Hi,
I am looking at the unary scheduling constraints, as I have just added
them to the ECLiPSe gecode interface. ECLiPSe has both unary and
cumulative constraints, which were added some time ago (more than 10
years ago now, I think), and for the unary constraint, there is a
version with ordering booleans, where each pair of task has a 0/1 domain
variable (BoolVar for gecode) associated with it, which specify the
order of the pair of task (if i is before j or j before i for pair i,j).
This seems to be very useful, because it can used to specify ordering if
required, or be used in search to try the different orderings.
I guess for gecode, you would need to post extra reified constraints
specifying the ordering? Does it make sense to move this into the unary
constraint?
I was also looking at the global constraint catalog, to see if they have
a unary constraint with ordering. I found disj, which specify ordering
in a different way: for each task, there is a set variable that
gives/specify the tasks that happen earlier, and a variable position
that gives the absolute order of the task. The description then mention
that the algorithm for shaving the position attribute is implemented in
gecode. Is this in the unary constraint? Is it used internally? I can't
see any ordering information that can be accessed from the outside in
the description of the unary constraint, or have I missed something?
Thanks and cheers,
Kish
--
This e-mail may contain confidential and privileged material for the
sole use of the intended recipient. Any review, use, distribution or
disclosure by others is strictly prohibited. If you are not the intended
recipient (or authorized to receive for the recipient), please contact
the sender by reply e-mail and delete all copies of this message.
Cisco Systems Limited (Company Number: 02558939), is registered in
England and Wales with its registered office at 1 Callaghan Square,
Cardiff, South Glamorgan CF10 5BT.
_______________________________________________
Gecode users mailing list
[email protected]
https://www.gecode.org/mailman/listinfo/gecode-users
