def solve_intermediate_objective(
model: cp_model.CpModel,
solver: cp_model.CpSolver,
objective,
hint=True,
objective_type='min',
callback: Optional[cp_model.CpSolverSolutionCallback] = None,
alias=None,
max_time=None,
logger=logging):
if max_time:
solver.parameters.max_time_in_seconds = max_time
if objective_type.lower().startswith('min'):
model.Minimize(objective)
objective_type = 'min'
elif objective_type.lower().startswith('max'):
model.Maximize(objective)
objective_type = 'max'
else:
raise Exception(f'Can not "{objective_type}" objective')
t0 = dt.datetime.now()
if callback:
status = solver.SolveWithSolutionCallback(model, callback)
else:
status = solver.Solve(model)
duration = (dt.datetime.now() - t0).total_seconds()
if status == cp_model.INFEASIBLE:
logger.warning(f'INFEASIBLE solving {alias or objective}')
return None, status
elif status == cp_model.UNKNOWN:
logger.warning(f'Time limit reached {alias or objective}')
return None, status
result = round(solver.ObjectiveValue())
if hint:
hint_solution(model, solver)
if not isinstance(objective, int):
if status == cp_model.OPTIMAL:
logger.debug(
f'{alias or objective} == {result}, Seconds: {duration:.2f}')
model.Add(objective == result)
elif objective_type == 'min':
logger.debug(
f'{alias or objective} <= {result}, Seconds: {duration:.2f}')
model.Add(objective <= result)
elif objective_type == 'max':
logger.debug(
f'{alias or objective} >= {result}, Seconds: {duration:.2f}')
model.Add(objective >= result)
return result, status
def compute_optimal_bench_map(
schedule: Schedule,
all_employees: Dict[int, Employee],
all_shifts: Dict[int, Shift],
all_labs: Dict[str, Lab],
all_benches: Dict[str, Bench],
constraints: Constraints,
) -> Schedule:
# Make sure employees have home_bench information
for employee in all_employees:
assert all_employees[employee].home_bench is not None
model = CpModel()
bench_placement = {}
for shift in schedule.shift_schedule:
for employee in schedule.shift_schedule[shift]:
for bench in all_benches:
bench_placement[(
shift, employee.index, bench)] = model.NewBoolVar(
f"bench_s{shift}e{employee.index}b{bench}")
# 2 employees cannot have same bench
for shift in schedule.shift_schedule:
for bench in all_benches:
model.Add(
sum(bench_placement[(shift, employee.index, bench)]
for employee in schedule.shift_schedule[shift]) <= 1)
# All employees scheduled must have a bench for each shift
# Other employees must not have a bench
for shift in schedule.shift_schedule:
for employee in schedule.shift_schedule[shift]:
model.Add(
sum(bench_placement[(shift, employee.index, bench)]
for bench in all_benches) == 1)
# Make sure appropriate benches are utilized during appropriate shift
for shift in schedule.shift_schedule:
for bench in all_benches:
if (all_shifts[shift].label
== "FULL") and (all_benches[bench].active_shift == "AM"):
# This works because we want FULL shifts to use AM benches
# If proper condition, no constraint will be added
# If anything else, it will be added
# For example, FULL + PM will have constraint == 0
pass # important
elif (all_shifts[shift].label != all_benches[bench].active_shift):
model.Add(
sum(bench_placement[(shift, employee.index, bench)]
for employee in schedule.shift_schedule[shift]) == 0)
# Create objective
# Minimize distance from home bench to placed bench
model.Minimize(
sum(((
employee.home_bench.location.x # type: ignore
- all_benches[bench].location.x)**2 + (
employee.home_bench.location.y # type: ignore
- all_benches[bench].location.y)**2 + (
constraints.raw_lab_separation.loc[ # type: ignore
employee.home_bench.lab.name, # type: ignore
all_benches[bench].lab.name, ])) *
bench_placement[(shift, employee.index, bench)]
for shift in schedule.shift_schedule
for employee in schedule.shift_schedule[shift]
for bench in all_benches))
st.write("Running Location Optimization...")
solver = CpSolver()
solver.parameters.max_time_in_seconds = 60
solver.Solve(model)
st.write("Finished Location Optimization!")
shift_bench_schedule: Dict[int, Dict[int, Bench]] = {
} # {Shift.id: {Employee.id: Bench}}
shift_bench_schedule = {
shift: {
employee.index: all_benches[bench]
for employee in schedule.shift_schedule[shift]
for bench in all_benches
if solver.Value(bench_placement[(shift, employee.index, bench)])
}
for shift in all_shifts
}
employee_bench_schedule: Dict[int, Dict[int, Bench]] = {
} # {Employee.id: {Shift.id: Bench}}
for shift in shift_bench_schedule:
for employee in shift_bench_schedule[shift]:
employee_bench_schedule[employee] = {}
for shift in shift_bench_schedule:
for employee in shift_bench_schedule[shift]:
employee_bench_schedule[employee][shift] = shift_bench_schedule[
shift][employee]
employee_bench_distances: Dict[int, float] = {
} # {Employee.id: average distance}
for employee in employee_bench_schedule:
employee_bench_distances[employee] = statistics.mean([
((employee_bench_schedule[employee][shift].location.x -
all_employees[employee].home_bench.location.x)**2 +
(employee_bench_schedule[employee][shift].location.y -
all_employees[employee].home_bench.location.y)**2)**0.5
for shift in employee_bench_schedule[employee]
])
schedule.shift_bench_schedule = shift_bench_schedule
schedule.employee_bench_schedule = employee_bench_schedule
schedule.bench_objective_score = solver.ObjectiveValue()
schedule.bench_optimization_average_distance = employee_bench_distances
return schedule
def compute_optimal_schedule(
all_employees: Dict[int, Employee],
all_shifts: Dict[int, Shift],
all_days: Dict[str, Day],
schedule_parameters: ConstraintParameters,
) -> Schedule:
model = CpModel()
shifts = {}
for employee in all_employees:
for shift in all_shifts:
shifts[(employee,
shift)] = model.NewBoolVar(f"shift_e{employee}s{shift}")
# Each shift has max number of people
# Up to input to calculate AM + FULL and PM + FULL true constraints
for shift in all_shifts:
model.Add(
sum(shifts[(employee, shift)] for employee in all_employees) <=
all_shifts[shift].max_capacity)
# Each person has max slots
for employee in all_employees:
model.Add(
sum(shifts[(employee,
shift)] if all_shifts[shift].label != "FULL" else 2 *
shifts[(employee, shift)]
for shift in all_shifts) <= all_employees[employee].max_slots)
# A person can only have one of AM, PM, or FULL per day
for employee in all_employees:
for day in all_days:
model.Add(
sum(shifts[(employee, shift)] for shift in all_shifts
if all_shifts[shift].day == day) <= 1)
# A person might not be able to work all possible shifts
for employee in all_employees:
for shift in all_shifts:
if all_employees[employee].preferences[shift] <= -100:
model.Add(sum([shifts[(employee, shift)]]) < 1)
# Workaround for minimizing variance of scores
# Instead, minimize difference between max score and min score
# From: https://stackoverflow.com/a/53363585
employee_scores = {}
for employee in all_employees:
employee_scores[employee] = model.NewIntVar(
-100, 100, f"employee_score_{employee}")
model.Add(employee_scores[employee] == sum(
all_employees[employee].preferences[shift] *
shifts[(employee,
shift)] if all_shifts[shift].label != "FULL" else 2 *
all_employees[employee].preferences[shift] *
shifts[(employee, shift)] for shift in all_shifts))
min_employee_score = model.NewIntVar(-100, 100, "min_employee_score")
max_employee_score = model.NewIntVar(-100, 100, "max_employee_score")
model.AddMinEquality(min_employee_score,
[employee_scores[e] for e in all_employees])
model.AddMaxEquality(max_employee_score,
[employee_scores[e] for e in all_employees])
# Max Unfairness constraint
if schedule_parameters.max_unfairness >= 0:
model.Add(max_employee_score -
min_employee_score <= schedule_parameters.max_unfairness)
# Create objective
# Maximize points from requests
# Maximize number of shifts filled
# Minimize variance of scores per employee
weights: Dict[str, int] = {
"preferences":
int(10 * (1 / (1 + schedule_parameters.fill_schedule_weight +
schedule_parameters.fairness_weight))),
"fill_schedule":
int(10 * (schedule_parameters.fill_schedule_weight /
(1 + schedule_parameters.fill_schedule_weight +
schedule_parameters.fairness_weight))),
"fairness":
int(10 * (schedule_parameters.fairness_weight /
(1 + schedule_parameters.fill_schedule_weight +
schedule_parameters.fairness_weight))),
}
model.Maximize(weights["preferences"] * sum(
all_employees[employee].preferences[shift] * shifts[
(employee, shift)] if all_shifts[shift].label != "FULL" else 2 *
all_employees[employee].preferences[shift] * shifts[(employee, shift)]
for employee in all_employees for shift in all_shifts) +
weights["fill_schedule"] * sum(shifts[(employee, shift)]
for employee in all_employees
for shift in all_shifts) -
weights["fairness"] *
(max_employee_score - min_employee_score))
st.write("Constraints set up. Running Optimization...")
solver = CpSolver()
solver.parameters.max_time_in_seconds = 60
solver.Solve(model)
st.write("Finished Schedule Optimization!")
# Prepare results
shifts_per_employee: Dict[int, int] = {
employee: sum(
solver.Value(shifts[(
employee,
shift)]) if all_shifts[shift].label != "FULL" else 2 *
solver.Value(shifts[(employee, shift)]) for shift in all_shifts)
for employee in all_employees
}
score_per_employee: Dict[int, int] = {
employee:
sum(all_employees[employee].preferences[shift] * solver.Value(shifts[
(employee, shift)]) if all_shifts[shift].label != "FULL" else 2 *
all_employees[employee].preferences[shift] *
solver.Value(shifts[(employee, shift)]) for shift in all_shifts)
for employee in all_employees
}
score_variance: float = statistics.variance(score_per_employee.values())
total_possible_shifts: int = sum(
all_shifts[shift].
max_capacity if all_shifts[shift].label != "FULL" else 2 *
all_shifts[shift].max_capacity for shift in all_shifts)
employee_schedule: Dict[int, List[Shift]] = {
employee: [
all_shifts[shift] for shift in all_shifts
if solver.Value(shifts[(employee, shift)])
]
for employee in all_employees
}
shift_schedule: Dict[int, List[Employee]] = {
shift: [
all_employees[employee] for employee in all_employees
if solver.Value(shifts[(employee, shift)])
]
for shift in all_shifts
}
schedule: Schedule = Schedule(
objective_score=solver.ObjectiveValue(),
time_to_solve=solver.WallTime(),
number_of_shifts_per_employee=shifts_per_employee,
score_per_employee=score_per_employee,
score_variance=score_variance,
min_employee_score=solver.Value(min_employee_score),
max_employee_score=solver.Value(max_employee_score),
total_possible_shifts=total_possible_shifts,
total_shifts_filled=sum(shifts_per_employee.values()),
employee_schedule=employee_schedule,
shift_schedule=shift_schedule,
)
return schedule