Re: [Help-glpk] Why I get different results when I run lpx_std_basis before simplex?

[Andrew Makhorin]

> Just run fbavari pp.freemps if you have perl glpk installed.

> If one uncomment $lp->adv_basis, one will get different results. 

> Another question: 

> Way I,

> load model
> for loop
>      change obj coef 
>      simplex
> end

> Way II,

> for loop
>     load model
>     change obj coef 
>     simplex
> end

> This two ways will bring different results. Anyone know that?

Because your instance has multiple optimal solutions, that is
indicated by zero reduced cost of non-basic variables; so in one
case the solver finds one optimal solution while in other case it
finds another depending on which the starting basis is used.