我正在使用 Python 2.7 并使用 PuLP 库设置问题。一旦定义了变量、目标和约束,我就会挑选我的 LpProblem 对象以发送到别处的求解器。解决我的问题后,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))
第一个打印语句输出:
>>> print prob
test problem:
MAXIMIZE
1*x + 1*y + 0
SUBJECT TO
_C1: x <= 5
VARIABLES
x <= 10 Continuous
3 <= y <= 6 Continuous
第二次打印时:
>>> 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。是什么导致了这种行为,我该如何防止这种情况发生?
最佳答案
所以我还没有弄清楚为什么会发生这种情况,但对于陷入相同情况的任何人,我确实有办法解决它:
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,因为您基本上是以这种方式从头开始重建问题。
关于python - pickle 不能与 PuLP 一起玩,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/22849208/