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[Help-glpk] different executions on different platforms
From: |
François Galea |
Subject: |
[Help-glpk] different executions on different platforms |
Date: |
Thu, 14 Feb 2008 13:58:04 +0100 |
User-agent: |
Mozilla-Thunderbird 2.0.0.9 (X11/20080110) |
hi,
We have noticed that executing the glpsol command-line solver on
different machines with the same input data could lead to different
execution. The number of simplex iterations / branch-and-bound nodes may
differ, which leads to different performance.
We have done our testings on three different platforms :
- cygwin on top of Windows XP (i386 processor)
- Debian GNU/Linux (i386)
- Debian GNU/Linux (amd64)
All testings were done using GLPK 4.25.
The three attached execution logs correspong the resolution of the
pp08a.mps instance from MIPLIB 2003, using the --cuts option of glpsol.
In summary :
- on cygwin : 66 simplex iterations at root, 10059 total, 981 b&b nodes.
- i386 Linux : the values are 66, 16377, 1449.
- amd64 Linux : 67, 13155, 1445.
The execution times cannot be compared, as the executions were performed
on different machines.
Does anybody have an explanation why there are such differencies ? I
have started looking into the internal random number generator, but it
seems to behave the same way on the different platforms.
Best regards,
François
lpx_read_freemps: reading problem data from `./Problemes/pp08a.mps'...
lpx_read_freemps: problem pp08a
lpx_read_freemps: 137 rows, 240 columns, 656 non-zeros
lpx_read_freemps: 64 integer columns, all of which are binary
lpx_read_freemps: 657 records were read
ipp_basic_tech: 1 row(s) and 0 column(s) removed
ipp_reduce_bnds: 2 pass(es) made, 64 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 136 rows, 240 columns, 480 non-zeros
lpx_intopt: 64 integer columns, all of which are binary
lpx_adv_basis: size of triangular part = 128
Solving LP relaxation...
0: objval = 8.580000000e+03 infeas = 1.000000000e+00 (0)
60: objval = 2.750607143e+03 infeas = 0.000000000e+00 (1)
* 60: objval = 2.750607143e+03 infeas = 0.000000000e+00 (1)
* 66: objval = 2.748345238e+03 infeas = 0.000000000e+00 (0)
OPTIMAL SOLUTION FOUND
Creating the conflict graph...
The conflict graph is either empty or too big
Generating cutting planes...
& 66: obj = 2.748345238e+03 frac = 53 cuts = 0 (0)
& 66: obj = 2.748345238e+03 frac = 53 cuts = 0 (0)
Integer optimization begins...
+ 66: mip = not found yet >= -inf (1; 0)
Gomory's cuts enabled
MIR cuts enabled
+ 969: >>>>> 7.580000000e+03 >= 7.139485665e+03 5.8% (47; 0)
+ 1882: >>>>> 7.510000000e+03 >= 7.171523233e+03 4.5% (136; 3)
+ 3815: >>>>> 7.350000000e+03 >= 7.213155655e+03 1.9% (272; 58)
+ 10059: mip = 7.350000000e+03 >= tree is empty 0.0% (0; 981)
INTEGER OPTIMAL SOLUTION FOUND
Time used: 6.0 secs
Memory used: 1.5 Mb (1602726 bytes)
lpx_read_freemps: reading problem data from `../Problemes/pp08a.mps'...
lpx_read_freemps: problem pp08a
lpx_read_freemps: 137 rows, 240 columns, 656 non-zeros
lpx_read_freemps: 64 integer columns, all of which are binary
lpx_read_freemps: 657 records were read
ipp_basic_tech: 1 row(s) and 0 column(s) removed
ipp_reduce_bnds: 2 pass(es) made, 64 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 136 rows, 240 columns, 480 non-zeros
lpx_intopt: 64 integer columns, all of which are binary
lpx_adv_basis: size of triangular part = 128
Solving LP relaxation...
0: objval = 8.580000000e+03 infeas = 1.000000000e+00 (0)
60: objval = 2.750607143e+03 infeas = 0.000000000e+00 (1)
* 60: objval = 2.750607143e+03 infeas = 0.000000000e+00 (1)
* 66: objval = 2.748345238e+03 infeas = 0.000000000e+00 (0)
OPTIMAL SOLUTION FOUND
Creating the conflict graph...
The conflict graph is either empty or too big
Generating cutting planes...
& 66: obj = 2.748345238e+03 frac = 53 cuts = 0 (0)
& 66: obj = 2.748345238e+03 frac = 53 cuts = 0 (0)
Integer optimization begins...
+ 66: mip = not found yet >= -inf (1; 0)
Gomory's cuts enabled
MIR cuts enabled
+ 936: >>>>> 7.430000000e+03 >= 7.144570915e+03 3.8% (41; 0)
+ 9213: >>>>> 7.390000000e+03 >= 7.263696178e+03 1.7% (509; 34)
+ 11681: >>>>> 7.370000000e+03 >= 7.284559348e+03 1.2% (449; 307)
+ 16050: >>>>> 7.360000000e+03 >= 7.332315412e+03 0.4% (288; 681)
+ 16236: >>>>> 7.350000000e+03 >= 7.334711878e+03 0.2% (178; 899)
+ 16377: mip = 7.350000000e+03 >= tree is empty 0.0% (0; 1449)
INTEGER OPTIMAL SOLUTION FOUND
Time used: 8.0 secs
Memory used: 2.0 Mb (2075158 bytes)
lpx_read_freemps: reading problem data from `./Problemes/pp08a.mps'...
lpx_read_freemps: problem pp08a
lpx_read_freemps: 137 rows, 240 columns, 656 non-zeros
lpx_read_freemps: 64 integer columns, all of which are binary
lpx_read_freemps: 657 records were read
ipp_basic_tech: 1 row(s) and 0 column(s) removed
ipp_reduce_bnds: 2 pass(es) made, 64 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 136 rows, 240 columns, 480 non-zeros
lpx_intopt: 64 integer columns, all of which are binary
lpx_adv_basis: size of triangular part = 128
Solving LP relaxation...
0: objval = 8.580000000e+03 infeas = 1.000000000e+00 (0)
60: objval = 2.750607143e+03 infeas = 0.000000000e+00 (1)
* 60: objval = 2.750607143e+03 infeas = 0.000000000e+00 (1)
* 67: objval = 2.748345238e+03 infeas = 0.000000000e+00 (0)
OPTIMAL SOLUTION FOUND
Creating the conflict graph...
The conflict graph is either empty or too big
Generating cutting planes...
& 67: obj = 2.748345238e+03 frac = 52 cuts = 0 (0)
& 67: obj = 2.748345238e+03 frac = 52 cuts = 0 (0)
Integer optimization begins...
+ 67: mip = not found yet >= -inf (1; 0)
Gomory's cuts enabled
MIR cuts enabled
+ 884: >>>>> 7.620000000e+03 >= 7.144497802e+03 6.2% (38; 0)
+ 1472: >>>>> 7.530000000e+03 >= 7.182610473e+03 4.6% (102; 2)
+ 5713: >>>>> 7.470000000e+03 >= 7.252173033e+03 2.9% (410; 35)
+ 8034: >>>>> 7.400000000e+03 >= 7.268312618e+03 1.8% (468; 172)
+ 9680: >>>>> 7.350000000e+03 >= 7.276647778e+03 1.0% (379; 491)
+ 13155: mip = 7.350000000e+03 >= tree is empty 0.0% (0; 1445)
INTEGER OPTIMAL SOLUTION FOUND
Time used: 5.0 secs
Memory used: 0.0 Mb (0 bytes)
- [Help-glpk] different executions on different platforms,
François Galea <=