solveRobust( ... ) vs solve(...) with multiple dispatch? about jumper.jl

[IainNZ]

Can't be done (yet)
Robust models are JuMP models with an "extension".

function RobustModel(;solver=nothing,cutsolver=nothing)
    m = Model(solver=solver)
    m.ext[:Robust] = RobustData(cutsolver)
    return m
end

Alternatives that would let you do multiple dispatch including using an AbstractModel from which Model and a hypothetical RobustModel inherit from is one option, another was making Model parametric. Both had issues...
This is something @mlubin and I talked about a lot, and this "extension" mechanism was the best we could do without compromising any JuMP speed. Somewhat related to JuliaLang/julia#4935

[vgupta1]

I noticed that... Do you know if the language extension is coming soon?
(i.e. requiring abstract types to have certain members?)

Alternatively, although it seems a bit dodgy, (for my own edifiaton)
couldn't you have done this?

type RobustModel <: Model
    m  #This is actually a model
     rd #this is the robust data and extension stuff
end

In other words, Robust models implement BOTH "is a" and "has a" in the
inheritance scheme?

---

Vishal Gupta
PhD Candidate, 2014
Operations Research Center
Massachusetts Institute of Technology
www.mit.edu/~vgupta1/

On Thu, Apr 10, 2014 at 9:50 PM, Iain Dunning [email protected]:

Can't be done (yet)
Robust models are JuMP models with an "extension".

function RobustModel(;solver=nothing,cutsolver=nothing)
m = Model(solver=solver)
m.ext[:Robust] = RobustData(cutsolver)
return m
end

Alternatives that would let you do multiple dispatch including using an
AbstractModel from which Model and a hypothetical RobustModel inherit from
is one option, another was making Model parametric. Both had issues...
This is something @mlubin https://github.com/mlubin and I talked about
a lot, and this "extension" mechanism was the best we could do without
compromising any JuMP speed. Somewhat related to JuliaLang/julia#4935JuliaLang/julia#4935

Reply to this email directly or view it on GitHubhttps://github.com//issues/13#issuecomment-40163671
.

[mlubin]

The issue is that variables contain a reference to their parent model, which needs to be a Model. We tried making variables parametric on the model type, but that led to Julia's version of C++ template hell. Having different model types also makes extensions mutually exclusive.

[mlubin]

Also you can't inherit from concrete types in Julia. Model would need to be an abstract type.