A function returning the smallest element from a set would be very useful
for me too.
anything better than the the O(n^2) suggestion would be great....
*set F := setof{ s in S : forall{u in S} s <= u } s;*
Can this be implemented in GLPK ?
On Thu, Oct 22, 2009 at 3:05 PM, xypron <[email protected]> wrote:
>
> Hello
>
> >> have a set MBC.
> >> Now I need the restriktion, y[x]=0 where x is just the first element of
> >> the MBC.
>
> sets in GLPK are unordered. Hence the first element cannot be accessed. Of
> cause you could define a parameter with the value of the first element.
>
> Determining a set containing the smallest element of a given set is
> possible.
> See example below.
>
> Best regards
>
> Xypron
>
> # some set
> set S;
> # set of the smallest element in S
> # GLPK is inefficient here, needing O(n^2) time!
> set F := setof{ s in S : forall{u in S} s <= u } s;
> # variable
> var y{s in S}, >= 0, <=1;
> # some objective
> maximize obj :
> sum{s in S} y[s];
> # constraint for the smallest element in S
> s.t. c1{s in F} :
> y[s] = 0;
> # display constraint
> display c1;
> # initialization
> data;
> set S := the quick brown fox jumps over a lazy dog;
>
> --
> View this message in context:
> http://www.nabble.com/First-element-of-the-set-tp26010502p26013668.html
> Sent from the Gnu - GLPK - Help mailing list archive at Nabble.com.
>
>
>
> _______________________________________________
> Help-glpk mailing list
> [email protected]
> http://lists.gnu.org/mailman/listinfo/help-glpk
>
--
=============================================================
Haroldo Gambini Santos
Computing Department - Universidade Federal de Ouro Preto - UFOP
email: haroldo [at ] iceb.ufop.br
home/research page: www.decom.ufop.br/haroldo/
"Computer science is no more about computers than astronomy
is about telescopes." Edsger Dijkstra
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