Julia/JuMP 中带有 2 个迭代器的 For 循环

Question

我需要为 JuMP/Julia 实现以下伪代码：

forall{i in M, j in Ni[i]}:  x[i] <= y[j];

我想像：

for i in M and j in Ni[i]
    @constraint(model, x[i] <= y[j])
end

如何在 for 循环中正确实现 2 个迭代器？

Answer 1

我不知道您是否想要一个具有两个值的迭代，或者迭代器的笛卡尔积，但这里是两者的示例：

julia> M = 1:3; N = 4:6;

julia> for (m, n) in zip(M, N) # single iterator over both M and N
           @show m, n
       end
(m, n) = (1, 4)
(m, n) = (2, 5)
(m, n) = (3, 6)

julia> for m in M, n in N # Cartesian product
           @show m, n
       end
(m, n) = (1, 4)
(m, n) = (1, 5)
(m, n) = (1, 6)
(m, n) = (2, 4)
(m, n) = (2, 5)
(m, n) = (2, 6)
(m, n) = (3, 4)
(m, n) = (3, 5)
(m, n) = (3, 6)

Answer 2

你要

@constraint(model, [i = M, j = Ni[i]], x[i] <= y[j])

以下是相关文档： https://www.juliaopt.org/JuMP.jl/stable/constraints/#Constraint-containers-1