python – pickle与PuLP玩得不好

我正在使用Python 2.7并使用PuLP库来设置问题.一旦定义了变量,目标和约束,我就会挑选我的LpProblem对象以发送给其他地方的Solver.在解开我的问题时,我注意到所有变量都是重复的：

import pulp
import pickle

prob = pulp.LpProblem('test problem', pulp.LpMaximize)
x = pulp.LpVariable('x', 0, 10)
y = pulp.LpVariable('y', 3, 6)
prob += x + y
prob += x <= 5

print prob
print pickle.loads(pickle.dumps(prob))

第一个打印声明输出：

>>> print prob
test problem:
MAXIMIZE
1*x + 1*y + 0
SUBJECT TO
_C1: x <= 5

VARIABLES
x <= 10 Continuous
3 <= y <= 6 Continuous

而第二次打印：

>>> print pickle.loads(pickle.dumps(prob))
test problem:
MAXIMIZE
1*x + 1*y + 0
SUBJECT TO
_C1: x <= 5

VARIABLES
x <= 10 Continuous
x <= 10 Continuous
3 <= y <= 6 Continuous
3 <= y <= 6 Continuous

如您所见,目标和约束都很好,但所有变量都是重复的.导致此行为的原因是什么,以及如何防止这种情况发生？

解决方法:

所以我还没弄清楚为什么会发生这种情况,但我确实有办法解决陷入同样情况的人：

def UnpicklePulpProblem(pickled_problem):
    wrong_result = pickle.loads(pickled_problem)
    result = pulp.LpProblem(wrong_result.name, wrong_result.sense)
    result += wrong_result.objective
    for i in wrong_result.constraints: result += wrong_result.constraints[i], i
    return result

以这种方式添加目标和约束可确保变量仅在问题中定义一次,因为您基本上是从头开始以这种方式重建问题.

标签：python,pickle,linear-programming,pulp
来源： https://codeday.me/bug/20190708/1405431.html