Re: [Help-glpk] Rounding Problem

[glpk xypron]

Hello

GLPK uses a tolerance internally. Please change your tests, e.g.

fabs(nx) < .0001

Best regards

Xypron


-------- Original-Nachricht --------
> Datum: Wed, 28 Apr 2010 17:26:16 +0300
> Von: Volkan YAZICI <address@hidden>
> An: address@hidden
> Betreff: [Help-glpk] Rounding Problem

> Hi,
> 
> I get below solutions
> 
>   (gdb) p glp_get_col_val(lp, 'n', 7)
>   $4 = 0
>   (gdb) p glp_get_col_val(lp, 'c', 0)
>   $5 = 1
>   (gdb) p glp_get_col_val(lp, 'c', 1)
>   $6 = 1
>   (gdb) p glp_get_col_val(lp, 'c', 2)
>   $7 = 1
>   (gdb) p glp_get_col_val(lp, 'c', 4)
>   $8 = 1.0000000000000002
> 
> for the following constraint.
> 
>   n7 - c0 - c1 - c2 - c4 >= -4
> 
> n7 should be greater than 0, but because of rounding errors it passes
> the constraint check.
> 
>   (gdb) p (0 - 1 - 1 - 1 - 1.0000000000000002) >= -4
>   1
> 
> What's the recommended way of solving such problems? I looked at ml
> archives and found out that people use glp_scale_prob() method. But for
> my particular case -- where I just check if (nx == 0.0) and if (cx ==
> 1.0) -- I couldn't figure out which option to use with glp_scale_prob()
> method. Any ideas?
> 
> 
> Regards.
> 
> 
> _______________________________________________
> Help-glpk mailing list
> address@hidden
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