Simplify trainable, functor and Parallel (#1862)

* simple functor Chain

* simplify Maxout

* fix show as a result

* trainable always a NamedTuple

* Parallel: delete trainable, call combiner once

* fixup

* fix tests for Flux.modules

src/deprecations.jl

@@ -36,4 +36,3 @@ zeros32(::Type, dims...) = throw(ArgumentError("Flux.zeros32 is always Float32,
 
 
 # v0.13 deprecations
-@deprecate Maxout(layers::Tuple) Maxout(layers...)

src/layers/basic.jl

@@ -28,29 +28,30 @@ julia> m2(x) == (m2[:dec] ∘ m2[:enc])(x)
 true
 ```
 """
-struct Chain{T}
+struct Chain{T<:Union{Tuple, NamedTuple}}
   layers::T
-  Chain(xs...) = new{typeof(xs)}(xs)
-  function Chain(; kw...)
-    :layers in Base.keys(kw) && throw(ArgumentError("a Chain cannot have a named layer called `layers`"))
-    isempty(kw) && return new{Tuple{}}(())
-    new{typeof(values(kw))}(values(kw))
-  end
+end
+
+Chain(xs...) = Chain(xs)
+function Chain(; kw...)
+  :layers in Base.keys(kw) && throw(ArgumentError("a Chain cannot have a named layer called `layers`"))
+  isempty(kw) && return Chain(())
+  Chain(values(kw))
 end
 
 @forward Chain.layers Base.getindex, Base.length, Base.first, Base.last,
   Base.iterate, Base.lastindex, Base.keys
 
-functor(::Type{<:Chain}, c) = c.layers, ls -> Chain(ls...)
+@functor Chain
 
 applychain(::Tuple{}, x) = x
 applychain(fs::Tuple, x) = applychain(tail(fs), first(fs)(x))
 
 (c::Chain)(x) = applychain(Tuple(c.layers), x)
 
-Base.getindex(c::Chain, i::AbstractArray) = Chain(c.layers[i]...)
-Base.getindex(c::Chain{<:NamedTuple}, i::AbstractArray) = 
-  Chain(; NamedTuple{Base.keys(c)[i]}(Tuple(c.layers)[i])...)
+Base.getindex(c::Chain, i::AbstractArray) = Chain(c.layers[i])
+Base.getindex(c::Chain{<:NamedTuple}, i::AbstractArray) =
+  Chain(NamedTuple{Base.keys(c)[i]}(Tuple(c.layers)[i]))
 
 function Base.show(io::IO, c::Chain)
   print(io, "Chain(")
@@ -246,29 +247,23 @@ julia> Flux.outputsize(m3, (5, 11))
 (7, 11)
 ```
 """
-struct Maxout{FS<:Tuple}
-  over::FS
-  Maxout(layers...) = new{typeof(layers)}(layers)
-end
-
-function Maxout(f::Function, n_alts::Integer)
-  over = Tuple(f() for _ in 1:n_alts)
-  return Maxout(over...)
+struct Maxout{T<:Tuple}
+  layers::T
 end
+Maxout(layers...) = Maxout(layers)
+Maxout(f::Function, n_alts::Integer) = Maxout((f() for _ in 1:n_alts)...)
 
 @functor Maxout
 
 function (mo::Maxout)(input::AbstractArray)
   # Perhaps surprisingly, pairwise max broadcast is often faster,
   # even with Zygote. See #698 and #1794
-  mapreduce(f -> f(input), (acc, out) -> max.(acc, out), mo.over)
+  mapreduce(f -> f(input), (acc, out) -> max.(acc, out), mo.layers)
 end
 
-trainable(mo::Maxout) = mo.over
-
 function Base.show(io::IO, mo::Maxout)
   print(io, "Maxout(")
-  _show_layers(io, mo.over)
+  _show_layers(io, mo.layers)
   print(io, ")")
 end
 
@@ -415,8 +410,8 @@ end
 Create a `Parallel` layer that passes an input array to each path in
 `layers`, before reducing the output with `connection`.
 
-Called with one input `x`, this is equivalent to `reduce(connection, [l(x) for l in layers])`.
-If called with multiple inputs, they are `zip`ped with the layers, thus `Parallel(+, f, g)(x, y) = f(x) + g(y)`.
+Called with one input `x`, this is equivalent to `connection([l(x) for l in layers]...)`.
+If called with multiple inputs, one is passed to each layer, thus `Parallel(+, f, g)(x, y) = f(x) + g(y)`.
 
 Like [`Chain`](@ref), its sub-layers may be given names using the keyword constructor.
 These can be accessed by indexing: `m[1] == m[:name]` is the first layer.
@@ -451,7 +446,7 @@ julia> model2[:β] == model2[2]
 true
 ```
 """
-struct Parallel{F, T}
+struct Parallel{F, T<:Union{Tuple, NamedTuple}}
   connection::F
   layers::T
 end
@@ -461,25 +456,31 @@ function Parallel(connection; kw...)
   layers = NamedTuple(kw)
   if :layers in Base.keys(layers) || :connection in Base.keys(layers)
     throw(ArgumentError("a Parallel layer cannot have a named sub-layer called `connection` or `layers`"))
-  elseif isempty(layers)
-    Parallel(connection, ())
   end
+  isempty(layers) && return Parallel(connection, ())
   Parallel(connection, layers)
 end
 
 @functor Parallel
 
-(m::Parallel)(x) = mapreduce(f -> f(x), m.connection, Tuple(m.layers))
-(m::Parallel)(xs...) = mapreduce((f, x) -> f(x), m.connection, Tuple(m.layers), xs)
+(m::Parallel)(x) = m.connection(map(f -> f(x), Tuple(m.layers))...)
 (m::Parallel)(xs::Tuple) = m(xs...)
+function (m::Parallel)(xs...)
+  nl = length(m.layers)
+  nx = length(xs)
+  if nl != nx
+    throw(ArgumentError("Parallel with $nl sub-layers can take one input or $nl inputs, but got $nx inputs"))
+  end
+  m.connection(map(|>, xs, Tuple(m.layers))...)
+end
 
 Base.getindex(m::Parallel, i) = m.layers[i]
-Base.getindex(m::Parallel, i::AbstractVector) = Parallel(m.connection, m.layers[i]...)
+Base.getindex(m::Parallel, i::AbstractVector) = Parallel(m.connection, m.layers[i])
+Base.getindex(m::Parallel{<:Any, <:NamedTuple}, i::AbstractVector) =
+  Parallel(m.connection, NamedTuple{Base.keys(m)[i]}(Tuple(m.layers)[i]))
 
 Base.keys(m::Parallel) = Base.keys(getfield(m, :layers))
 
-trainable(m::Parallel) = (m.connection, m.layers...)
-
 function Base.show(io::IO, m::Parallel)
   print(io, "Parallel(", m.connection, ", ")
   _show_layers(io, m.layers)

src/layers/normalise.jl

@@ -82,8 +82,7 @@ function Dropout(p; dims=:, rng = rng_from_array())
 end
 
 @functor Dropout
-
-trainable(a::Dropout) = ()
+trainable(a::Dropout) = (;)
 
 function (a::Dropout)(x)
   _isactive(a) || return x
@@ -122,8 +121,7 @@ AlphaDropout(p, active) = AlphaDropout(p, active, rng_from_array())
 AlphaDropout(p; rng = rng_from_array()) = AlphaDropout(p, nothing, rng)
 
 @functor AlphaDropout
-
-trainable(a::AlphaDropout) = ()
+trainable(a::AlphaDropout) = (;)
 
 function (a::AlphaDropout)(x::AbstractArray{T}) where T
   _isactive(a) || return x
@@ -301,7 +299,7 @@ function BatchNorm(chs::Int, λ=identity;
 end
 
 @functor BatchNorm
-trainable(bn::BatchNorm) = hasaffine(bn) ? (bn.β, bn.γ) : ()
+trainable(bn::BatchNorm) = hasaffine(bn) ? (β = bn.β, γ = bn.γ) : (;)
 
 function (BN::BatchNorm)(x)
   @assert size(x, ndims(x)-1) == BN.chs
@@ -377,7 +375,7 @@ function InstanceNorm(chs::Int, λ=identity;
 end
 
 @functor InstanceNorm
-trainable(in::InstanceNorm) = hasaffine(in) ? (in.β, in.γ) : ()
+trainable(in::InstanceNorm) = hasaffine(in) ? (β = in.β, γ = in.γ) : (;)
 
 function (l::InstanceNorm)(x)
   @assert ndims(x) > 2
@@ -439,7 +437,7 @@ mutable struct GroupNorm{F,V,N,W}
 end
 
 @functor GroupNorm
-trainable(gn::GroupNorm) = hasaffine(gn) ? (gn.β, gn.γ) : ()
+trainable(gn::GroupNorm) = hasaffine(gn) ? (β = gn.β, γ = gn.γ) : (;)
 
 function GroupNorm(chs::Int, G::Int, λ=identity;
               initβ=zeros32, initγ=ones32,

src/layers/recurrent.jl

@@ -65,7 +65,7 @@ function (m::Recur)(x)
 end
 
 @functor Recur
-trainable(a::Recur) = (a.cell,)
+trainable(a::Recur) = (; cell = a.cell)
 
 Base.show(io::IO, m::Recur) = print(io, "Recur(", m.cell, ")")
 

src/layers/show.jl

@@ -14,7 +14,7 @@ for T in [
 end
 
 function _big_show(io::IO, obj, indent::Int=0, name=nothing)
-  children = trainable(obj)
+  children = _show_children(obj)
   if all(_show_leaflike, children)
     _layer_show(io, obj, indent, name)
   else
@@ -48,6 +48,11 @@ _show_leaflike(::Tuple{Vararg{<:Number}}) = true         # e.g. stride of Conv
 _show_leaflike(::Tuple{Vararg{<:AbstractArray}}) = true  # e.g. parameters of LSTMcell
 _show_leaflike(::Diagonal) = true                        # appears inside LayerNorm
 
+_show_children(x) = trainable(x)  # except for layers which hide their Tuple:
+_show_children(c::Chain) = c.layers
+_show_children(m::Maxout) = m.layers
+_show_children(p::Parallel) = (p.connection, p.layers...)
+
 for T in [
     :Conv, :ConvTranspose, :CrossCor, :DepthwiseConv, :Dense,
     :BatchNorm, :LayerNorm, :InstanceNorm, :GroupNorm,

src/utils.jl

@@ -775,15 +775,20 @@ Chain(
           # plus 2 non-trainable, 128 parameters, summarysize 200.312 KiB.
 
 julia> Flux.modules(m2)
-5-element Vector{Any}:
+7-element Vector{Any}:
  Chain(Chain(Dense(784, 64), BatchNorm(64, relu)), Dense(64, 10))  # 51_018 parameters, plus 128 non-trainable
+ (Chain(Dense(784, 64), BatchNorm(64, relu)), Dense(64, 10))
  Chain(Dense(784, 64), BatchNorm(64, relu))  # 50_368 parameters, plus 128 non-trainable
+ (Dense(784, 64), BatchNorm(64, relu))
  Dense(784, 64)      # 50_240 parameters
  BatchNorm(64, relu)  # 128 parameters, plus 128 non-trainable
  Dense(64, 10)       # 650 parameters
 
 julia> L2(m) = sum(sum(abs2, l.weight) for l in Flux.modules(m) if l isa Dense)
 L2 (generic function with 1 method)
+
+julia> L2(m2) isa Float32
+true
 ```
 """
 modules(m) = [x for x in Functors.fcollect(m) if !isleaflike(x)]

test/layers/basic.jl

@@ -25,6 +25,9 @@ import Flux: activations
     @test m[:first] == m[1]
     @test m[1:2] == m
 
+    @test m == m
+    @test m == fmap(identity, m)  # does not forget names
+
     @test_throws ArgumentError Chain(layers = Dense(10, 10), two = identity) # reserved name
   end
 
@@ -202,14 +205,39 @@ import Flux: activations
       inputs = randn(10), randn(5), randn(4)
       @test size(Parallel(+, Dense(10, 2), Dense(5, 2), Dense(4, 2))(inputs)) == (2,)
       @test size(Parallel(+; a = Dense(10, 2), b = Dense(5, 2), c = Dense(4, 2))(inputs)) == (2,)
+      @test_throws ArgumentError Parallel(+, sin, cos)(1,2,3)  # wrong number of inputs
+      @test Parallel(+, sin, cos)(pi/2) ≈ 1
     end
 
     @testset "named access" begin
       m = Parallel(hcat, one = Dense(10, 10), two = identity)
       @test m[1] == m[:one]
+      @test m[1:2] == m
 
       @test_throws ArgumentError Parallel(hcat, layers = Dense(10, 10), two = identity) # reserved names
       @test_throws ArgumentError Parallel(hcat, connection = Dense(10, 10), two = identity)
+
+      @test m == fmap(identity, m)  # does not forget names
+
+      @test Parallel(vcat, x = log)(1) == [0]
+      @test Parallel(vcat, log)(1) == [0]
+    end
+
+    @testset "trivial cases" begin
+      @test Parallel(hcat) isa Parallel{typeof(hcat), Tuple{}}  # not a NamedTuple
+      @test Parallel(hcat)(1) == hcat()
+      @test Parallel(hcat, inv)(2) == hcat(1/2)  # still calls connection once.
+    end
+
+    @testset "connection is called once" begin
+      CNT = Ref(0)
+      f_cnt = (x...) -> (CNT[]+=1; +(x...))
+      Parallel(f_cnt, sin, cos, tan)(1)
+      @test CNT[] == 1
+      Parallel(f_cnt, sin, cos, tan)(1,2,3)
+      @test CNT[] == 2
+      Parallel(f_cnt, sin)(1)
+      @test CNT[] == 3
     end
 
     # Ref https://github.com/FluxML/Flux.jl/issues/1673

test/runtests.jl

@@ -8,55 +8,58 @@ using CUDA
 
 Random.seed!(0)
 
-@testset "Utils" begin
-  include("utils.jl")
-end
+@testset verbose=true "Flux.jl" begin
 
-@testset "Onehot" begin
-  include("onehot.jl")
-end
+  @testset "Utils" begin
+    include("utils.jl")
+  end
 
-@testset "Optimise" begin
-  include("optimise.jl")
-end
+  @testset "Onehot" begin
+    include("onehot.jl")
+  end
 
-@testset "Data" begin
-  include("data.jl")
-end
+  @testset "Optimise" begin
+    include("optimise.jl")
+  end
 
-@testset "Losses" begin
-  include("losses.jl")
-  include("ctc.jl")
-  CUDA.functional() && include("ctc-gpu.jl")
-end
+  @testset "Data" begin
+    include("data.jl")
+  end
 
-@testset "Layers" begin
-  include("layers/basic.jl")
-  include("layers/normalisation.jl")
-  include("layers/stateless.jl")
-  include("layers/recurrent.jl")
-  include("layers/conv.jl")
-  include("layers/upsample.jl")
-  include("layers/show.jl")
-end
+  @testset "Losses" begin
+    include("losses.jl")
+    include("ctc.jl")
+    CUDA.functional() && include("ctc-gpu.jl")
+  end
 
-@testset "outputsize" begin
-  using Flux: outputsize
-  include("outputsize.jl")
-end
+  @testset "Layers" begin
+    include("layers/basic.jl")
+    include("layers/normalisation.jl")
+    include("layers/stateless.jl")
+    include("layers/recurrent.jl")
+    include("layers/conv.jl")
+    include("layers/upsample.jl")
+    include("layers/show.jl")
+  end
 
-@testset "CUDA" begin
-  if CUDA.functional()
-    include("cuda/runtests.jl")
-  else
-    @warn "CUDA unavailable, not testing GPU support"
+  @testset "outputsize" begin
+    using Flux: outputsize
+    include("outputsize.jl")
+  end
+
+  @testset "CUDA" begin
+    if CUDA.functional()
+      include("cuda/runtests.jl")
+    else
+      @warn "CUDA unavailable, not testing GPU support"
+    end
   end
-end
 
-@static if VERSION == v"1.6"
-  using Documenter
-  @testset "Docs" begin
-    DocMeta.setdocmeta!(Flux, :DocTestSetup, :(using Flux); recursive=true)
-    doctest(Flux)
+  @static if VERSION == v"1.6"
+    using Documenter
+    @testset "Docs" begin
+      DocMeta.setdocmeta!(Flux, :DocTestSetup, :(using Flux); recursive=true)
+      doctest(Flux)
+    end
   end
 end