c2s.computer@interbusiness.it (Gianni Alberti) writes:
> I like to know what is wrong in the following program:
> [...]
> The difference is that I want to use a global variable for distribution : what is my fault ?
The problem is precisely that you have global variables in your search
problem. Suppose you have global boolean FD variable X and in space S
you speculatively constrain X=0. Is S a solution? Well, the answer
is that you can't know that yet because X remains globally
undetermined. Suppose you subsequently decided to add the global
constraint X=1, then S would become inconsistent, i.e. failed.
In such a case, we say that S is not `stable': it suspends on a global
variable. We can only decide that S is a solution or not when
sufficient global information becomes available to decide whether the
local constraints on global variables are entailed or disentailed by
the global constraints.
In a search problem, all the variables of your CSP must be local
variables.
Cheers,
-- Dr. Denys Duchier Denys.Duchier@ps.uni-sb.de Forschungsbereich Programmiersysteme (Programming Systems Lab) Universitaet des Saarlandes, Geb. 45 http://www.ps.uni-sb.de/~duchier Postfach 15 11 50 Phone: +49 681 302 5618 66041 Saarbruecken, Germany Fax: +49 681 302 5615 - Please send submissions to users@mozart-oz.org and administriva mail to users-request@mozart-oz.org. The Mozart Oz web site is at http://www.mozart-oz.org/.