Trying to debug a stack error in GLPK, I am writing the problem out at
every iteration of a column generation scheme
Initially only in the free mps format, but then also in the lp format
One major and one minor error occur:
major: write_freemps does not write the objective function coefficients,
no column has a non-zero in the objective function
minor: write_cpxlp creates one extra variable in the bounds section that
does not appear anywhere else in the problem statement
I have attached two files that are written at the same time in the
algorithm (iteration 2), they illustrate the errors
\* Problem: VRP8 *\
Minimize
obj: + 3111.58854815452 x000001 + 7324.81091523895 x000002
+ 7244.08531869462 x000003 + 4207.01747084559 x000004
+ 5568.0070497061 x000005 + 4795.37657859601 x000006
+ 4063.68189249276 x000007 + 5240.44981827308 x000008
+ 5141.49437088201 x000009 + 6556.49821679987 x000010
+ 7030.34407778006 x000011 + 6657.22271862918 x000012
+ 5650.00054817024 x000013 + 5310.86373581113 x000014
+ 8062.54564230075 x000015 + 4509.25432147977 x000016
+ 5906.40398665519 x000017 + 6631.9274652855 x000018
+ 8339.76066949042 x000019 + 5419.16852525712 x000020
+ 6816.31819043253 x000021 + 7439.14094794803 x000022
+ 1344.80481855175 x000023 + 6891.31725648797 x000024
Subject To
c001: + x000024 + x000022 + x000015 + x000014 + x000012 + x000010
+ x000006 + x000002 = 1
c002: + x000024 + x000022 + x000019 + x000018 + x000012 + x000011
+ x000002 = 1
c003: + x000024 + x000022 + x000021 + x000019 + x000017 + x000015
+ x000013 + x000011 + x000010 + x000005 + x000002 = 1
c004: + x000022 + x000017 + x000016 + x000007 + x000001 = 1
c005: + x000024 + x000020 + x000018 + x000016 + x000014 + x000013
+ x000008 + x000002 = 1
c006: + x000019 + x000018 + x000015 + x000014 + x000012 + x000009
+ x000008 + x000006 + x000004 + x000003 = 1
c007: + x000021 + x000020 + x000017 + x000016 + x000013 + x000011
+ x000010 + x000007 + x000005 + x000003 = 1
c008: + x000023 + x000021 + x000020 + x000009 + x000001 = 1
vc: + x000024 + x000023 + x000022 + x000021 + x000020 + x000019
+ x000018 + x000017 + x000016 + x000015 + x000014 + x000013 + x000012
+ x000011 + x000010 + x000009 + x000008 + x000007 + x000006 + x000005
+ x000004 + x000003 + x000002 + x000001 <= 3
Bounds
x_25 = 0
End
* Problem: VRP8
* Class: LP
* Rows: 10
* Columns: 25
* Non-zeros: 88
* Format: Free MPS
*
NAME VRP8
ROWS
E c001
E c002
E c003
E c004
E c005
E c006
E c007
E c008
L vc
N R0000010
COLUMNS
x000001 vc 1 c008 1
x000001 c004 1
x000002 vc 1 c005 1
x000002 c003 1 c002 1
x000002 c001 1
x000003 vc 1 c007 1
x000003 c006 1
x000004 vc 1 c006 1
x000005 vc 1 c003 1
x000005 c007 1
x000006 vc 1 c001 1
x000006 c006 1
x000007 vc 1 c004 1
x000007 c007 1
x000008 vc 1 c005 1
x000008 c006 1
x000009 vc 1 c008 1
x000009 c006 1
x000010 vc 1 c007 1
x000010 c003 1 c001 1
x000011 vc 1 c002 1
x000011 c003 1 c007 1
x000012 vc 1 c001 1
x000012 c002 1 c006 1
x000013 vc 1 c005 1
x000013 c003 1 c007 1
x000014 vc 1 c006 1
x000014 c001 1 c005 1
x000015 vc 1 c003 1
x000015 c001 1 c006 1
x000016 vc 1 c004 1
x000016 c007 1 c005 1
x000017 vc 1 c004 1
x000017 c007 1 c003 1
x000018 vc 1 c005 1
x000018 c002 1 c006 1
x000019 vc 1 c003 1
x000019 c002 1 c006 1
x000020 vc 1 c008 1
x000020 c007 1 c005 1
x000021 vc 1 c003 1
x000021 c007 1 c008 1
x000022 vc 1 c001 1
x000022 c002 1 c003 1
x000022 c004 1
x000023 vc 1 c008 1
x000024 vc 1 c005 1
x000024 c003 1 c002 1
x000024 c001 1
C0000025 c001 0 $ empty column
RHS
RHS1 c001 1 c002 1
RHS1 c003 1 c004 1
RHS1 c005 1 c006 1
RHS1 c007 1 c008 1
RHS1 vc 3
BOUNDS
FX BND1 C0000025 0
ENDATA
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