Resource Time Windows Spanning Multiple Periods for Job Shop Scheduling using Ortools Sat Python cp_models

[Bruceholt2]

In the ProcessingScheduler package in Python PYPI, there are four resource constraints that are available. These four are:

• ResourcePeriodicallyUnavailable,
• ResourcePeriodicallyInterrupted,
• ResourceInterrupted and
• Resource Unavailable.

Is there anything (examples, documentation) like these available for OR-Tools Sat Python cp_models?

[lperron]

I do not understand the differences between all 4. What does interrupted entail ?

[Mizux]

ref: https://processscheduler.github.io/

Seems to use internally the z3 solver: https://github.com/tpaviot/ProcessScheduler/blob/83f0c145f4117129779da3366725a54cef48279e/poetry.lock#L188-L190

[Mizux]

@Bruceholt2 did you take a look at https://github.com/tpaviot/ProcessScheduler/blob/83f0c145f4117129779da3366725a54cef48279e/processscheduler/resource_constraint.py to see how ProcessScheduler model it in z3 so you can try to reproduce it with CP-Sat ?
Please note, cp-sat is a generic constraint solver (like z3), then you need to build a Process Scheduler/Job Shop Scheduling on top of it, we only provide some jobshop examples just as a basic starting point...

[Bruceholt2]

Thanks for you response. However, I am new to Python and do not have the programming experience to be able to duplicate code for cp-sat. I looked at the option to create code for cp-sat but found it overwhelming. Thanks again.

[Bruceholt2]

From: Laurent Perron I do not understand the differences between all 4. What does interrupted entail ?

I’ll try to explain. I use the *Periodic Interrupted* to define intervals on the time line where *work* cannot be performed. As an example, if a *task* has a start time planned to start at hour 8 on the timeline and the task is 4 hours long. On a contiguous time line, the *task* would be performed from hour 8 to hour 12. However, if I define a *break period* from 10 to 11, then the task would need to extend it’s duration by 1 hour in order to still perform the 4 hour task. The duration would increase by 1 hour so now the task will be performed from 8 to 10 ( 2 hours), a break for 1 hour, and resume task work from 11 to 13 (2 hours). The duration must change from 4 to 5 to account for the 1 hour of time unavailable during the break. The ‘periodic’ method allows for the establishment of multiple intervals of no work and also allows the use of periods which can extend the unable periods by the length of the period. Someone may be able to better explain but hope this helps.