I'm modifying the code from here and I want to be able to add different length of shifts for certain day.(For example, I want Friday/Day 4 to have only 2 shifts). My code keeps ending with error code. I believe it is due to some internal problem with the constraints I've set.
I saw a couple of post on StackOverflow on similar programs but can't find one that addresses my specific problem.
from ortools.sat.python import cp_model
class employeePartialSolutionPrinter(cp_model.CpSolverSolutionCallback):
"""Print intermediate solutions."""
def __init__(self, shifts, num_employee, num_days, num_shifts, sols):
cp_model.CpSolverSolutionCallback.__init__(self)
self._shifts = shifts
self._num_employee = num_employee
self._num_days = num_days
self._num_shifts = num_shifts
self._solutions = set(sols)
self._solution_count = 0
def on_solution_callback(self):
self._solution_count += 1
if self._solution_count in self._solutions:
print('Solution %i' % self._solution_count)
for d in range(self._num_days):
print('Day %i' % d)
for n in range(self._num_employee):
is_working = False
for s in range(self._num_shifts):
if self.Value(self._shifts[(n, d, s)]):
is_working = True
print(' Employee %i works shift %i' % (n, s))
if not is_working:
print(' Employee {} does not work'.format(n))
def solution_count(self):
return self._solution_count
model = cp_model.CpModel()
solver = cp_model.CpSolver()
num_employee = 5
num_shifts = 5
num_days = 5
all_employee = range(num_employee)
all_shifts = range(num_shifts)
all_days = range(num_days)
# Normal Hours
# Monday-Thursday Shift 0-4
# Friday Shift 0-1
friday_deduct = 3
shifts = {}
for n in all_employee:
for d in all_days:
if d == 4:
for s in range(num_shifts-friday_deduct):
shifts[(n, d, s)] = model.NewBoolVar('shift_n%id%is%i' % (n, d, s))
else:
for s in all_shifts:
shifts[(n,d,s)] = model.NewBoolVar('shift_n%id%is%i' % (n,d,s))
"""
Constraints (Normal Time)
"""
# Each Shift is assigned to a single person per day
# Shift 2 need to be assigned to 3 person
# Shift 1 and 3 need to be assigned to 2 person
for d in all_days:
if d == 4:
for s in range(num_shifts-friday_deduct):
if s == 1:
model.Add(sum(shifts[(n, d, s)] for n in all_employee) == 2)
else:
model.Add(sum(shifts[(n, d, s)] for n in all_employee) == 1)
else:
for s in all_shifts:
if s == 2 :
model.Add(sum(shifts[(n,d,s)] for n in all_employee) == 3)
elif s == 3 or s == 1:
model.Add(sum(shifts[(n, d, s)] for n in all_employee) == 2)
else:
model.Add(sum(shifts[(n,d,s)] for n in all_employee) == 1)
#Each nurse works at most 10 shift per week, at least 4 shift per week
for n in range(num_employee):
week = []
for d in all_days:
if d == 4:
for s in range(num_shifts-friday_deduct):
week.append(shifts[(n,d,s)])
# week.append(sum(shifts[(n, d, s)] for s in range(num_shifts-friday_deduct)))
else:
for s in all_shifts:
week.append(shifts[(n,d,s)])
# week.append(sum(shifts[(n,d,s)] for s in all_shifts))
model.Add(sum(week) >= 4)
model.Add(sum(week) <=10)
solver.parameters.linearization_level = 0
a_few_solutions = range(5)
solution_printer = employeePartialSolutionPrinter(shifts, num_employee,
num_days, num_shifts, a_few_solutions)
solver.SearchForAllSolutions(model, solution_printer)
Here is the printout from Pycharm IDE. When I run it from a command-line, the window "Python has stopped working" came up.
Solution 1
Day 0
Employee 0 does not work
Employee 1 does not work
Employee 2 works shift 2
Employee 3 works shift 1
Employee 3 works shift 2
Employee 3 works shift 3
Employee 3 works shift 4
Employee 4 works shift 0
Employee 4 works shift 1
Employee 4 works shift 2
Employee 4 works shift 3
Day 1
Employee 0 works shift 2
Employee 0 works shift 3
Employee 0 works shift 4
Employee 1 works shift 2
Employee 2 works shift 1
Employee 2 works shift 2
Employee 2 works shift 3
Employee 3 works shift 0
Employee 3 works shift 1
Employee 4 does not work
Day 2
Employee 0 works shift 2
Employee 0 works shift 3
Employee 0 works shift 4
Employee 1 works shift 0
Employee 1 works shift 1
Employee 1 works shift 2
Employee 1 works shift 3
Employee 2 works shift 1
Employee 2 works shift 2
Employee 3 does not work
Employee 4 does not work
Day 3
Employee 0 works shift 2
Employee 0 works shift 3
Employee 0 works shift 4
Employee 1 works shift 1
Employee 1 works shift 2
Employee 1 works shift 3
Employee 2 works shift 0
Employee 2 works shift 1
Employee 2 works shift 2
Employee 3 does not work
Employee 4 does not work
Day 4
Process finished with exit code -1073740791 (0xC0000409)
You have a key error on your callback (day 4 only has 2 shifts):
for s in range(self._num_shifts):
if self.Value(self._shifts[(n, d, s)]):
a simple check will do:
if (n, d, s) in self._shifts and self.Value(
self._shifts[(n, d, s)]
):
but you should definitely take a look at the other example that Laurent suggested. https://github.com/google/or-tools/blob/master/examples/python/shift_scheduling_sat.py