help-glpk
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## Re: [Help-glpk] Multivariate problem

 From: Xypron Subject: Re: [Help-glpk] Multivariate problem Date: Sat, 03 Oct 2009 19:22:12 +0200 User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.1.23) Gecko/20090823 SeaMonkey/1.1.18

```Hello Juliana,

```
For a reference see the API documentation in doc/glpk.pdf in the distribution tarball available at ftp://ftp.gnu.org/gnu/glpk/glpk-4.39.tar.gz Have a look at the examples the examples folder and in glpk-java available at http://glpk-java.sourceforge.net/
```Consider using modeling language GNU Mathprog available in GLPK.

sum[i=m to N] x_i((a_i) + (b_i*y_i))  + sum[i=1 to N] b_i*y_i
```
is not a linear term because it contains the product of two variables x_i * y_i.
```
```
If you want to use a MILP solver like GLPK you will have to reformulate your problem, e.g.
```
maximize obj :
sum{i in m..N} w[i] + sum{i in 1..N} b[i]*y[i];

s.t. c1{i in m..N} :
w[i] <= a[i] + b[i] * y[i];
s.t. c2{i in m..N} :
w[i] <= x[i] * M;

Best regards

Xypron

Juliana Freitag wrote:
```
Hi everybody,
```  is it possible to model the function below using GLPK API?

sum[i=m to N] x_i((a_i) + (b_i*y_i))  + sum[i=1 to N] b_i*y_i

a and b are constants
x is a binary variable
y is a integer variable

```
Thank you, Juliana.
```
``` Roy.tar.gz
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