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Re: [Help-glpk] How to provide to the GLPK MIP solver a integer feasible

From: Giorgio Sartor
Subject: Re: [Help-glpk] How to provide to the GLPK MIP solver a integer feasible solution
Date: Tue, 9 Apr 2013 15:19:49 +0200

Thanks Raniere and Haroldo...

but my problem is that GLP_IHEUR is always OFF (or FALSE) because the presolver always finds the optimal solution to the LP relaxation, so the callback is never "called". How can I bypass that problem?


2013/4/9 Haroldo Santos <address@hidden>
Yes, it can be done using callbacks, but it would be nice if GLPK could:

- read from command line (glpksol)
- enter in MathProg

On Mon, Apr 8, 2013 at 10:36 PM, Raniere Silva <address@hidden> wrote:
Hi Giorgio,

> I have a model to which I can provide a initial feasible solution.
> How can I do that?

I do long time ago (about 3 years).

> Initially I tried with glp_read_mip:

I didn't use that. Hope that some one can help you with that.

> The second attempt was with the callback routine:
> void callback(glp_tree *tree, void *info){
>     switch(glp_ios_reason(tree)) {
>         case GLP_IHEUR: glp_ios_heur_sol(tree, initsol);break;
>         default: break;
>     }
> }
> where initsol was the integer feasible array solution. The code was:
> ...
> glp_iocp parm;
> glp_init_iocp(&parm);
> parm.cb_func = callback;
> glp_simplex(mip, NULL);
> glp_intopt(lp, &parm)
> ...

I used the callack function below:

void callback(glp_tree *tree, void *info){
    if(glp_ios_reason(tree) == GLP_IHEUR && glp_ios_curr_node(tree) == 1){
        glp_ios_heur_sol(tree, info);
    }   /* -----  end if  ----- */

    return ;


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Haroldo Gambini Santos
Computing Department
Universidade Federal de Ouro Preto - UFOP
email: haroldo [at ]
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