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[Bug-glpk] Numerical instability


From: Hanzalek Zdenek
Subject: [Bug-glpk] Numerical instability
Date: Tue, 15 Apr 2008 13:53:34 +0400

Dear maintainers of wonderfull glpk solver,

tho following error occured wile version 4.26 on attached ILP problem.

Any advice how to avoid such problems is welcome.

With kind regards 

Zdenek
----------
Reading model section from ilpp_adctlvxxxx.mod...
137 lines were read
Reading data section from ilpp_adctlvxxxx.dat...
104 lines were read
Generating obj...
Generating calculate_crit...
Generating leave_once...
Generating fit_capacity...
Generating leave_depot...
Generating enter_leave...
Generating enter_depot...
Generating arrival_travel_arrival...
Generating before_latest...
Generating after_earliest...
Generating floating_shift...
Generating zero_enter_first...
Generating zero_leave_last...
Generating zero_diagonal...
Model has been successfully generated
lpx_write_cpxlp: writing problem data to `ilpp_adctlvxxxx.lp'...
glp_simplex: original LP has 937 rows, 561 columns, 3212 non-zeros
glp_simplex: presolved LP has 386 rows, 380 columns, 2080 non-zeros
lpx_adv_basis: size of triangular part = 376
      0:   objval =  0.000000000e+000   infeas =  1.000000000e+000 (10)
     15:   objval =  2.868686869e+000   infeas =  7.587469242e-017 (10)
*    15:   objval =  2.868686869e+000   infeas =  2.775557562e-016 (10)
*    16:   objval =  1.039612840e-012   infeas =  2.220446049e-016 (10)
OPTIMAL SOLUTION FOUND
Integer optimization begins...
+    16: mip =     not found yet >=              -inf        (1; 0)
+   123: >>>>>  1.776200000e+004 >=  0.000000000e+000 100.0% (5; 0)
+   575: >>>>>  1.738300000e+004 >=  0.000000000e+000 100.0% (14; 7)
+  8998: mip =  1.738300000e+004 >=  0.000000000e+000 100.0% (81; 339)
+ 17836: mip =  1.738300000e+004 >=  0.000000000e+000 100.0% (167; 648)
+ 26841: mip =  1.738300000e+004 >=  0.000000000e+000 100.0% (258; 947)
+ 35668: mip =  1.738300000e+004 >=  0.000000000e+000 100.0% (343; 1269)
spx_simplex: warning: numerical instability (dual simplex)
+ 44471: mip =  1.738300000e+004 >=  0.000000000e+000 100.0% (422; 1596)
+ 54167: mip =  1.738300000e+004 >=  0.000000000e+000 100.0% (484; 1903)
GLPK internal error: x <= ub; file ..\src\glpios03.c, line 265 

--
Zdenek Hanzalek
Department of Control Engineering, Faculty of Electrical Engineering
Czech Technical University in Prague, Karlovo namesti 13, 121 35 Prague 2,
Czech Republic
tel: +420 224355708  address@hidden
fax: +420 224355703  http://dce.felk.cvut.cz/hanzalek/

Attachment: ilpp_adctlvxxxx.mod
Description: Binary data

Attachment: ilpp_adctlvxxxx.dat
Description: Binary data


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