Ok, thanks for the update on the syntax. I think isapprox might be a better way to do what I want since I’ve got to use an equation as the input, and round() appears to only work with simple arithmetic.

However, I’m still having trouble making it do what I want it to.

@constraint(m, [i = 1:nREGION], isapprox((PRODUCE[i]-CONSUME[i])*10^9 + sum(VolShip[i,j] for j=1:nREGION) - sum(VolShip[j,i] for j=1:nREGION), 0))

spits out this error:

ERROR: LoadError: LoadError: **Unrecognized sense isapprox**

Stacktrace:

[1] _canonicalize_sense(::Symbol) at C:\Users\kirbo.julia\packages\JuMP\PbnIJ\src\macros.jl:303

[2] @constraint(::LineNumberNode, ::Module, ::Vararg{Any,N} where N) at C:\Users\kirbo.julia\packages\JuMP\PbnIJ\src\macros.jl:484

Essentially I’ve got a mass balance problem with multiple options. right now I’ve got it reduced to 3 nodes, but I want to expand. It worked with three briefly before I made inputs with decimal spaces - now Julia’s excessive decimal places screwed things up.

Is there a better function for dealing with open ended macros like JuMP?