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Re: [Bug-glpk] Assertion failed: x >= lb; file glpmip2.c; line 230


From: Andrew Makhorin
Subject: Re: [Bug-glpk] Assertion failed: x >= lb; file glpmip2.c; line 230
Date: Tue, 14 Mar 2006 12:57:33 +0300

Thank you very much for the bug report.

The bug appears due to excessive round-off errors on computing values
of variables for some lp relaxation that, in turn, happens because
the problem is badly scaled.

Nevertheless, I successfully solved your instance by glpsol 4.9 with
all options default; --intopt is useless for your problem, because
no reducing is made. (Interesting to note that the solver used much
less b&b nodes than reported in your message.)

Reading model section from bug.mod...
38 lines were read
Generating postive...
Generating negative...
Generating e...
Model has been successfully generated
ipp_basic_tech:  1 row(s) and 0 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
lpx_intopt: presolved MIP has 8192 rows, 65 columns, 24512 non-zeros
lpx_intopt: 64 integer columns, none of which are binary
lpx_adv_basis: size of triangular part = 8192
Solving LP relaxation...
      0:   objval =   0.000000000e+00   infeas =   1.000000000e+00 (0)
    200:   objval =   5.807294690e-01   infeas =   3.110704881e-01 (0)
    400:   objval =   6.197723402e-01   infeas =   2.680607306e-01 (0)
. . .
+  6577: mip =   1.879661681e-04 >=   8.245814104e-05  56.1% (39; 498)
+  6582: mip =   1.879661681e-04 >=   8.245814104e-05  56.1% (44; 498)
+  6587: mip =   1.879661681e-04 >=   8.245814104e-05  56.1% (49; 498)
+  6593: mip =   1.879661681e-04 >=   8.245814104e-05  56.1% (55; 498)
+  6603: mip =   1.879661681e-04 >=   8.245814104e-05  56.1% (57; 500)
+  6614: mip =   1.879661681e-04 >=   8.245814104e-05  56.1% (60; 502)
+  6618: mip =   1.305202946e-04 >=   8.245814104e-05  36.8% (59; 503)
+  6619: mip =   1.302075651e-04 >=   8.245814104e-05  36.7% (54; 515)
+  6625: mip =   1.302075651e-04 >=   8.245814104e-05  36.7% (13; 593)
+  6632: mip =   1.302075651e-04 >=   8.245814104e-05  36.7% (6; 600)
+  6643: mip =   1.302075651e-04 >=     tree is empty   0.0% (0; 633)
INTEGER OPTIMAL SOLUTION FOUND
Time used:   114.0 secs
Memory used: 10.0M (10489004 bytes)
p = [ 4096 4094 4088 4078 4064 4046 4024 3998 3969 3935 3898 3856 3811 3763 3710
 3654 3595 3532 3465 3395 3322 3245 3166 3083 2997 2908 2817 2722 2625 2526 2424
 2320];
q = [-47 -175 -302 -429 -556 -680 -802 -921 -1069 -1179 -1315 -1411 -1531 -1672
-1769 -1884 -2016 -2130 -2224 -2328 -2440 -2526 -2646 -2735 -2821 -2903 -3008 -3
070 -3150 -3246 -3321 -3405 ];
Model has been successfully processed







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