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## [Help-glpk] Re: How to make consecutive variables take a certain value?

 From: ican.ozgur Subject: [Help-glpk] Re: How to make consecutive variables take a certain value? Date: Fri, 30 Nov 2007 10:40:41 +0200 User-agent: KMail/1.9.6

```On Friday 30 November 2007 07:32:15 Oscar Gustafsson wrote:
> On Thu, 29 Nov 2007, Michael Hennebry wrote:
> > Mathematically correct, but one should go for a tighter linear
> > relaxation. x[d,h]<=x[d,h+1]
> > x[d,h]<=x[d,h+2]
> > With this formulation, the latter constraint is redundant.
> > x[d,h]<=x[d,h+1] where d indexes a day and h and h+1 index hours.
>
> Won't this force all the remaining hours of the day to be one?
>
> On the other hand as the question is formulated it is supposedly what is
> going to happen.
>
> My guess without knowing the context is that it might be better to imply
> the three our booking rule in the resource constraints instead of forcing
> the next two variables to be one, as this will lead to all preceeding
> variables to be one. An alternative might be to have two types of
> variables, one that considers the "original" one and one with variables
> that are one based on the original ones.
>
> But considering it is 6:30 in the morning I may be really out of line
> here.
>
> Regards
>
> Oscar

The problem is a timetabling problem, and indeed there are three
indices "x_dhc" standing for day,hours and classroom and there are sessions
which has 2, 3 and 4 hours length of duration .I'm trying to allocate
available hours of every classroom in a week.

--
O. Ican

```