First draft for n tasks in time intervals

[tpaviot]

@dreinon I started implementing the constraint for n tasks in time intervals. The new constraint name is ScheduleNTasksInTimeIntervals, you can use it with:

cstrt = ps.ScheduleNTasksInTimeIntervals([task_1, task_2, task_3], nb_tasks_to_schedule= 2,
                                          list_of_time_intervals = [[1, 10], [13, 20]])
pb.add_constraint(cstrt)

This means the solver will schedule exactly 2 tasks among the list [task_1, task_2, task_3] in the slots that are given in the list list_of_time_intervals. So far, it does not work as expected: tasks that partially overlap the time intervals are scheduled whereas they should not, I guess it comes from a mistake in the z3 assertion (the And statement does not prevent such tasks to be scheduled).

[codecov-commenter]

Codecov Report

Merging #20 (b56f01f) into master (dc505a1) will increase coverage by 0.01%. The diff coverage is 98.00%.

@@            Coverage Diff             @@
##           master      #20      +/-   ##
==========================================
+ Coverage   97.82%   97.83%   +0.01%     
==========================================
  Files          20       21       +1     
  Lines        2209     2358     +149     
==========================================
+ Hits         2161     2307     +146     
- Misses         48       51       +3     

Impacted Files	Coverage Δ
processscheduler/task_constraint.py	95.54% <92.30%> (-0.68%)	:arrow_down:
test/test_schedule_n_task_in_time_interval.py	99.19% <99.19%> (ø)

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[dreinon]

@dreinon I started implementing the constraint for n tasks in time intervals. The new constraint name is ScheduleNTasksInTimeIntervals, you can use it with:

cstrt = ps.ScheduleNTasksInTimeIntervals([task_1, task_2, task_3], nb_tasks_to_schedule= 2,
                                          list_of_time_intervals = [[1, 10], [13, 20]])
pb.add_constraint(cstrt)

This means the solver will schedule exactly 2 tasks among the list [task_1, task_2, task_3] in the slots that are given in the list list_of_time_intervals. So far, it does not work as expected: tasks that partially overlap the time intervals are scheduled whereas they should not, I guess it comes from a mistake in the z3 assertion (the And statement does not prevent such tasks to be scheduled).

Thanks Thomas, I'm glad this project is becoming bigger and better :)

I didn't understand well the list of time intervals.

So if I say that

ps.ScheduleNTasksInTimeIntervals([task_1, task_2, task_3], nb_tasks_to_schedule=2, list_of_time_intervals = [[1, 10], [13, 20]])

The functionality we are approaching is that a maximum of 2 tasks will be scheduled between all those time intervals, or that a maximum of 2 tasks will be scheduled in each separate interval?

I mean, in the first case I described, an option would be 1 task between [1,10] and another 1 between [13,20], but it wouldn't be 1 task between [1,10] and 2 between [13,20], whereas in the second option, 1 task between [1,10] and 2 between [13,20] would be an option.

Thanks.

[tpaviot]

As it is currently implemented, in the previous example, exactly 2 tasks will be scheduled over both intervals. If you want a maximum of 2 tasks, then you have to set the kind parameter:

cstrt = ps.ScheduleNTasksInTimeIntervals([task_1, task_2, task_3],
                                                 nb_tasks_to_schedule= 2,
                                                 list_of_time_intervals = [[1, 10], [13, 20]],
                                                 kind='atmost')

If you want that a maximum of 2 tasks are scheduled on the first interval, and a maximum on 2 tasks are scheduled on the second interval, then create 2 constraints:

cstrt = ps.ScheduleNTasksInTimeIntervals([task_1, task_2, task_3],
                                                 nb_tasks_to_schedule= 2,
                                                 list_of_time_intervals = [[1, 10]],
                                                 kind='atmost')
cstrt = ps.ScheduleNTasksInTimeIntervals([task_1, task_2, task_3],
                                                 nb_tasks_to_schedule= 2,
                                                 list_of_time_intervals = [[13, 20]],
                                                 kind='atmost')

[dreinon]

Got it! Nice approach!!

[lgtm-com[bot]]

This pull request introduces 2 alerts when merging 3366009f9a42205ba9b0cba7cbf8baa5ce765cf3 into f8f9c362e81567ae271064c5910c61df9f9279f1 - view on LGTM.com

new alerts:

• 1 for Unused local variable
• 1 for Unused import

[tpaviot]

The current dev branch should work now, but it has to be tested.

[dreinon]

Just reviewed tests, new constraint code and new to-do file. Way to go!!

[tpaviot]

ok, I merge the code into the master branch, we'll see if other fixes are required after a deeper testing.