Make normalization more AD friendly (#148)

Author: avik-pal

Project.toml

@@ -1,7 +1,7 @@
 name = "Lux"
 uuid = "b2108857-7c20-44ae-9111-449ecde12c47"
 authors = ["Avik Pal <[email protected]> and contributors"]
-version = "0.4.20"
+version = "0.4.21"
 
 [deps]
 Adapt = "79e6a3ab-5dfb-504d-930d-738a2a938a0e"

src/autodiff.jl

@@ -10,17 +10,23 @@ ChainRulesCore.@non_differentiable glorot_uniform(::Any...)
 ChainRulesCore.@non_differentiable check_use_cuda()
 ChainRulesCore.@non_differentiable istraining(::Any)
 ChainRulesCore.@non_differentiable _get_norm_except_dims(::Any, ::Any)
+ChainRulesCore.@non_differentiable _affine(::Any)
+ChainRulesCore.@non_differentiable _track_stats(::Any)
+ChainRulesCore.@non_differentiable _copy_autodiff_barrier(::Any)
 
 # NNlib Functions
-function ChainRulesCore.rrule(::typeof(batchnorm), g::CuArray{T}, b::CuArray{T},
-                              x::Union{CuArray{T, 4}, CuArray{T, 5}}, running_mean,
-                              running_var, momentum; kwargs...) where {T <: CUDNNFloat}
-    y = batchnorm(g, b, x, running_mean, running_var, momentum; kwargs...)
-    function batchnorm_pullback(dy)
-        dg, db, dx = ∇batchnorm(g, b, x, dy, running_mean, running_var, momentum; kwargs...)
-        return NoTangent(), dg, db, dx, NoTangent(), NoTangent(), NoTangent()
+function ChainRulesCore.rrule(::typeof(_batchnorm), g::CuArray{T}, b::CuArray{T},
+                              x::Union{CuArray{T, 2}, CuArray{T, 4}, CuArray{T, 5}},
+                              running_mean, running_var, momentum, epsilon,
+                              training) where {T <: CUDNNFloat}
+    y = _batchnorm(g, b, x, running_mean, running_var, momentum, epsilon, training)
+    function _batchnorm_pullback(dy)
+        dg, db, dx = ∇batchnorm(g, b, x, unthunk(dy), running_mean, running_var, momentum;
+                                eps=epsilon, training=training)
+        return NoTangent(), dg, db, dx, NoTangent(), NoTangent(), NoTangent(), NoTangent(),
+               NoTangent()
     end
-    return y, batchnorm_pullback
+    return y, _batchnorm_pullback
 end
 
 function ChainRulesCore.rrule(::typeof(dropout), rng::AbstractRNG, x::AbstractArray{T, N},
@@ -59,6 +65,9 @@ function ChainRulesCore.rrule(::typeof(merge), nt1::NamedTuple{F1},
         dnt2 = NamedTuple((f2 => getproperty(dy, f2) for f2 in F2))
         return (NoTangent(), dnt1, dnt2)
     end
+    function merge_pullback(dy::Union{NoTangent, ZeroTangent})
+        return (NoTangent(), NoTangent(), NoTangent())
+    end
     return y, merge_pullback
 end
 
@@ -89,6 +98,11 @@ function ChainRulesCore.rrule(::typeof(collect), v::Vector)
     return y, collect_pullback
 end
 
+function ChainRulesCore.rrule(::typeof(copy), x)
+    copy_pullback(dy) = (NoTangent(), dy)
+    return copy(x), copy_pullback
+end
+
 # Zygote Fixes
 function Zygote.accum(x::ComponentArray, ys::ComponentArray...)
     return ComponentArray(Zygote.accum(getdata(x), getdata.(ys)...), getaxes(x))

src/layers/normalize.jl

@@ -1,5 +1,8 @@
 abstract type AbstractNormalizationLayer{affine, track_stats} <: AbstractExplicitLayer end
 
+@inline _affine(l::AbstractNormalizationLayer{A, T}) where {A, T} = A
+@inline _track_stats(l::AbstractNormalizationLayer{A, T}) where {A, T} = T
+
 """
     BatchNorm(chs::Integer, activation=identity; init_bias=zeros32, init_scale=ones32,
               affine=true, track_stats=true, epsilon=1f-5, momentum=0.1f0)
@@ -93,28 +96,25 @@ function BatchNorm(chs::Int, activation=identity; init_bias=zeros32, init_scale=
                                                           chs, init_bias, init_scale)
 end
 
-function initialparameters(rng::AbstractRNG, l::BatchNorm{affine}) where {affine}
-    if affine
+function initialparameters(rng::AbstractRNG, l::BatchNorm)
+    if _affine(l)
         return (scale=l.init_scale(rng, l.chs), bias=l.init_bias(rng, l.chs))
     else
         return (scale=nothing, bias=nothing)
     end
 end
 
-function initialstates(rng::AbstractRNG,
-                       l::BatchNorm{affine, track_stats}) where {affine, track_stats}
-    return if track_stats
-        (running_mean=zeros32(rng, l.chs), running_var=ones32(rng, l.chs),
-         training=Val(true))
+function initialstates(rng::AbstractRNG, l::BatchNorm)
+    if _track_stats(l)
+        return (running_mean=zeros32(rng, l.chs), running_var=ones32(rng, l.chs),
+                training=Val(true))
     else
-        (running_mean=nothing, running_var=nothing, training=Val(true))
+        return (running_mean=nothing, running_var=nothing, training=Val(true))
     end
 end
 
-parameterlength(l::BatchNorm{affine}) where {affine} = affine ? (l.chs * 2) : 0
-function statelength(l::BatchNorm{affine, track_stats}) where {affine, track_stats}
-    return (track_stats ? 2 * l.chs : 0) + 1
-end
+parameterlength(l::BatchNorm) = _affine(l) ? (l.chs * 2) : 0
+statelength(l::BatchNorm) = (_track_stats(l) ? 2 * l.chs : 0) + 1
 
 function (BN::BatchNorm)(x::AbstractArray{T, N}, ps, st::NamedTuple) where {T, N}
     x_normalized, xmean, xvar = normalization(x, st.running_mean, st.running_var, ps.scale,
@@ -127,42 +127,42 @@ function (BN::BatchNorm)(x::AbstractArray{T, N}, ps, st::NamedTuple) where {T, N
     return x_normalized, st
 end
 
-function (BN::BatchNorm{affine, track_stats})(x::Union{CuArray{T, 2}, CuArray{T, 4},
-                                                       CuArray{T, 5}}, ps,
-                                              st::NamedTuple) where {
-                                                                     T <:
-                                                                     Union{Float32, Float64
-                                                                           }, affine,
-                                                                     track_stats}
+function _batchnorm(scale, bias, x, running_mean, running_var, momentum, epsilon, training)
+    return batchnorm(scale, bias, x, running_mean, running_var, momentum; eps=epsilon,
+                     training=training)
+end
+
+function (BN::BatchNorm)(x::Union{CuArray{T, 2}, CuArray{T, 4}, CuArray{T, 5}}, ps,
+                         st::NamedTuple) where {T <: Union{Float32, Float64}}
     # NNlibCUDA silently updates running_mean and running_var so copying them
     if istraining(st)
-        running_mean2 = track_stats ? copy(st.running_mean) : nothing
-        running_var2 = track_stats ? copy(st.running_var) : nothing
+        running_mean2 = _track_stats(BN) ? _copy_autodiff_barrier(st.running_mean) : nothing
+        running_var2 = _track_stats(BN) ? _copy_autodiff_barrier(st.running_var) : nothing
     else
-        if track_stats
-            running_mean2 = copy(st.running_mean)
-            running_var2 = copy(st.running_var)
+        if _track_stats(BN)
+            running_mean2 = _copy_autodiff_barrier(st.running_mean)
+            running_var2 = _copy_autodiff_barrier(st.running_var)
         else
             N = ndims(x)
             reduce_dims = collect([1:(N - 2); N])
             running_mean2 = mean(x; dims=reduce_dims)
             running_var2 = var(x; mean=running_mean2, dims=reduce_dims, corrected=false)
         end
     end
-    res = BN.activation.(batchnorm(affine ? ps.scale : nothing, affine ? ps.bias : nothing,
-                                   x, running_mean2, running_var2, BN.momentum;
-                                   eps=BN.epsilon, training=istraining(st)))
-    if track_stats
+    res = BN.activation.(_batchnorm(_affine(BN) ? ps.scale : nothing,
+                                    _affine(BN) ? ps.bias : nothing, x, running_mean2,
+                                    running_var2, BN.momentum, BN.epsilon, istraining(st)))
+    if _track_stats(BN)
         st = merge(st, (running_mean=running_mean2, running_var=running_var2))
     end
     return res, st
 end
 
-function Base.show(io::IO, l::BatchNorm{affine, track_stats}) where {affine, track_stats}
+function Base.show(io::IO, l::BatchNorm)
     print(io, "BatchNorm($(l.chs)")
     (l.activation == identity) || print(io, ", $(l.activation)")
-    print(io, ", affine=$(affine)")
-    print(io, ", track_stats=$(track_stats)")
+    print(io, ", affine=$(_affine(l))")
+    print(io, ", track_stats=$(_track_stats(l))")
     return print(io, ")")
 end
 
@@ -281,29 +281,26 @@ function GroupNorm(chs::Integer, groups::Integer, activation=identity; init_bias
                                                           groups)
 end
 
-function initialparameters(rng::AbstractRNG, l::GroupNorm{affine}) where {affine}
-    if affine
+function initialparameters(rng::AbstractRNG, l::GroupNorm)
+    if _affine(l)
         return (scale=l.init_scale(rng, l.chs), bias=l.init_bias(rng, l.chs))
     else
         return (scale=nothing, bias=nothing)
     end
 end
 
-function initialstates(rng::AbstractRNG,
-                       l::GroupNorm{affine, track_stats}) where {affine, track_stats}
-    return if track_stats
+function initialstates(rng::AbstractRNG, l::GroupNorm)
+    return if _track_stats(l)
         (running_mean=zeros32(rng, l.groups), running_var=ones32(rng, l.groups),
          training=Val(true))
     else
         (running_mean=nothing, running_var=nothing, training=Val(true))
     end
 end
 
-parameterlength(l::GroupNorm{affine}) where {affine} = affine ? (l.chs * 2) : 0
+parameterlength(l::GroupNorm) = _affine(l) ? (l.chs * 2) : 0
 
-function statelength(l::GroupNorm{affine, track_stats}) where {affine, track_stats}
-    return (track_stats ? 2 * l.groups : 0) + 1
-end
+statelength(l::GroupNorm) = (_track_stats(l) ? 2 * l.groups : 0) + 1
 
 function (GN::GroupNorm)(x::AbstractArray{T, N}, ps, st::NamedTuple) where {T, N}
     sz = size(x)
@@ -318,11 +315,11 @@ function (GN::GroupNorm)(x::AbstractArray{T, N}, ps, st::NamedTuple) where {T, N
     return reshape(x_normalized, sz), st
 end
 
-function Base.show(io::IO, l::GroupNorm{affine, track_stats}) where {affine, track_stats}
+function Base.show(io::IO, l::GroupNorm)
     print(io, "GroupNorm($(l.chs), $(l.groups)")
     (l.activation == identity) || print(io, ", $(l.activation)")
-    print(io, ", affine=$(affine)")
-    print(io, ", track_stats=$(track_stats)")
+    print(io, ", affine=$(_affine(l))")
+    print(io, ", track_stats=$(_track_stats(l))")
     return print(io, ")")
 end
 

src/utils.jl

@@ -189,3 +189,6 @@ Split up `x` into `N` equally sized chunks (along dimension `1`).
 
 # Val utilities
 get_known(::Val{T}) where {T} = T
+
+# Copy and don't allow gradient propagation
+_copy_autodiff_barrier(x) = copy(x)