Hi, when running GLPK 4.20 on the attached LP without presolver and letting it start from the standard basis (not advanced), I get a wrong final basis.
The LP contains a row
sum_{i=1..20} x_i = 1
where the variables x_i do not appear somewhere else in the LP.
(x_i correspond to C00000i in the mps file)
I would expect to have at least one of the x_i in the basis, and that is
also the case when the presolver is used or GLPK starts from the
advanced basis (x_20 gets into the basis). However, when running
glpsol --nopresol --std --mps lp03.mps -o lp03.sol
all variables are reported as NF (see attached solution file).
Best,
Stefan
lp03.mps
Description: application/mps
Problem: <none_lo
Rows: 7
Columns: 26
Non-zeros: 38
Status: OPTIMAL
Objective: R0000000 = 178.425 (MINimum)
No. Row name St Activity Lower bound Upper bound Marginal
------ ------------ -- ------------- ------------- ------------- -------------
1 R0000000 B 178.425
2 R0000001 NU 350 350 -0.09
3 R0000002 B 550 600
4 R0000003 NL 325 325 0.315
5 R0000004 NL 300 300 0.243
6 R0000005 NL 275 275 0.126
7 R0000006 B 0 0 =
No. Column name St Activity Lower bound Upper bound Marginal
------ ------------ -- ------------- ------------- ------------- -------------
1 C0000001 NF 0 < eps
2 C0000002 NF 0 < eps
3 C0000003 NF 0 < eps
4 C0000004 NF 0 < eps
5 C0000005 NF 0 < eps
6 C0000006 NF 0 < eps
7 C0000007 NF 0 < eps
8 C0000008 NF 0 < eps
9 C0000009 NF 0 < eps
10 C0000010 NF 0 < eps
11 C0000011 NF 0 < eps
12 C0000012 NF 0 < eps
13 C0000013 NF 0 < eps
14 C0000014 NF 0 < eps
15 C0000015 NF 0 < eps
16 C0000016 NF 0 < eps
17 C0000017 NF 0 < eps
18 C0000018 NF 0 < eps
19 C0000019 NF 0 < eps
20 C0000020 NF 0 < eps
21 C0000021 B 50 0
22 C0000022 B 300 0
23 C0000023 NL 0 0 0.126
24 C0000024 B 275 0
25 C0000025 NL 0 0 0.009
26 C0000026 B 275 0
Karush-Kuhn-Tucker optimality conditions:
KKT.PE: max.abs.err. = 1.28e-13 on row 1
max.rel.err. = 2.25e-16 on row 1
High quality
KKT.PB: max.abs.err. = 0.00e+00 on row 0
max.rel.err. = 0.00e+00 on row 0
High quality
KKT.DE: max.abs.err. = 0.00e+00 on column 0
max.rel.err. = 0.00e+00 on column 0
High quality
KKT.DB: max.abs.err. = 0.00e+00 on row 0
max.rel.err. = 0.00e+00 on row 0
High quality
End of output
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