Model/variable copy error in JuMP 0.18

Specific Domains Optimization (Mathematical)
1

I created a simple model and tried to copy and modify.

using JuMP, Clp

m = Model(solver=ClpSolver())
set_A = [(1,2), (2,3)]
@variable(m, x[(i,j) in set_A]>=0)
@objective(m, Max, sum(x[(i,j)] for (i,j) in set_A) )
@constraint(m, x[(1,2)]<=10)
@constraint(m, x[(2,3)]<=10)
solve(m)
@show getvalue(x)

m2 = copy(m)
x2 = copy(x, m2)
@constraint(m2, x2[(1,2)]<=1)
@constraint(m2, x2[(2,3)]<=1)
solve(m2)
@show getvalue(x2)

The last line creates an error. When tuples were not used in the variable definition, it works fine.

getvalue(x) = x: 1 dimensions:
[(1, 2)] = 10.0
[(2, 3)] = 10.0
ERROR: LoadError: 
Stacktrace:
 [1] getindex(::ObjectIdDict, ::JuMP.JuMPArray{JuMP.Variable,1,Tuple{Array{Tuple{Int64,Int64},1}}}) at ./associative.jl:363
 [2] _map(::Function, ::JuMP.JuMPArray{JuMP.Variable,1,Tuple{Array{Tuple{Int64,Int64},1}}}) at /Users/chkwon/.julia/v0.6/JuMP/src/JuMPContainer.jl:162
 [3] getvalue(::JuMP.JuMPArray{JuMP.Variable,1,Tuple{Array{Tuple{Int64,Int64},1}}}) at /Users/chkwon/.julia/v0.6/JuMP/src/JuMPContainer.jl:114
 [4] include_from_node1(::String) at ./loading.jl:576
 [5] include(::String) at ./sysimg.jl:14SYSTEM: show(lasterr) caused an error
AssertionError("j isa Array{Variable}")

Stacktrace:
 [1] getindex(::ObjectIdDict, ::JuMP.JuMPArray{JuMP.Variable,1,Tuple{Array{Tuple{Int64,Int64},1}}}) at ./associative.jl:363
 [2] _map(::Function, ::JuMP.JuMPArray{JuMP.Variable,1,Tuple{Array{Tuple{Int64,Int64},1}}}) at /Users/chkwon/.julia/v0.6/JuMP/src/JuMPContainer.jl:162
 [3] getvalue(::JuMP.JuMPArray{JuMP.Variable,1,Tuple{Array{Tuple{Int64,Int64},1}}}) at /Users/chkwon/.julia/v0.6/JuMP/src/JuMPContainer.jl:114
 [4] include_from_node1(::String) at ./loading.jl:576
 [5] include(::String) at ./sysimg.jl:14
 [6] eval(::Module, ::Any) at ./boot.jl:235
 [7] eval_user_input(::Any, ::Base.REPL.REPLBackend) at ./REPL.jl:66
 [8] macro expansion at ./REPL.jl:97 [inlined]
 [9] (::Base.REPL.##1#2{Base.REPL.REPLBackend})() at ./event.jl:73

Is this a bug?

2

The error is from when it tries to print x2.

It probably shouldn’t error, but you can go x2 = m2[:x] instead of the copy.

It looks like @blegat last touched this stuff:
https://github.com/JuliaOpt/JuMP.jl/issues/1019
https://github.com/JuliaOpt/JuMP.jl/pull/1020

3

copy(x, m2) is not meant to be called manually, it is already called in copy(m).
https://github.com/JuliaOpt/JuMP.jl/blob/d3814460359b324afc47ac99a8342927b4082e32/src/JuMP.jl#L299-L304
As you can see, inside copy(m), it also copies, the varData entries. If you call copy(x, m2) manually, you also need to do m2.varData[x2] = m.varData[x]

4

Thanks @odow and @blegat.

Either

x2 = m2[:x]

or

x2 = copy(x, m2);
m2.varData[x2] = m.varData[x]

works. I think I should stick to the first one.