move enzyme to extension (#2467)

Project.toml

@@ -6,7 +6,6 @@ version = "0.14.17"
 Adapt = "79e6a3ab-5dfb-504d-930d-738a2a938a0e"
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
 Compat = "34da2185-b29b-5c13-b0c7-acf172513d20"
-Enzyme = "7da242da-08ed-463a-9acd-ee780be4f1d9"
 Functors = "d9f16b24-f501-4c13-a1f2-28368ffc5196"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 MLUtils = "f1d291b0-491e-4a28-83b9-f70985020b54"
@@ -26,13 +25,15 @@ Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 [weakdeps]
 AMDGPU = "21141c5a-9bdb-4563-92ae-f87d6854732e"
 CUDA = "052768ef-5323-5732-b1bb-66c8b64840ba"
+Enzyme = "7da242da-08ed-463a-9acd-ee780be4f1d9"
 Metal = "dde4c033-4e86-420c-a63e-0dd931031962"
 cuDNN = "02a925ec-e4fe-4b08-9a7e-0d78e3d38ccd"
 
 [extensions]
 FluxAMDGPUExt = "AMDGPU"
 FluxCUDAExt = "CUDA"
 FluxCUDAcuDNNExt = ["CUDA", "cuDNN"]
+FluxEnzymeExt = "Enzyme"
 FluxMetalExt = "Metal"
 
 [compat]

ext/FluxEnzymeExt/FluxEnzymeExt.jl

@@ -0,0 +1,47 @@
+module FluxEnzymeExt
+
+using Flux
+import Flux.Train: train!, _rule_to_state
+import Flux.Optimise
+import Optimisers
+import Enzyme
+using Enzyme: EnzymeRules, Active, Const, Duplicated, autodiff, ReverseWithPrimal
+using ProgressLogging: @withprogress, @logprogress
+
+_make_zero_internal!(x::AbstractArray) = fill!(x, 0)
+_make_zero_internal!(x) = x
+_make_zero!(model) = fmap(_make_zero_internal!, model)
+
+_applyloss(loss, model, d...) = loss(model, d...)
+
+EnzymeRules.inactive(::typeof(Flux.Losses._check_sizes), args...) = true
+
+using Flux: _old_to_new  # from src/deprecations.jl
+train!(loss, model::Duplicated, data, opt::Optimise.AbstractOptimiser; cb=nothing) =
+  train!(loss, model, data, _old_to_new(opt); cb)
+
+function train!(loss, model::Duplicated, data, rule::Optimisers.AbstractRule; cb = nothing)
+  train!(loss, model, data, _rule_to_state(model, rule); cb)
+end
+
+function train!(loss, model::Duplicated, data, opt; cb = nothing)
+  isnothing(cb) || error("""train! does not support callback functions.
+                            For more control use a loop with `gradient` and `update!`.""")
+  @withprogress for (i,d) in enumerate(data)
+    d_splat = d isa Tuple ? d : (d,)
+
+    _make_zero!(model.dval)
+    _, l = Enzyme.autodiff(ReverseWithPrimal, _applyloss, 
+                           Active, Const(loss), model, map(Const, d_splat)...)
+
+    if !isfinite(l)
+      throw(DomainError(lazy"Loss is $l on data item $i, stopping training"))
+    end
+    opt, model2 = Optimisers.update!(opt, model.val, model.dval)
+    model = Duplicated(model2, model.dval)
+
+    @logprogress Base.haslength(data) ? i/length(data) : nothing
+  end
+end
+
+end # FluxEnzymeExt

src/deprecations.jl

@@ -109,8 +109,7 @@ train!(loss, ps::Params, data, opt::Optimisers.AbstractRule; cb=nothing) = error
 
 train!(loss, model, data, opt::Optimise.AbstractOptimiser; cb=nothing) =
   train!(loss, model, data, _old_to_new(opt); cb)
-train!(loss, model::Enzyme.Duplicated, data, opt::Optimise.AbstractOptimiser; cb=nothing) =
-  train!(loss, model, data, _old_to_new(opt); cb)
+
 
 # Next, to use the new `setup` with the still-exported old-style `Adam` etc:
 import .Train: setup

src/functor.jl

@@ -3,7 +3,6 @@ using  LinearAlgebra: Cholesky
 using Zygote: IdSet
 import Functors: Functors, @functor, functor, fmap, isleaf
 using SparseArrays: AbstractSparseArray
-using Enzyme
 
 """
     testmode!(model, [mode]) -> model

src/losses/utils.jl

@@ -1,4 +1,3 @@
-import Enzyme
 
 """
     xlogx(x)
@@ -38,4 +37,3 @@ end
 _check_sizes(ŷ, y) = nothing  # pass-through, for constant label e.g. y = 1
 
 ChainRulesCore.@non_differentiable _check_sizes(ŷ::Any, y::Any)
-Enzyme.EnzymeRules.inactive(::typeof(_check_sizes), args...) = true

src/train.jl

@@ -5,7 +5,6 @@ using Optimisers: Optimisers
 using Functors: fmap, fmapstructure
 using ..Flux: Flux # used only in docstring 
 import ..Flux.Optimise: train!, update!  # during 0.13, we add methods to the old functions
-import Enzyme
 
 export setup, train!
 
@@ -53,12 +52,6 @@ function setup(rule::Optimisers.AbstractRule, model)
     state
 end
 
-_make_zero_internal!(x::AbstractArray) = fill!(x, 0)
-_make_zero_internal!(x) = x
-_make_zero!(model) = fmap(_make_zero_internal!, model)
-
-_applyloss(loss, model, d...) = loss(model, d...)
-
 """
     train!(loss, model, data, opt_state)
 
@@ -67,7 +60,7 @@ according to a particular optimisation rule encoded in `opt_state`.
 Iterates through `data` once, evaluating for each `d in data` either
 `loss(model, d...)` if `d isa Tuple`, or else `loss(model, d)` for other `d`.
 
-If `model` is an Enzyme.Duplicated, gradients will be computed with Enzyme,
+If `model` is an Enzyme.Duplicated and `Enzyme.jl` is loaded, gradients will be computed with Enzyme,
 otherwise they will be computed with Zygote.
 
 For example, with these definitions...
@@ -122,32 +115,12 @@ function train!(loss, model, data, opt; cb = nothing)
     @logprogress Base.haslength(data) ? i/length(data) : nothing
   end
 end
-function train!(loss, model::Enzyme.Duplicated, data, opt; cb = nothing)
-  isnothing(cb) || error("""train! does not support callback functions.
-                            For more control use a loop with `gradient` and `update!`.""")
-  @withprogress for (i,d) in enumerate(data)
-    d_splat = d isa Tuple ? d : (d,)
-
-    _make_zero!(model.dval)
-    _, l = Enzyme.autodiff(Enzyme.ReverseWithPrimal, _applyloss, Enzyme.Active, Enzyme.Const(loss), model, map(Enzyme.Const, d_splat)...)
-
-    if !isfinite(l)
-      throw(DomainError(lazy"Loss is $l on data item $i, stopping training"))
-    end
-    opt, model2 = Optimisers.update!(opt, model.val, model.dval)
-    model = Enzyme.Duplicated(model2, model.dval)
 
-    @logprogress Base.haslength(data) ? i/length(data) : nothing
-  end
-end
 
 # This method let you use Optimisers.Descent() without setup, when there is no state
 function train!(loss, model, data, rule::Optimisers.AbstractRule; cb = nothing)
   train!(loss, model, data, _rule_to_state(model, rule); cb)
 end
-function train!(loss, model::Enzyme.Duplicated, data, rule::Optimisers.AbstractRule; cb = nothing)
-  train!(loss, model, data, _rule_to_state(model, rule); cb)
-end
 
 function _rule_to_state(model, rule::Optimisers.AbstractRule)
   state = setup(rule, model)

test/ext_enzyme/enzyme.jl

@@ -1,15 +1,12 @@
 using Test
 using Flux
 
-using Enzyme
+using Enzyme: Enzyme, make_zero, Active, Duplicated, ReverseWithPrimal
+
 using Functors
 using FiniteDifferences
 using CUDA
 
-_make_zero(x::Union{Number,AbstractArray}) = zero(x)
-_make_zero(x) = x
-make_zero(model) = fmap(_make_zero, model)
-## make_differential(model) = fmapstructure(make_zero, model) # NOT SUPPORTED, See https://github.com/EnzymeAD/Enzyme.jl/issues/1329
 
 function gradient_fd(f, x...)
     x = [cpu(x) for x in x]

test/train.jl

@@ -4,10 +4,10 @@ import Optimisers
 
 using Test
 using Random
-using Enzyme
+import Enzyme
 
 function train_enzyme!(fn, model, args...; kwargs...)
-    Flux.train!(fn, Duplicated(model, Enzyme.make_zero(model)), args...; kwargs...)
+  Flux.train!(fn, Enzyme.Duplicated(model, Enzyme.make_zero(model)), args...; kwargs...)
 end
 
 for (trainfn!, name) in ((Flux.train!, "Zygote"), (train_enzyme!, "Enzyme"))