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Re: [Help-glpk] How TO interpret information from results
From: |
Andrew Makhorin |
Subject: |
Re: [Help-glpk] How TO interpret information from results |
Date: |
Wed, 15 Mar 2006 19:58:31 +0300 |
> I would like to ask that from the result output
> of the model file for example shown below i
> would like to get information that what exactly is
> what
> 1. What does "St" stand for n what are "B" "NL"
> denoted.
> 2. What does it mean when the marginal value is "positive" and
> "esp" and what if its "Negative value"
> Problem: tspmatrixfin
> Rows: 71
> Columns: 191
> Non-zeros: 850
> Status: OPTIMAL
> Objective: path = 4002.331 (MINimum)
>
> No. Row name St Activity Lower bound Upper bound Marginal
> ------ ------------ -- ------------- ------------- -------------
> -------------
> 1 path B 4002.33
> 2 Travelled_distance[0]
> NL 2 2
> 263.609
> 3 Travelled_distance[1]
> NL 2 3
> esp
> 4 Travelled_distance[2]
> NL 2 2
> -83.12
For rows:
St = B means the corresponding constraint is inactive, i.e. its
auxiliary variable is basic.
St = NL means the corresponding constraint is active, i.e. its
auxiliary variable is non-basic (on the lower bound).
If marginal value is d > 0, the corresponding constraint is active
and increasing its lower bound by one will lead to increasing the
objective function by +d (until the basis will have been changed).
Analogously, if d < 0, the corresponding constraint is active and
decreasing its upper bound by one will lead to increasing the
objective by -d.
If marginal value is printed as eps, this means that its value is
close to zero, i.e. the corresponding solution is degenerative.
P.S. I recommend you to consult any textbook on linear programming.
Andrew Makhorin