指定在OR-Tools中打印的解决方案

问题描述

例如，当我在轮班计划中遇到以下问题时，如何使用SolveWithSolutionCallback方法指定要打印的解决方案？

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

比方说，我想看看解决方案13和14产生了什么，有什么办法吗？

解决方法

您可以将解决方案存储在回调的列表中，或将其记录到文件中，等等：

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,"y")
    z = model.NewIntVar(0,"z")

    model.Add(x != y)

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