[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Bug-glpk] [Fwd: Simplex termination 32 vs. 64 bit]
From: |
glpk xypron |
Subject: |
Re: [Bug-glpk] [Fwd: Simplex termination 32 vs. 64 bit] |
Date: |
Sun, 08 Apr 2012 10:53:00 +0200 |
On Windows 32bit the problem is also solved after a few iterations. Hence this
is not a problem depending on the bitness of the system.
On Linux 32 bit solving problem is not completed with default settings. But the
problem is solved at short notice with:
glpsol --lp input.cplex --first
Best regards
Xypron
> -------- Forwarded Message --------
> From: Horst Schirmeier <address@hidden>
> To: address@hidden
> Subject: Simplex termination 32 vs. 64 bit
> Date: Sat, 7 Apr 2012 18:56:09 +0200
>
> Hi,
>
> for the attached CPLEX-format ILP I'm observing a different termination
> behaviour on 32-Bit (doesn't terminate within the observed time frame of
> several hours) vs. 64-Bit (terminates after 0.4s) Linux. I'm running
> unpatched glpsol 4.47 (.tar.gz taken from gnu.org, built from sources)
> on Debian 6.0:
>
> Debian 6.0, 32-Bit:
> $ glpsol --lp input.cplex
> GLPSOL: GLPK LP/MIP Solver, v4.47
> Parameter(s) specified in the command line:
> --lp input.cplex
> Reading problem data from `input.cplex'...
> 332 rows, 2301 columns, 6903 non-zeros
> 2301 integer variables, all of which are binary
> 7228 lines were read
> GLPK Integer Optimizer, v4.47
> 332 rows, 2301 columns, 6903 non-zeros
> 2301 integer variables, all of which are binary
> Preprocessing...
> 314 rows, 2301 columns, 4602 non-zeros
> 2301 integer variables, all of which are binary
> Scaling...
> A: min|aij| = 1.000e+00 max|aij| = 3.000e+00 ratio = 3.000e+00
> Problem data seem to be well scaled
> Constructing initial basis...
> Size of triangular part = 314
> Solving LP relaxation...
> GLPK Simplex Optimizer, v4.47
> 314 rows, 2301 columns, 4602 non-zeros
> 0: obj = 3.372000000e+03 infeas = 2.430e+02 (0)
> * 315: obj = 3.153000000e+03 infeas = 0.000e+00 (0)
> * 500: obj = 1.321000000e+03 infeas = 1.092e-15 (0)
> * 851: obj = 5.020000000e+02 infeas = 7.401e-17 (0)
> OPTIMAL SOLUTION FOUND
> Integer optimization begins...
> + 851: mip = not found yet >= -inf (1; 0)
> + 1437: >>>>> 5.040000000e+02 >= 5.020000000e+02 0.4% (50; 0)
> + 1631: >>>>> 5.030000000e+02 >= 5.020000000e+02 0.2% (65; 21)
> + 40041: mip = 5.030000000e+02 >= 5.020000000e+02 0.2% (51; 2232)
> + 76140: mip = 5.030000000e+02 >= 5.020000000e+02 0.2% (137; 4202)
> +116304: mip = 5.030000000e+02 >= 5.020000000e+02 0.2% (116; 6415)
> [... continues for hours without ever terminating ...]
>
> Debian 6.0, 64-Bit:
> $ glpsol --lp input.cplex
> GLPSOL: GLPK LP/MIP Solver, v4.47
> Parameter(s) specified in the command line:
> --lp input.cplex
> Reading problem data from `input.cplex'...
> 332 rows, 2301 columns, 6903 non-zeros
> 2301 integer variables, all of which are binary
> 7228 lines were read
> GLPK Integer Optimizer, v4.47
> 332 rows, 2301 columns, 6903 non-zeros
> 2301 integer variables, all of which are binary
> Preprocessing...
> 314 rows, 2301 columns, 4602 non-zeros
> 2301 integer variables, all of which are binary
> Scaling...
> A: min|aij| = 1.000e+00 max|aij| = 3.000e+00 ratio = 3.000e+00
> Problem data seem to be well scaled
> Constructing initial basis...
> Size of triangular part = 314
> Solving LP relaxation...
> GLPK Simplex Optimizer, v4.47
> 314 rows, 2301 columns, 4602 non-zeros
> 0: obj = 3.372000000e+03 infeas = 2.430e+02 (0)
> * 315: obj = 3.153000000e+03 infeas = 0.000e+00 (0)
> * 500: obj = 1.488000000e+03 infeas = 0.000e+00 (0)
> * 844: obj = 5.020000000e+02 infeas = 8.327e-17 (0)
> OPTIMAL SOLUTION FOUND
> Integer optimization begins...
> + 844: mip = not found yet >= -inf (1; 0)
> + 2394: >>>>> 5.040000000e+02 >= 5.020000000e+02 0.4% (42; 0)
> + 3560: >>>>> 5.030000000e+02 >= 5.030000000e+02 0.0% (37; 88)
> + 3560: mip = 5.030000000e+02 >= tree is empty 0.0% (0; 171)
> INTEGER OPTIMAL SOLUTION FOUND
> Time used: 0.4 secs
> Memory used: 2.1 Mb (2252288 bytes)
>
> The input data is attached to this email. Is it somewhat malformed, or
> did I indeed step on a GLPK bug?
>
> Kind regards,
> Horst Schirmeier
>
--
Follow me at http://twitter.com/#!/xypron
Empfehlen Sie GMX DSL Ihren Freunden und Bekannten und wir
belohnen Sie mit bis zu 50,- Euro! https://freundschaftswerbung.gmx.de