Re: [Help-glpk] type of variables

[Nigel Galloway]

That is a good start.

 

GLPK can use this as a biasis for integer optimisation. The output from simplex is a solution based on a continuous number system. You want a discreet solution. It would be nice if just rounding the continuous solution to the nearest integer produced the answer. Usually it doesn't.

 

You must next call glp_intopt  using your simplex produced basis as the parameter.

 

To obtain the answer you must then use glp_mip_col_val for individual columns, or glp_print_mip for the entire solution. You might like to also call glp_print_sol and compare how close the actual values in glp_print_mip are to the values in glp_print_sol if you just rounded them. 

 

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Nigel Galloway

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On Sep 5 ’11, "name name" <address@hidden> wrote:

I solve it with

  glp_simplex(lp, parm)  routine

On Mon, Sep 5, 2011 at 2:54 PM, Nigel Galloway <address@hidden> wrote:

The question is how do you solve the problem, and how do you obtain the solution.

 

When you make all these columns binary you have a Diophantine Equation. GLPK can solve these, though there are other ways which may be better.

 

GLPK will first solve it as a linear problem. It is then necessary to perform Integer Optimization.

 

Having done this there are different routines to obtain the integer optimal solution as opposed to the linear solution.

--

Nigel Galloway

address@hidden

 

 

On Mon, 05 Sep 2011 14:26 +0200, "name name" <address@hidden> wrote:

On Mon, Sep 5, 2011 at 1:18 PM, Nigel Galloway <address@hidden> wrote:

Do you obtain this value with GLPK.glp_get_mip_col_val ?

no with .glp_set_col_kind
Even if the type of variable is binary Lp give non integer value
 

--

Nigel Galloway

address@hidden

 

On Mon, 05 Sep 2011 09:52 +0200, "name name" <address@hidden> wrote:

 

Hello,

I have a very strange problem

I solve un Lp problem but the and the value of my  variables are not ineger I got x(0,1)=0.2... even thaught when I print the type of my variables I got 3 coresponding to type binary( I got type to binary for all variables with GLPK.glp_set_col_kind(lp, i, GLPKConstants.GLP_BV)).

Can you tell my where the problem could be?

Thank you

Onor

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