write the model to text file

[manarjar]

Hello, is it possible to write the model in each node to a text file just like JuMP.write_to_file function?

[etatara]

If you want to serialize a graph, it's probably easiest to just use JLD2 to write the objects directly. The JuMP.write_to_file is not supported on Plasmo models and think it would be problematic since it would only give you the JuMP model and not the graph representation. If you want to print out the model text then you could try something like the example below (may need to modify depending on what you need) which works on Plasmo 0.5.4. I think it would be great to have a Plasmo API that provides something similar.

function write_optigraph(graph::Plasmo.OptiGraph, filename::AbstractString)
    
    # Large enough to print all constraint values
    JuMP._CONSTRAINT_LIMIT_FOR_PRINTING[]=10000

    open(filename,"w") do f
        write(f, "Objective Function:\n")
        write(f, "$(objective_function(graph))\n\n")

        write(f, "Graph Nodes: \n")
        for node in graph.optinodes
            s = ""
            s = s*node.label*"\n"
            s = s*string(node.model)
            # s = s*string(node.partial_linkconstraints)*"\n"
            write(f, s)
        end

        write(f, "Link constraints: \n")
        for lc in linkconstraints(graph)
            s = string(lc)*"\n"
            write(f, s)
        end
    
	end

end

[dlcole3]

@manarjar, as @etatara said, JuMP.write_to_file is currently not supported for Plasmo, and I agree that what is exported from this function would essentially be the JuMP model, and you would not be able to load the model back in as an OptiGraph. I think @etatara's approach above will allow you to keep more of the graph structure saved when you export.

That said, if you would like to export the model anyway with write_to_file, you can effectively do this with the following code snippet:

using JuMP, Plasmo

g = OptiGraph()
@optinode(g, n)
@variable(n, x[1:10]>= 0)

filename = (@__DIR__)*"/test.lp"
m = MOI.FileFormats.Model(filename=filename)
f = () -> MOI.FileFormats.Model(filename=filename)

inner = MOI.instantiate(f)

moi_g_model = g.backend.moi_backend.model_cache.model

inner_map = MOI.copy_to(inner, moi_g_model)
ub = JuMP.unsafe_backend(inner)

MOI.write_to_file(ub, filename)

I have only tried this on .lp files, but it would presumably work for other file types. Similar to etatara's code above, this will export your model as text that you can view, but it won't include the graph structure like etatara's answer does above.