------------- ------------- -------------
     1 x_4          *              0             0             1
     2 x_0          *              0             0             1
     3 x_1          *              0             0             1
     4 x_2          *              0             0             1
     5 x_3          *              0             0             1

End of output