[gecode-users] task end times in cululative/unary constraints

[Kish Shen]

Hi,

In most versions of Gecode's cumulative and unary constraints, you need 
to provide the start, duration and end times for tasks. For the ECLiPSe 
cumulative and unary constraints, you only need to provide the start and 
duration times. I understand that having the end times for task allows 
for more opportunities for propagation, but are they needed (or more 
precisely, are the extra constraints end = start + duration needed). if 
the end times are not used anywhere.

The reason I am asking is that in the ECLiPSe interface to Gecode, one 
of the aim is to provide compatibility to existing ECLiPSe code, so this 
means providing cumulative/unary constraints with flexible durations, 
but without end times, which is what ECLiPSe has. For these constraints, 
the user would have no access to the end times, but currently I still 
post the extra constraints end = start + duration for each task, as the 
Gecode call requires the end times, and MPG suggest that these 
constraints should be posted. But when I was looking at the code 
yesterday, I started to wonder if this makes sense if the user cannot 
see (and so cannot post constraints that will affect) the end times. So 
my question is, does it make sense to post these constraints under these 
conditions?

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.