> The optimizer takes as input (among others) a list of forbiden allocations
> that should be generated based on some user-provided rules.
to me you mean "generating an allocation plan".
drools-planner is for you, especially if your users want to define more complex rules.
Actually, there is a optimization-team that already worked on that and came up with their own solution.
They also evaluated Drool-planner for the "planning" part but went another direction for several reasons.
I am only working here into transforming the complex user-filled rules into "forbid" pairs as an input
to the optimizer.
I might use drools-planner for this.
and here it sounds like a service that has a stream to consume ?
then just write rules, put a session in a separate thread, and send him your stream as input.
You can even use drools-fusion time operators.
No a stream, but yes, this is a service that will stay up and act as a method :
Return the list of forbids for a given list of activities and resources.
I will pretty much build a knowledge base, and then, from time to time, feed it with data, fire the rules and
look for forbid pairs.
> Performance constraints
> Here are some rough hints about the volumetry of the problem :
> * 1000 activities
> * 200 resources
> * 50 rules
>
> I need the forbidden allocations to be generated in under a minute.
is it the due time for you plan ?
This is a due time, for an acceptable response time to the user.
> Instead, I would try to match the resources and the activities separately
> on each rule (each side of the rule), and then assemble the couples that
> match at least one common rule.
RETE will do that for you
> Also, I would add some counter on each rule that would auto increment upon
> each match, in order to apply first the rules that match often.
If there is a session in a thread, ie maintaining its kownledge over time,
RETE will do that for you, by propagating only the updates to the matching rules (forward chaining).
Not sure if I get it.
If I have two rule A and B that may produce the same forbid pairs, I want to produce this pair only once.
For that, I will use inference and produce a :
insert(new Forbid(ressource, activity))
Then, in each rule, I will check that this forbid is not already present.
So my question is :
Will Drools "learn" from preivous processings and "learn" that rule A matches more often than rule B ? And so will it promote A to be processed first ?
Even if I flush the working memory between two calls ?
If you speak about optimisation using local search, drools-planner will do that for you (by using the previous, may be with adding so custom moves generators).
> QuestionsIs the engine of Drools smart enought for that ? Or is he even
> smarter ?
If the point is to process forbidden associations, yes, drools can be smarter than that.
I whould even say that drools shoud be used only if you want to do to more than that.
Hmm, yes, this is the dilemma :
I think that, for this particular problem, I could write an algorithm myself.
I am trying to understand how Drools works in its guts, to foresee if
it is a good investment for the future.
For example, we are beginning to think about neighborhood forbids,
to forbid pairs of allocations <<Res1, Act1>, <Res2, Act2>> ...
> Do you have an example of Drools being used in a similar problem with
> success ?
optim : drools-planner and its cloud balancing sample
real-time stream : look at drools-fusion samples and also drools-expert doc (to get the basis of what rules can do)
Thanks for those hints.
Brgds,
Raphael