Re: [Bug-glpk] [Fwd: Simplex termination 32 vs. 64 bit]

[glpk xypron]

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
> 

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