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## Re: [Help-glpk] Sorting Vars?

**From**: |
Michael Hennebry |

**Subject**: |
Re: [Help-glpk] Sorting Vars? |

**Date**: |
Sat, 9 Feb 2008 11:38:15 -0600 (CST) |

On Sat, 9 Feb 2008, Daniel Reckhard wrote:
>* after specifying a 3-dimensional array of vars [1] in my model file I am*
>* surprised to see that this array appears to be unsorted [2]. That is*
>* very annoying as in the C API vars are always referenced by index [3].*
>
>* So, to calculate a valid index from a given l, p and b [4] the array has*
>* to be sorted! Is there any way to do that? Alternatively is there a*
>* function which returns the var's index for a given name?*
>
>* Because if sorting doesn't work and there is no such function I'll have*
>* to write it myself. I.e. parse the problem file into a 3 dimensional*
>* array in C with the mixed up index number as value. And that's really*
>* ugly and time-consuming. :(*
Unless the documentation says so,
I wouldn't assume that lpx_print_prob prints in index order.
Since you have only one array and no other variables, I think you are in luck.
Difficulties like yours are the reason I usually access
solvers through their APIs instead of a modelling language.
>* [1] var x{l in Line, j in Products, b in 0..Bucket} >= 0;*
>
>* [2] Excerpt retreived with lpx_print_prob*
>* ...*
>* 4 x[1,1,2]*
>* 4 x[1,1,3]*
>* 10 x[2,1,0]*
>* 2 x[2,1,1]*
>* 2 x[2,1,2]*
>* 2 x[2,1,3]*
>* 3 x[1,1,4]*
--
Michael address@hidden
"Those parts of the system that you can hit with a hammer (not advised)
are called Hardware; those program instructions that you can only
curse at are called Software."