dual variable

[mahsap58]

Hello, I want to get the dual variable of following constraint, I used getdual(con1) but i faced with an error. please help me to get the dual variables of this constraint.
@constraint(model, con1[i = 1:I], sum( x[i,k] * y[k] for k=1:K) == b[i])

[oschulz]

Hello @mahsap58, I'm not quite sure where ValueShapes fits into this. Could you elaborate?

[mahsap58]

My total code are as below; i have one minimization problem and the second is maximization within a while loop I solve the first, get the dual of it and put it in the second model (i called it c[i], c[i] is the dual variable of constraint of first model), after solving the second model i get the asol and attach it to the x, x is initial solution of the first model. now i need c as the dual variable of first model.
using JuMP
using Gurobi
K=5,I=5
x=[4 0 0 0 0
0 2 0 0 0
0 0 2 0 0
0 0 0 2 0
0 0 0 0 1]
w=[11 15 19 23 27]
b=[97 140 191 85 129]
reducedCost=-Inf
while reducedCost < 0
model = Model(with_optimizer(Gurobi.Optimizer))
@variable(model, 0 <= y[1:K])
@objective(model, Min, sum(y[k] for k = 1:K))
@constraint(model, con1[i = 1:I], sum( x[i,k] * y[k] for k=1:K) == b[i])
optimize!(model)
termination_status(model)
optval = objective_value(model)
ysol = value.(y)
println("Optimal Value = $optval")

@variable(model, 0 <= a[1:I], int)
@objective(model, Max, sum(c[i] * a[i] for i = 1:I))
@constraint(model, con1[i = 1:I], sum( w[i] * a[i] for i=1:I) <= 50)
optimize!(model)
termination_status(model)
reducedCost = objective_value(model)
asol = value.(a)
println("Optimal Value = $optval")
reducedCost=1-reducedCost;
if reducedCost<-0.001;
x = [x,asol];
K=K+1;
end

[oschulz]

@mahsap58, could it be that you posted to the wrong repo? This one is about the ValueShapes package, not JuMP and/or Gurobi.

[mahsap58]

i tried to install ValueShapes using Pkg.add("ValueShapes") and i think there was an error and it does not installed and this is the error after running the code
Failed to precompile ValueShapes

[oschulz]

Hm, that is strange - I can't reproduce the error, and testing on Travis on Linux, OS-X and Windows also runs fine (see https://travis-ci.com/oschulz/ValueShapes.jl/builds/145010659). Could you try again with a clean, empty Julia environment (empty ".julia" directory)?

[mahsap58]

what is this error? please tell me how can i install deps.jl
No deps.jl file could be found. Please try running Pkg.build("Arpack").
Currently, the build command might fail when Julia has been built from source
and the recommendation is to use the official binaries from julialang.org.
For more info see JuliaLinearAlgebra/Arpack.jl#5.

[oschulz]

@mahsap58, I get the impression that you're looking for general help on how to use Julia and Julia packages not related to ValueShapes. A better place for that would be https://discourse.julialang.org/ . Could you please direct your questions there?