On 25-06-14 12:58, DwProd . wrote:
Thanks a lot for your answer !
1) I don't think pillar based moves are what I'm looking for, except
if I can select a pillar based on a Problem Fact (its service in my
case) and then spread the different entities of the pillar on the
available hosts (basically setting possibly different planning
variables for the entities of the pillar).
2) cartesianProductMoveSelector seem more like it, but the number of
moves to combine is somewhat static is it not ? I can't for instance
specify in a Planning Entity (using a property) that its move should
be combined with n other moves of processes of the same type ?
That would be nearBySelection... (note: the name might change before I
implement).
You need to be able to tell optaplanner that processes of the same type
are "near" (~related) to each other and should be moved together.
As stated before, I am working on this for 6.2.
3) I feel like my usecase is complicated enough to have to resort to
that if there is no built in way to handle it... Does this work by
implementing a MoveListFactory, or a CompositeMove ? I don't think I
quite get the difference to be honest...
If you write a custom MoveListFactory (or MoveIteratorFactory), you
could still opt to go with the build-in moves (such as ChangeMove) or
combinations of those with CompositeMove. However, because those
build-in moves require reflection stuff (VariableDescriptor etc), it's
probably easier to just to write a domain-specific Move.
See the examples that have custom moves.
Thanks again for your time,
Cheers,
Woody
2014-06-25 9:37 GMT+02:00 Geoffrey De Smet <ge0ffrey.s...@gmail.com
<mailto:ge0ffrey.s...@gmail.com>>:
1) There's 2 course grained moves out of the box in 6.1.0.CR1:
pillarChangeMove and pillarSwapMove.
And in 6.1.0.CR1 they also include subpillars (which is important).
http://docs.jboss.org/drools/release/latest/optaplanner-docs/html_single/index.html#pillarChangeMoveSelector
Start with trying those.
2) Then look into cartesianProduct selection and mimic selection
(see docs).
The <cartesianProductMoveSelector> allows you to combine to
existing moves into a new one.
The mimic selection allows you to make sure that those 2 moves
change the same entity (if needed), but a different variable of
course.
I am working on nearBySelection for 6.2 to allow it to select 2
entities that are somehow "nearBy" to each other (for example in
the same service etc).
3) If the above don't help enough, there's always custom moves
(see docs): total freedom, but the devil is in the details :)
On 24-06-14 01:58, DwProd . wrote:
Hello there,
I'm pretty new to OptaPlanner, and I must say I'm really
impressed with the maturity of it all. Great software with a
great documentation !
I've been working on a variation of the Cloud Balancing example,
with a few differences, which make it look like the Machine
Reassignment problem as well :
- Some processes are already placed and are immovable (using a
Selection Filter checking a boolean property of the planning entity)
- The Computer (the planning variable) is nullable (basically
this is Multiple Muti-Dimensional Knapsack problem) which means I
added a soft constraint penalty for processes with a null host.
- Processes can only be of a few classes (which I called
services, a Problem Fact). Processes of a given service type have
a certain amount of required cpu and ram.
Taking these elements into account, I do get very good results
with OptaPlanner. However, the following constraints always put
me into a score trap :
- For some services, processes work in groups. For instance, if
groups are of size 3, having 7 processes is not any better than
having 6 processes. If there were already 2 processes (immovable
and placed), I should only add 4 processes and not 5, even if
there are enough resources. For this constraint, I have tried
using a rule (medium constraint) accumulating processes of that
service and using the modulo operator with the group size.
- Some services are dependant on one another. For instance, I
know that if I have n1 groups of processes of the service 1, I
require Math.ceil(2.5*n1) groups of processes of the service 2. I
have implemented this similarly with a medium constraint...
With any (or both) of these constraints, little to no processes
of the concerned services are added and I fail to reach a good
solution. I have tried benchmarking with several local search
methods and various parameters, but all give the same results...
I feel like the next logical step would be to used the often
mentioned in the documentation "Coarse Grained Moves" but I fail
to locate any simple example. The Nurse Rostering example seems
to use that technique to some extent but it seems like an overly
complicated example, is it not.
Thank you very much for reading this far, if you have any
question, guideline, or just a trick, I'd be absolutely delighted
to hear from you !
Cheers,
Woody
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