Re: [Help-glpk] Sorting Vars?

[Andrew Makhorin]

> 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!

Not necessary. It depends on implementation. Besides, arrays can be
sparse, in which case sorting is useless.

>  Is there any way to do that? Alternatively is there a 
> function which returns the var's index for a given name?

Yes. It is glp_find_col.

> 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. :(

> [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]
> ...

> [3] E.g. lpx_set_mat_row needs a one-dimensional index to reference the 
> according variable.

> [4] E.g. index = l * P_max * B_max + p * B_max + b;

> Thanks for your time,