Pyomo:在使用python脚本的时候，有没有什么快速的方法可以在解决ILP后显示Objective值? [英] Pyomo: When using python script, are there any quick ways to show the Objective value after solving the ILP?

问题描述

我之前完成了一个 ILP，它工作正常.

I finished an ILP before and it works properly.

opt = SolverFactory('glpk')
model = AbstractModel()
model.obj = Objective(...)

# variables, constraints ...

instance = model.create_instance()
results = opt.solve(instance)

因为我想获得每个变量的值，而且还想得到目标函数，所以我尝试通过与我对变量所做的类似的方式访问目标函数，但我只能得到一个表达式.

since I want to get the value of each variable but also the objective function solved, I try to access the Objective function by the way similar as what I did to the variable but all I can get is an expression.

我使用以下代码:

print(instance.obj.value)

但只得到这样的警告:

WARNING: DEPRECATED: The .value property getter on SimpleObjective is deprecated. Use the .expr property getter instead

当我将代码更改为

print(instance.obj.expr)

我得到的只是一个表达.所以我想知道除了获取所有需要的变量并再次自己重新计算之外，还有什么方法可以获得目标函数的值吗?

All I get is an expression. So I wanna know is there any way to get the value of the objective function other than getting all the variables needed and re-calculating by myself again?

推荐答案

获取目标函数值的最好方法是使用Pyomo提供的value函数

The best way to get the value of the objective function is to use the value function provided by Pyomo

print(value(instance.obj))

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