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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