Newbie - Optimal Shift Pattern

[SteveHaine]

OK so I'm new to or-tools an I'm interested if it can find an optimal shift pattern for a set of work. So I have various work to be done which start at different time and have different lengths, I need to find the most optimal (smallest number of employees) shift pattern to fulfil this demand, but as always their are constraints.

Having done a bit of reading I guess this problem lends itself to CP-SAT. Ive seen the nurse scheduling problem but we need to be more dynamic i.e. some shifts can be 5hs and some can be 10hrs but at the end of the pattern each shift rotation must have done the same amount of work.

Any pointers would be gratefully received.

[Mizux]

Did you take a look at the [flexible] jobshop problem instead ?
and replace "machine" by "worker"...

src: https://github.com/google/or-tools/blob/stable/examples/python/flexible_job_shop_sat.py

[SteveHaine]

Thanks @Mizux, That Looks much closer to what's required, am I correct I saying the main area I would need to amend would be:

or-tools/examples/python/flexible_job_shop_sat.py

Lines 148 to 152 in b77bd3a

	# Create machines constraints.
	for machine_id in all_machines:
	intervals = intervals_per_resources[machine_id]
	if len(intervals) > 1:
	model.AddNoOverlap(intervals)

To add employee working time constraints?

Also how would it give me the minimum number of Machines (workers) required?

Steve

[Mizux]

The objective here is to finish ASAP i.e. minimize makespan, so it won't minimize the number of workers.

or-tools/examples/python/flexible_job_shop_sat.py

Lines 154 to 157 in b77bd3a

	# Makespan objective
	makespan = model.NewIntVar(0, horizon, 'makespan')
	model.AddMaxEquality(makespan, job_ends)
	model.Minimize(makespan)

You could try instead to create a boolean for each machine which will be true if at least one task is performed on it, then as objective minimize the sum of the boolean values...

[lperron]

maximize the sum of boolean values. Laurent Perron | Operations Research | [email protected] | (33) 1 42 68 53 00 Le ven. 8 janv. 2021 à 09:42, Mizux <[email protected]> a écrit :

…

The objective here is to finish ASAP i.e. minimize makespan, so it won't minimize the number of workers. https://github.com/google/or-tools/blob/b77bd3ac69b7f3bb02f55b7bab6cbb4bab3917f2/examples/python/flexible_job_shop_sat.py#L154-L157 You could try instead to create a boolean for each machine which will be true if at least one task is performed on it, then as objective minimize the sum of the boolean values... — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#2324 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACUPL3IUGPNDEXANXSHSXKTSY3AQ5ANCNFSM4VZOB2YQ> .