def _schedule_all_events(events, slots, X, summation_type=None):
shape = Shape(len(events), len(slots))
summation = lpu.summation_functions[summation_type]
label = 'Event either not scheduled or scheduled multiple times'
for event in range(shape.events):
yield Constraint(
f'{label} - event: {event}',
summation(X[event, slot] for slot in range(shape.slots)) == 1)
def _max_one_event_per_slot(events, slots, X, summation_type=None):
shape = Shape(len(events), len(slots))
summation = lpu.summation_functions[summation_type]
label = 'Slot with multiple events scheduled'
for slot in range(shape.slots):
yield Constraint(
f'{label} - slot: {slot}',
summation(X[(event, slot)] for event in range(shape.events)) <= 1)
def solution(events, slots, objective_function=None, solver=None, **kwargs):
"""Compute a schedule in solution form
Parameters
----------
events : list or tuple
of :py:class:`resources.Event` instances
slots : list or tuple
of :py:class:`resources.Slot` instances
solver : pulp.solver
a pulp solver
objective_function: callable
from lp_problem.objective_functions
kwargs : keyword arguments
arguments for the objective function
Returns
-------
list
A list of tuples giving the event and slot index (for the given
events and slots lists) for all scheduled items.
Example
-------
For a solution where
* event 0 is scheduled in slot 1
* event 1 is scheduled in slot 4
* event 2 is scheduled in slot 5
the resulting list would be::
[(0, 1), (1, 4), (2, 5)]
"""
shape = Shape(len(events), len(slots))
problem = pulp.LpProblem()
X = lp.utils.variables(shape)
beta = pulp.LpVariable("upper_bound")
for constraint in lp.constraints.all_constraints(events, slots, X, beta,
'lpsum'):
problem += constraint.condition
if objective_function is not None:
problem += objective_function(events=events,
slots=slots,
X=X,
beta=beta,
**kwargs)
status = problem.solve(solver=solver)
if status == 1:
return [item for item, variable in X.items() if variable.value() > 0]
else:
raise ValueError('No valid solution found')
def shape(events, slots):
return Shape(len(events), len(slots))