我正在尝试使用熟悉 google or-tools。我尝试了员工调度 python 示例的简化版本。
from __future__ import print_function
import sys
from ortools.constraint_solver import pywrapcp
def main():
# Creates the solver.
solver = pywrapcp.Solver("employee_scheduling")
num_nurses = 3
num_shifts = 3
num_days = 1
# [START]
# Create shift variables.
shifts = {}
for j in range(num_nurses):
for i in range(num_days):
shifts[(j, i)] = solver.IntVar(
0, num_shifts - 1, "shifts(%i,%i)" % (j, i))
shifts_flat = [shifts[(j, i)] for j in range(num_nurses)
for i in range(num_days)]
# Create nurse variables.
nurses = {}
for j in range(num_shifts):
for i in range(num_days):
nurses[(j, i)] = solver.IntVar(
0, num_nurses - 1, "shift%d day%d" % (j, i))
# Set relationships between shifts and nurses.
for day in range(num_days):
nurses_for_day = [nurses[(j, day)] for j in range(num_shifts)]
for j in range(num_nurses):
s = shifts[(j, day)]
solver.Add(s.IndexOf(nurses_for_day) == j)
# Create the decision builder.
db = solver.Phase(shifts_flat, solver.CHOOSE_FIRST_UNBOUND,
solver.ASSIGN_MIN_VALUE)
# Create the solution collector.
solution = solver.Assignment()
solution.Add(shifts_flat)
collector = solver.AllSolutionCollector(solution)
solver.Solve(db, [collector])
print("Solutions found:", collector.SolutionCount())
print("Time:", solver.WallTime(), "ms")
print()
if __name__ == "__main__":
main()
如您所见，我保留的唯一限制是轮班和护士之间的关系。当 num_nurses = 3、num_shifts = 3 和 num_days = 1 时，求解器能够找到 6 个解。但是，如果我将 num_shifts 更改为 2，求解器将返回 0 个解决方案。这不应该也有3个解决方案（分配一名护士，不分配其他两名）？