Op 24-07-12 23:14, Josef Bajada schreef:
Hi Geoffrey,
Thanks for your reply.
> Does it make sense to wait longer than 7 mins after task A
(presuming no other task forces occupies the user at that time)?
> Put differently: Can we say that the starting time of B =
Math.max((endTime of task before B), (endTime of task A + 7 minutes))?
> If we can say that, it's pointless to investigate the solutions
where task B starts 8 minutes after task A and the user doing no task
that last minute.
Yes, the starting time of B = Math.max((endTime of task before B),
(endTime of task A + 7mins)) as long as it is smaller than (endTime of
task A + 8mins).
Yes, it is pointless to investigate the solutions where task B starts
8 minutes after task A and the user doing no task that last minute.
The 8 minute is just a constraint that the task in between tasks A and
B cannot take longer than 7:59s.
I am thinking that maybe instead of using time itself as the planning
variable, we would use time just to determine the Hard and Soft scores.
So if Task B is scheduled after Task A + 8mins by the solver, then it
inflicts on the hard score. Similarly if Task B is scheduled before
Task A + 7 mins.
Does my reasoning make sense in any way?
Yes, but personally, I 'd design it differently (although I have no
proof that my way would be better), like this:
"Task B is scheduled after Task A + 8mins by the solver" => make this a
hard constraint
"Task B is scheduled before Task A + 7 mins" => make this a build-in
hard constraint (= not a constraint in the scoreDRL or ScoreCalculator,
but by design, see manual).
Each Task is assigned to a previousTaskOrPerson (and this variable is
chained). It does not know it's startingTime directly.
The scoreDRL or ScoreCalculator calculates the startingTime of a Task
dynamically, by applying this logic:
starting time of B = Math.max((endTime of previousTaskOrPerson of B),
(endTime of task A + 7mins))
Note: "Chained=true" guarantees that there are no cycles of Tasks and
that no Tasks exists with a previousTaskOrPerson == null.
Note: "(endTime of task A + 7mins)" is not hard coded in the score
function: you won't find "7" or "A" in there.
thanks,
Josef
On 24 July 2012 20:46, Geoffrey De Smet <ge0ffrey.s...@gmail.com
<mailto:ge0ffrey.s...@gmail.com>> wrote:
Op 23-07-12 16 <tel:23-07-12%2016>:26, Josef Bajada schreef:
Hi Geoffrey,
Well I want to leave 'space' between tasks in the situations
where there are hard constraints that require me to put this space.
This makes the chaining technique harder to model, but I wouldn't
write it off yet.
As a simple example:
Task A: Put pasta in boiling water (duration 40 seconds)
Task B: Take pasta out of boiling water (duration 50 seconds,
cannot start before 7 mins after Task A finishes, cannot start
after 8 mins after Task A finishes)
Does it make sense to wait longer than 7 mins after task A
(presuming no other task forces occupies the user at that time)?
Put differently: Can we say that the starting time of B =
Math.max((endTime of task before B), (endTime of task A + 7 minutes))?
If we can say that, it's pointless to investigate the solutions
where task B starts 8 minutes after task A and the user doing no
task that last minute.
If we can say that, then chaining can calculate the the starting
time of a task on the fly differently.
Task C: Chop vegetables (duration 2 minutes).
This will evidently leave some gaps. The ideal result from the
solver should be:
Task A: at time 0 (ends at 40s)
Task C: at time 41s (ends at 2:41)
Task B: at time 7:40
There is a gap between C and B which is OK.
If another Task is added to the story:
Task D: Prepare sauce (duration 7 minutes)
I would want the following result:
Task A: at time 0 (ends at 40s)
Task D: at time 41s (ends 7:41s)
Task B: at time 8:42s (ends 9:32s)
Task C: at time 9:33s (ends 11:33s)
Task C can actually take place before Task A too.
I still need to read and understand the chaining functionality
properly. Do you think it would allow me to achieve the above?
I don't know.
But using continuous variables in a search problem such as this
that smells discrete with discrete constraints (A must start
before B, ...), could blow up the search space unnecessarily.
If you want to look into using continuous variables: the support
for it is limited currently.
you can reuse the Drools Planner metaheuristic algorithms
(including termination, score, ...), but there's no decent generic
move factory support for continuous variables yet.
So you 'll have to write a custom MoveFactory that creates a
limited subset of moves.
Also, construction heuristics can't handle continuous variables
yet, so you 'll have to write a custom SolutionIntializer.
There are examples with a custom MoveFactory and a custom
SolutionIntializer where you can copy paste from, but none with
continuous variables at the moment.
thanks,
Josef
On 22 July 2012 20:05, Geoffrey De Smet <ge0ffrey.s...@gmail.com
<mailto:ge0ffrey.s...@gmail.com>> wrote:
Presuming that you don't want to leave space between tasks,
you can design your model differently by using the "chained"
functionality:
it will be far more efficient and the planning variable won't
be continuous.
Let's presume you're scheduling Tasks to Persons.
@PlanningEntity
class Task implements TaskOrPerson {
...
@PlanningVariable(chained = true)
@ValueRanges({
@ValueRange(type =
ValueRangeType.FROM_SOLUTION_PROPERTY, solutionProperty =
"taskList"),
@ValueRange(type =
ValueRangeType.FROM_SOLUTION_PROPERTY, solutionProperty =
"personList",
excludeUninitializedPlanningEntity = true)})
public TaskOrPerson getPreviousTaskOrPerson() {
return previousTaskOrPerson;
}
public int getDuration() {
return duration;
}
public int getStartingTime() {
int startingTime = 0;
TaskOrPerson taskOrPerson = getPreviousTaskOrPerson();
while (taskOrPerson instanceof Task) { // Every
chain is guarantee to end up with an anchor (= Person)
startingTime += ((Task)
taskOrPerson).getDuration();
taskOrPerson = ((Task)
taskOrPerson).getPreviousTaskOrPerson()
}
return startingTime;
}
}
class Person implements TaskOrPerson {
}
For a good example, take a look at the VehicleRouting example.
For more info about chaining, in the manual see section
4.3.4.2.6. Chained
http://docs.jboss.org/drools/release/5.4.0.Final/drools-planner-docs/html_single/index.html
Op 22-07-12 18 <tel:22-07-12%2018>:00, Josef Bajada schreef:
Hi,
I am new to Drools and Drools Planner, so apologies if I am
asking anything obvious.
My objective is to implement a simple (for now) planner
which schedules tasks according to 2 main criteria:
- Their duration (in seconds)
- Their dependencies on other tasks (e.g. Hard Constraint
that Task B has to start between 180 and 200 seconds after
Task A finishes).
Since there are gaps between dependent tasks as part of the
hard constraints other tasks can be fitted in between
dependent tasks.
So the Solver needs to find the optimal start time for each
task that satisfies the hard constraints, and in the
shortest total timeline possible to complete all tasks (soft
constraint).
The main problem I am finding is that this start time, which
is essentially the planning variable is a continuous variable.
Chapter 4 of the Drools documentation mentions very briefly
(Section 4.3.4.1) that planning variables can be
continuous, but there does not seem to be any more details
about how to achieve this.
Even if the planning variable was discrete (say bins of 5
second intervals), there is no upper bound as such.
How is it best to handle such planning variables in Drools
Planner?
thanks,
josef
_______________________________________________
rules-users mailing list
rules-users@lists.jboss.org <mailto:rules-users@lists.jboss.org>
https://lists.jboss.org/mailman/listinfo/rules-users
--
With kind regards,
Geoffrey De Smet
_______________________________________________
rules-users mailing list
rules-users@lists.jboss.org <mailto:rules-users@lists.jboss.org>
https://lists.jboss.org/mailman/listinfo/rules-users
_______________________________________________
rules-users mailing list
rules-users@lists.jboss.org <mailto:rules-users@lists.jboss.org>
https://lists.jboss.org/mailman/listinfo/rules-users
--
With kind regards,
Geoffrey De Smet
_______________________________________________
rules-users mailing list
rules-users@lists.jboss.org <mailto:rules-users@lists.jboss.org>
https://lists.jboss.org/mailman/listinfo/rules-users
_______________________________________________
rules-users mailing list
rules-users@lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
--
With kind regards,
Geoffrey De Smet
_______________________________________________
rules-users mailing list
rules-users@lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
