使用JuMP时如何转换变量的类型 [英] How to convert type of a variable when using JuMP

问题描述

我正在使用Julia/JuMP来实现算法.在一部分中，我定义了一个带有连续变量的模型并求解线性模型.我进行了一些其他计算，在这些计算的基础上，我向模型添加了一些约束，然后我想使用整数变量来解决相同的问题.我不能使用convert()函数，因为它没有变量.

I am using Julia/JuMP to implement an algorithm. In one part, I define a model with continues variables and solve the linear model. I do some other calculations based on which I add a couple constraints to the model, and then I want to solve the same problem but with integer variables. I could not use convert() function as it does not take variables.

我试图再次将变量定义为整数，但是模型似乎没有考虑它！我在这里提供了示例代码:

I tried to define the variable again as integer, but the model did not seem to consider it! I provide a sample code here:

m = Model()
@defVar(m, 0 <= x <= 5)
@setObjective(m, Max, x)
@addConstraint(m, con, x <= 3.1)
solve(m) 
println(getValue(x))
@defVar(m, 0 <= x <= 1, Bin)
solve(m) 
println(getValue(x))

请您帮我完成一次转换吗?

Would you please help me do this conversion?

推荐答案

问题是第二个@variable(m, 0 <= x <= 1, Bin)实际上在模型中创建了一个新变量，但在Julia中具有相同的名称.

The problem is that the second @variable(m, 0 <= x <= 1, Bin) actually creates a new variable in the model, but with the same name in Julia.

要将变量从连续变量更改为二进制变量，可以执行

To change a variable from a continuous to a binary, you can do

setcategory(x, :Bin)

在再次调用Solve之前更改变量范围和类.

to change the variable bounds and class before calling solve again.

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