Search code examples
julia-jump

juMP - use variable defined in sum range

I am trying to define a constraint containing summation over two indices, k and t.

for i in data.I    
    for j in 1:length(data.P[i])
        @constraint(m, w[i, j, length(data.T[data.P[i][j]])]/(1+sum(data.A[i][k][t] for k in 1:length(data.P[i]), t in data.T[data.P[i][k]])) <= s[i, j])
    end
end

I get the following error in running the code:

ERROR: LoadError: UndefVarError: k not defined

I have implemented the same model in OPL for CPLEX in the same way, and this was not an issue. Am I not allowed to introduce such variable as an index in the summation, then use it subsequently as an index to an array within the same sum() as I am trying to do above?

Solution

  • This is a question of Julia syntax:

    julia> sum(i+j for i in 1:3, j in 1:i)
ERROR: UndefVarError: i not defined

julia> sum(i+j for i in 1:3 for j in 1:i)
24

    The same should hold for JuMP.