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## RE: [Help-glpk] Multi-ranged column bounds

 From: Ariel Daliot Subject: RE: [Help-glpk] Multi-ranged column bounds Date: Thu, 11 Feb 2010 17:53:22 +0200

```Thanks for the reply.
The trick of using an auxiliary binary  variable z:
5 * z <= x <= 10 * z
to make x become semi-continuous 5<=x<=10 or x=0, effectively turns a
continuous problem into a mixed integer problem with all its woes.
Any idea how to circumvent the execution time accompanying this? Does anyone
know if semi-continuous variables is planned to be modeled in GLPK sometimes?
Thanks a lot,
Ariel

-----Original Message-----
Sent: Thursday, February 11, 2010 3:17 PM
Subject: Re: [Help-glpk] Multi-ranged column bounds

Hi,
you are talking about semi-continuous variables
(http://lpsolve.sourceforge.net/5.5/semi-cont.htm). They are not modelled in
GLPK but you can simulate them using the approach explained here:

------------------------------

Message: 4
Date: Thu, 11 Feb 2010 14:34:46 +0200
Subject: [Help-glpk] Multi-ranged column bounds
Message-ID:

Content-Type: text/plain; charset="us-ascii"

Hello all,

I am trying to solve a problem using glpk 4.42.
I need the continuously valued columns to upper and lower bounds but also to be
able to have a single integer value out of this bound.
More specifically, I need all the columns Xi to be bounded by 6=< Xi =<16 but I
also want Xi=0 to be a possible value for the variables.
This is how I set the range:

glp_set_col_kind(lp, Xi, GLP_CV);
glp_set_col_bnds(lp, Xi, GLP_DB, 6.0, 16.0);

but how can I add Xi=0 to the allowed range?

Ariel

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