Share ForwardDiff tag between models?

[KristofferC]

As it is right now, each model gets it's own ForwardDiff tag:

ModelBaseEcon.jl/src/evaluation.jl

Line 149 in 7a7dfa8

struct MyTag end

.

This means that if you have two models, most methods must be compiled twice due to the type of Dual numbers changing due to the changing tag. I don't see a reason why the tag could not be defined inside ModelBaseEcon itself and then shared among the models. The reason for having the tag at all is to prevent "perturbation confusion" (JuliaDiff/ForwardDiff.jl#83) but that doesn't seem (at least to me) to apply here.

That would mean that all the precompile stuff at

ModelBaseEcon.jl/src/evaluation.jl

Lines 22 to 54 in 7a7dfa8

	function precompilefuncs(resid, RJ, ::Val{N}, tag) where {N}
	ccall(:jl_generating_output, Cint, ()) == 1 || return nothing
	# tag = MyTag # ForwardDiff.Tag{resid,Float64}
	dual = ForwardDiff.Dual{tag,Float64,N}
	duals = Array{dual,1}
	cfg = ForwardDiff.GradientConfig{tag,Float64,N,duals}
	mdr = DiffResults.MutableDiffResult{1,Float64,Tuple{Array{Float64,1}}}
	precompile(resid, (Array{Float64,1},)) || error("precompile")
	precompile(resid, (duals,)) || error("precompile")
	precompile(RJ, (Array{Float64,1},)) || error("precompile")
	for pred in Symbol[:isinf, :isnan, :isfinite, :iseven, :isodd, :isreal, :isinteger, :-, :+, :log, :exp]
	pred ∈ (:iseven, :isodd) || precompile(getfield(Base, pred), (Float64,)) || error("precompile")
	precompile(getfield(Base, pred), (dual,)) || error("precompile")
	end
	for pred in Symbol[:isequal, :isless, :<, :>, :(==), :(!=), :(<=), :(>=), :+, :-, :*, :/, :^]
	precompile(getfield(Base, pred), (Float64, Float64)) || error("precompile")
	precompile(getfield(Base, pred), (dual, Float64)) || error("precompile")
	precompile(getfield(Base, pred), (Float64, dual)) || error("precompile")
	precompile(getfield(Base, pred), (dual, dual)) || error("precompile")
	end
	precompile(ForwardDiff.extract_gradient!, (Type{tag}, mdr, dual)) || error("precompile")
	precompile(ForwardDiff.vector_mode_gradient!, (mdr, typeof(resid), Array{Float64,1}, cfg)) || error("precompile")
	# precompile(Tuple{typeof(ForwardDiff.extract_gradient!), Type{tag}, mdr, dual}) || error("precompile")
	# precompile(Tuple{typeof(ForwardDiff.vector_mode_gradient!), mdr, resid, Array{Float64, 1}, cfg}) || error("precompile")
	return nothing
	end

could instead be compiled into ModelBaseEcon (for values of N from 1 to the max chunk size) instead of for each model.

[KristofferC]

I made an attempt in #38

[bbejanov]

Thanks for the suggestion!
#38 has been merged, so this issue is now resolved.