[Bug-glpk] Variables erroneously read as binary?

[Roberto Bagnara]

After an upgrade to Fedora 12 (which ships GLPK 4.40) the attached
MPS is interpreted as having all binary variables:

$ glpsol --min ~/ppl/ppl/demos/ppl_lpsol/examples/ex1.mps
GLPSOL: GLPK LP/MIP Solver 4.40
Parameter(s) specified in the command line:
  --min /home/roberto/ppl/ppl/demos/ppl_lpsol/examples/ex1.mps
Reading problem data from 
`/home/roberto/ppl/ppl/demos/ppl_lpsol/examples/ex1.mps'...
Problem: from_lp_file
Objective: r_000000
3 rows, 2 columns, 6 non-zeros
2 integer variables, all of which are binary
19 records were read
ipp_basic_tech:  3 row(s) and 2 column(s) removed
ipp_reduce_bnds: 1 pass(es) made, 0 bound(s) reduced
ipp_basic_tech:  0 row(s) and 0 column(s) removed
ipp_reduce_coef: 1 pass(es) made, 0 coefficient(s) reduced
Objective value = -2
INTEGER OPTIMAL SOLUTION FOUND BY MIP PRESOLVER
Time used:   0.0 secs
Memory used: 0.0 Mb (45508 bytes)

On Fedora 10 (which ships GLPK 4.36) the same file is interpreted
as having no binary variables:

$ glpsol --min ~/ppl/ppl/demos/ppl_lpsol/examples/ex1.mps
glp_read_mps: reading problem data from 
`/home/bagnara/ppl/ppl/demos/ppl_lpsol/examples/ex1.mps'...
glp_read_mps: problem from_lp_file
glp_read_mps: 3 rows, 2 columns, 6 non-zeros
glp_read_mps: 2 integer columns, none of which are binary
glp_read_mps: 19 records were read
ipp_basic_tech:  1 row(s) and 0 column(s) removed
ipp_reduce_bnds: 2 pass(es) made, 2 bound(s) reduced
ipp_basic_tech:  0 row(s) and 0 column(s) removed
ipp_reduce_coef: 1 pass(es) made, 0 coefficient(s) reduced
glp_intopt: presolved MIP has 2 rows, 2 columns, 4 non-zeros
glp_intopt: 2 integer columns, none of which are binary
Scaling...
  A: min|aij| =  1.000e+00  max|aij| =  4.000e+00  ratio =  4.000e+00
Problem data seem to be well scaled
Crashing...
Size of triangular part = 2
Solving LP relaxation...
*     0: obj =   0.000000000e+00  infeas =  0.000e+00 (0)
*     2: obj =  -3.750000000e+00  infeas =  0.000e+00 (0)
OPTIMAL SOLUTION FOUND
Integer optimization begins...
+     2: mip =     not found yet >=              -inf        (1; 0)
+     4: >>>>>  -3.000000000e+00 >=  -3.000000000e+00   0.0% (2; 0)
+     4: mip =  -3.000000000e+00 >=     tree is empty   0.0% (0; 3)
INTEGER OPTIMAL SOLUTION FOUND
Time used:   0.0 secs
Memory used: 0.1 Mb (84145 bytes)
address@hidden ppl_lpsol]$ rpm -q glpsol
package glpsol is not installed
address@hidden ppl_lpsol]$ qpm -k glpk-utils
-bash: qpm: command not found
address@hidden ppl_lpsol]$ rpm -q glpk-utils
glpk-utils-4.36-1.fc10.x86_64
address@hidden ppl_lpsol]$
address@hidden ppl_lpsol]$ glpsol --min 
~/ppl/ppl/demos/ppl_lpsol/examples/ex1.mps
glp_read_mps: reading problem data from 
`/home/bagnara/ppl/ppl/demos/ppl_lpsol/examples/ex1.mps'...
glp_read_mps: problem from_lp_file
glp_read_mps: 3 rows, 2 columns, 6 non-zeros
glp_read_mps: 2 integer columns, none of which are binary
glp_read_mps: 19 records were read
ipp_basic_tech:  1 row(s) and 0 column(s) removed
ipp_reduce_bnds: 2 pass(es) made, 2 bound(s) reduced
ipp_basic_tech:  0 row(s) and 0 column(s) removed
ipp_reduce_coef: 1 pass(es) made, 0 coefficient(s) reduced
glp_intopt: presolved MIP has 2 rows, 2 columns, 4 non-zeros
glp_intopt: 2 integer columns, none of which are binary
Scaling...
  A: min|aij| =  1.000e+00  max|aij| =  4.000e+00  ratio =  4.000e+00
Problem data seem to be well scaled
Crashing...
Size of triangular part = 2
Solving LP relaxation...
*     0: obj =   0.000000000e+00  infeas =  0.000e+00 (0)
*     2: obj =  -3.750000000e+00  infeas =  0.000e+00 (0)
OPTIMAL SOLUTION FOUND
Integer optimization begins...
+     2: mip =     not found yet >=              -inf        (1; 0)
+     4: >>>>>  -3.000000000e+00 >=  -3.000000000e+00   0.0% (2; 0)
+     4: mip =  -3.000000000e+00 >=     tree is empty   0.0% (0; 3)
INTEGER OPTIMAL SOLUTION FOUND
Time used:   0.0 secs
Memory used: 0.1 Mb (84145 bytes)

All the best,

    Roberto

-- 
Prof. Roberto Bagnara
Applied Formal Methods Laboratory
Department of Mathematics, University of Parma, Italy
http://www.cs.unipr.it/~bagnara/
mailto:address@hidden

ex1.mps
Description: Text document