指定在 OR-Tools 中打印的解决方案

Question

当我得到下面的解决方案时，例如在轮班安排坐问题中，我如何指定我想用 SolveWithSolutionCallback 方法打印的解决方案？

Solution 13, time = 37.58 s, objective = 82
Solution 14, time = 37.71 s, objective = 81
Solution 15, time = 37.87 s, objective = 80
Solution 16, time = 37.96 s, objective = 76

假设我想看看解决方案 13 和 14 产生了什么，有什么办法吗？

Answer 1

您可以将解决方案存储在回调的列表中或将它们记录到文件等：

from ortools.sat.python import cp_model


class Callback(cp_model.CpSolverSolutionCallback):

    def __init__(self, variables):
        cp_model.CpSolverSolutionCallback.__init__(self)
        self.variables = variables
        self.solutions = []

    def on_solution_callback(self):
        self.solutions.append([self.Value(v) for v in self.variables])


if __name__ == "__main__":
    model = cp_model.CpModel()

    num_vals = 3
    x = model.NewIntVar(0, num_vals - 1, "x")
    y = model.NewIntVar(0, num_vals - 1, "y")
    z = model.NewIntVar(0, num_vals - 1, "z")

    model.Add(x != y)

    solver = cp_model.CpSolver()
    callback = Callback([x, y, z])
    solver.SearchForAllSolutions(model, callback)
    print(callback.solutions)