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[Bug-glpk] Difference, 32bit build - 64bit build


From: Christoph Cullmann
Subject: [Bug-glpk] Difference, 32bit build - 64bit build
Date: Wed, 24 Sep 2008 20:15:19 +0200
User-agent: KMail/1.10.1 (Linux/2.6.27-2-generic; KDE/4.1.1; x86_64; ; )

Hi,

I have a difference with solving a larger problem on 32bit and 64bit linux,
libglpk 4.31 build from tarball, no patches, gcc-4.1, no fancy optimizations, 
-O0.

On 32bit, I get:

address@hidden:/local/cullmann/build/libglpk.default/usr/bin$ ./glpsol --cpxlp 
~/value_15318949093.lp
glp_read_lp: reading problem data from `/home/cullmann/value_15318949093.lp'...
glp_read_lp: 1015 rows, 1577 columns, 3513 non-zeros
glp_read_lp: 1577 integer columns, none of which are binary
glp_read_lp: 2949 lines were read
glp_simplex: original LP has 1015 rows, 1577 columns, 3513 non-zeros
glp_simplex: presolved LP has 712 rows, 874 columns, 1942 non-zeros
Scaling...
 A: min|aij| =  1.000e+00  max|aij| =  6.000e+00  ratio =  6.000e+00
Problem data seem to be well scaled
Crashing...
Size of triangular part = 666
      0: obj =   1.877000000e+03  infeas =  2.400e+01 (46)
*     3: obj =   1.877000000e+03  infeas =  0.000e+00 (46)
*   200: obj =   1.383603996e+10  infeas =  0.000e+00 (0)
*   400: obj =   1.495135855e+10  infeas =  0.000e+00 (0)
*   558: obj =   1.531894909e+10  infeas =  0.000e+00 (0)
OPTIMAL SOLUTION FOUND
Integer optimization begins...
+   558: mip =     not found yet <=              +inf        (1; 0)
+   558: mip =     not found yet <=     tree is empty        (0; 1)
PROBLEM HAS NO INTEGER FEASIBLE SOLUTION

While on 64bit, the same problem yields a solution:

address@hidden:/local/cullmann/build/glpsolve.default/usr/bin$ ./glpsol --cpxlp 
~/value_15318949093.lp
glp_read_lp: reading problem data from `/home/cullmann/value_15318949093.lp'...
glp_read_lp: 1015 rows, 1577 columns, 3513 non-zeros
glp_read_lp: 1577 integer columns, none of which are binary
glp_read_lp: 2949 lines were read
glp_simplex: original LP has 1015 rows, 1577 columns, 3513 non-zeros
glp_simplex: presolved LP has 712 rows, 874 columns, 1942 non-zeros
Scaling...
 A: min|aij| =  1.000e+00  max|aij| =  6.000e+00  ratio =  6.000e+00
Problem data seem to be well scaled
Crashing...
Size of triangular part = 666
      0: obj =   1.877000000e+03  infeas =  2.400e+01 (46)
*     3: obj =   1.877000000e+03  infeas =  0.000e+00 (46)
*   200: obj =   1.383603996e+10  infeas =  0.000e+00 (0)
*   400: obj =   1.495135855e+10  infeas =  0.000e+00 (0)
*   559: obj =   1.531894909e+10  infeas =  0.000e+00 (0)
OPTIMAL SOLUTION FOUND
Integer optimization begins...
+   559: mip =     not found yet <=              +inf        (1; 0)
+   559: >>>>>   1.531894909e+10 <=   1.531894909e+10   0.0% (1; 0)
+   559: mip =   1.531894909e+10 <=     tree is empty   0.0% (0; 1)
INTEGER OPTIMAL SOLUTION FOUND
Time used:   0.1 secs
Memory used: 1.3 Mb (1400268 bytes)

I have verified the 64bit solution using CPLEX, which yields the same value.

Any ideas, what this might cause?
Interesting sidenote: the debian shipped glpsol, version 4.16 works on both 
32bit
and 64bit linux systems with same sane result.

The input LP is attached, CPLEX format. Any advice welcome :)

cu
Christoph

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-------------------------------------- Christoph Cullmann ---------
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Attachment: value_15318949093.lp
Description: Text document


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