Unfortunately, the last solution may not work if profit was defined as
a set in the model file, ie:
set profit;
{ j in profit, i in profit: j>i} # will not work
since a set has no order. Instead, the set needs to be ordered.
set profit ordered # use the ampl keyword ordered
Then you can use the ord() function to do the comparison:
{ j in profit, i in profit: ord(j)>ord(i)}
This should do the trick.
Cheers,
Dan
On Oct 22, 4:15 pm, Vikas Phanse <
phanse...@...> wrote:
> How about defining set as follows:
>
> { j in profit, i in profit: j>i}
>
> --- On Thu, 10/22/09, Gideon <
gideon.mbiydzen...@...> wrote:
>
> From: Gideon <
gideon.mbiydzen...@...>
> Subject: [AMPL 2903] Re: Summation Index Notation for i > j
> To:
ampl@...
> Date: Thursday, October 22, 2009, 7:27 AM
>
> One labourious way is in the way you treat your data i.e. remove
> symmetry by entrying zero values on the other side of the diagonal and
> allow your sum over the entire metric
>
> /Gideon
>
> Emily Heeb skrev:
>
> > I have a quick syntax question regarding AMPL programming. If I have a
> > set, say {profit} and I want to do an operation such as:
>
> > sum {j in profit, i in profit} 2 * Covariance [j,i]
>
> > but ONLY for j > i.
>
> > How do I incorporate this constraint into the model?
>
> >
>
> --
> Gideon Mbiydzenyuy
> PhD Candidate, e-Transactions,
>
> Avdelningen för programvarusystem, Dept. of Systems and Software Eng.,
> Sektionen för teknik School of Engineering,
> Blekinge Tekniska Högskola Blekinge Institute of Technology
>
> Box 214
> SE - 374 24 Karlshamn
> Sweden
>
> Tel: +46 454 385904 (Karlshamn)
> Tel: +46 457 385897 (Ronneby)
> Mob: +46 768 856713
> Fax: +46 454 191 04 (Karlshamn)
> Homepage:
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