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[Bug-glpk] lpx_get_mip_stat returns LPX_I_UNDEF instead of LPX_I_NOFEAS
From: |
Jean-Sebastien Roy |
Subject: |
[Bug-glpk] lpx_get_mip_stat returns LPX_I_UNDEF instead of LPX_I_NOFEAS |
Date: |
Mon, 15 Mar 2004 23:23:36 +0100 |
User-agent: |
Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.6) Gecko/20040314 |
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
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Jean-Sebastien Roy <=