[gecode-users] Graph Connectivity Problem

[Christian Schulte]

Hi Halit,

unfortunately there is no predefined constraint for that. There are two
options for pulling that of: use reification or implement a propagator to
enforce connectedness. I think I haven't seen a special constraint for that
in any system.

Anyway, you might want to not encode that as 0/1 but set variables: in a
sequence of n variables x, the set for x_n contains the adjacent nodes. That
should be more efficient.

If you are interested in building a propagator, that should be pretty easy.
The implementation of the circuit constraint will give much of what needs to
be done.

Christian

--
Christian Schulte, www.ict.kth.se/~cschulte/


-----Original Message-----
From: users-bounces at gecode.org [mailto:users-bounces at gecode.org] On Behalf
Of Halit Erdogan
Sent: Monday, May 18, 2009 6:42 PM
To: users at gecode.org
Subject: [gecode-users] Graph Connectivity Problem

Dear All,

Although it seems a very common problem I could not find any  
information on forcing graph connectedness neither in documentation  
nor in the web archive.

The problem is: I have a matrix "m" representing an undirected graph.  
m(i,j) = 1 means there is an edge between the vertices i and j. I want  
m to represent a connected graph (every pair of distinct vertices in  
the graph ( (i,j) in m) is connected through some path). How can I  
write this as a constraint in gecode?

thanks in advance,
-halit



-- 
Halit Erdogan
B.S. Sabanci University
Computer Science and Engineering

email   : halit at su.sabanciuniv.edu
phone   : +90 505 476 75 76
webpage : http://students.sabanciuniv.edu/~halit/

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