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Re: [Help-glpk] [Fwd: glpsol not converging]


From: Xypron
Subject: Re: [Help-glpk] [Fwd: glpsol not converging]
Date: Fri, 27 Jul 2012 00:19:41 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.5) Gecko/20120624 Icedove/10.0.5

Hello Narendra,

>> + 34748: mip =     not found yet >=   1.058800000e+04        (1; 0)
>> TIME LIMIT EXCEEDED; SEARCH TERMINATED

you have to choose a time limit which is high enough to have a MIP solution.

Best regards

Xypron

On 26.07.2012 23:40, Narendra Devta-Prasanna wrote:
Hi Xypron,

When I try with "--tmlim 100", the printf commands just print null strings for the variables in the ILP. The output file does not have any values assigned for the variables as well. In the end of the output file, I see this:

Integer feasibility conditions:

KKT.PE: max.abs.err = 0.00e+00 on row 0
        max.rel.err = 0.00e+00 on row 0
        High quality

KKT.PB: max.abs.err = 1.60e+01 on row 34
        max.rel.err = 9.41e-01 on row 34
        SOLUTION IS INFEASIBLE

End of output

The log file has this information:

* 29500: obj =   1.058950243e+04  infeas =  2.460e-13 (2)
* 29725: obj =   1.058800000e+04  infeas =  6.601e-13 (2)
OPTIMAL SOLUTION FOUND
Integer optimization begins...
+ 29725: mip =     not found yet >=              -inf        (1; 0)
| 32500: obj =   1.058800000e+04  infeas =  3.451e-10 (2)
| 33000: obj =   1.058800000e+04  infeas =  4.318e-10 (2)
| 33500: obj =   1.058800000e+04  infeas =  4.521e-10 (2)
| 34000: obj =   1.058800000e+04  infeas =  5.004e-10 (2)
| 34500: obj =   1.058800000e+04  infeas =  2.476e-10 (2)
| 34748: obj =   1.058800000e+04  infeas =  4.083e-10 (2)
+ 34748: mip =     not found yet >=   1.058800000e+04        (1; 0)
+ 34748: mip =     not found yet >=   1.058800000e+04        (1; 0)
TIME LIMIT EXCEEDED; SEARCH TERMINATED
Time used:   120.8 secs
Memory used: 160.7 Mb (168467811 bytes)
Writing MIP solution to `./glpk_ex3/ex3_TAM_IP_glpk_step1.out'...

Is it possible to print out the "OPTIMAL SOLUTION FOUND" in some way? The actual routing problem I am solving is a non-linear problem which I am modeling as a ILP to get a solution which is anyways not optimal for the problem but happens to be much better than a "random" solution.

So, for the ILP, even if it is not an optimal solution, it is acceptable for my situation.

Really appreciate your suggestions regarding this...

Thanks & Regards,
-Narendra


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