GAMSFiles

Parse files for General Algebraic Modeling System and return Julia expressions. As a matter of practicality, the only current purpose of this package is to parse the problem files from Rios & Sahinidis. Please reach out if you'd like to help extend this package.

Demo

Suppose you have a local file, problem.gms, in GAMS format. Then

julia> using GAMSFiles

# This parses the file, returning an expression that defines a module
# together with information about starting point and bounds
julia> modex, axs = parsegams(Module, "problem.gms");

# Create the module
julia> m = eval(modex)
Main.problem

# Extract the objective function
julia> f = getglobal(m, :objective)
objective (generic function with 1 method)

# Get the initial point and the variable bounds
julia> x0, lo, hi, isfixed = axs
([1.0, 2.0, 1.0, 1.0, 4.0, 3.0], [-Inf, -Inf, -Inf, -Inf, -Inf, -Inf], [Inf, Inf, Inf, Inf, Inf, Inf], [false, false, false, false, false, false])

# Try evaluating the objective
julia> f(x0)
1.624842441282596

x0 is the default initial point. lo contains the variable lower bounds, and hi the variable upper bounds. isfixed is true for variables that should be held constant.