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Use new broadcast API #348

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Use new broadcast API #348

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ec78329
first version
pablosanjose Dec 7, 2017
0b7bab8
wip
pablosanjose Dec 7, 2017
1c21255
wip (disabled broadcast!)
pablosanjose Dec 7, 2017
a2995d5
patched broadcast!, added version check
pablosanjose Dec 7, 2017
3ea9ad1
deleted old broadcast.jl
pablosanjose Dec 7, 2017
098dcbb
WIP: trying to fix Scalar broadcast
pablosanjose Dec 7, 2017
48a84b0
Revert "WIP: trying to fix Scalar broadcast"
pablosanjose Dec 7, 2017
d6b58f4
Whitespace
pablosanjose Dec 7, 2017
1a00c3f
Reverted use of uninitialised for compatibility
pablosanjose Dec 7, 2017
75dc71e
fix Scalar broadcast, array precedence
pablosanjose Dec 7, 2017
2edd21e
Less binary BroadcastStyle methods
pablosanjose Dec 7, 2017
b146f8a
Avoid calling dynamic combine_indices (duh!)
pablosanjose Dec 7, 2017
5d5bab6
Addressed points by andyferris
pablosanjose Dec 8, 2017
b70fae3
add a DefaultArrayStyle rule
pablosanjose Dec 10, 2017
d7b23dd
edited comments, added reminders to fix VectorStyle, MatrixStyle
pablosanjose Dec 10, 2017
35969d7
Adapt to new broadcast! implementation in Base.
tkoolen Jan 10, 2018
0ccfc43
Merge pull request #1 from tkoolen/tk/newbroadcast
pablosanjose Jan 15, 2018
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111 changes: 72 additions & 39 deletions src/broadcast.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -2,37 +2,77 @@
## broadcast! ##
################

import Base.Broadcast:
if VERSION < v"0.7.0-DEV.2638"
## Old Broadcast API ##
import Base.Broadcast:
_containertype, promote_containertype, broadcast_indices,
broadcast_c, broadcast_c!

# Add StaticArray as a new output type in Base.Broadcast promotion machinery.
# This isn't the precise output type, just a placeholder to return from
# promote_containertype, which will control dispatch to our broadcast_c.
_containertype(::Type{<:StaticArray}) = StaticArray
_containertype(::Type{<:RowVector{<:Any,<:SVector}}) = StaticArray

# With the above, the default promote_containertype gives reasonable defaults:
# StaticArray, StaticArray -> StaticArray
# Array, StaticArray -> Array
#
# We could be more precise about the latter, but this isn't really possible
# without using Array{N} rather than Array in Base's promote_containertype.
#
# Base also has broadcast with tuple + Array, but while implementing this would
# be consistent with Base, it's not exactly clear it's a good idea when you can
# just use an SVector instead?
promote_containertype(::Type{StaticArray}, ::Type{Any}) = StaticArray
promote_containertype(::Type{Any}, ::Type{StaticArray}) = StaticArray

broadcast_indices(::Type{StaticArray}, A) = indices(A)


# Override for when output type is deduced to be a StaticArray.
@inline function broadcast_c(f, ::Type{StaticArray}, as...)
_broadcast(f, broadcast_sizes(as...), as...)
# Add StaticArray as a new output type in Base.Broadcast promotion machinery.
# This isn't the precise output type, just a placeholder to return from
# promote_containertype, which will control dispatch to our broadcast_c.
_containertype(::Type{<:StaticArray}) = StaticArray
_containertype(::Type{<:RowVector{<:Any,<:SVector}}) = StaticArray

# With the above, the default promote_containertype gives reasonable defaults:
# StaticArray, StaticArray -> StaticArray
# Array, StaticArray -> Array
#
# We could be more precise about the latter, but this isn't really possible
# without using Array{N} rather than Array in Base's promote_containertype.
#
# Base also has broadcast with tuple + Array, but while implementing this would
# be consistent with Base, it's not exactly clear it's a good idea when you can
# just use an SVector instead?
promote_containertype(::Type{StaticArray}, ::Type{Any}) = StaticArray
promote_containertype(::Type{Any}, ::Type{StaticArray}) = StaticArray

# Override for when output type is deduced to be a StaticArray.
@inline function broadcast_c(f, ::Type{StaticArray}, as...)
_broadcast(f, broadcast_sizes(as...), as...)
end

# TODO: This signature could be relaxed to (::Any, ::Type{StaticArray}, ::Type, ...), though
# we'd need to rework how _broadcast!() and broadcast_sizes() interact with normal AbstractArray.
@inline function broadcast_c!(f, ::Type{StaticArray}, ::Type{StaticArray}, dest, as...)
_broadcast!(f, Size(dest), dest, broadcast_sizes(as...), as...)
end
else
## New Broadcast API ##
import Base.Broadcast:
BroadcastStyle, AbstractArrayStyle, broadcast

# Add a new BroadcastStyle for StaticArrays, derived from AbstractArrayStyle
# A constructor that changes the style parameter N (array dimension) is also required
struct StaticArrayStyle{N} <: AbstractArrayStyle{N} end
StaticArrayStyle{M}(::Val{N}) where {M,N} = StaticArrayStyle{N}()

BroadcastStyle(::Type{<:StaticArray{D, T, N}}) where {D, T, N} = StaticArrayStyle{N}()

# Fix Precedence: Make StaticArray - Array -> Array
BroadcastStyle(::StaticArrayStyle{M}, ::Broadcast.VectorStyle) where M = Broadcast.Unknown()
BroadcastStyle(::StaticArrayStyle{M}, ::Broadcast.MatrixStyle) where M = Broadcast.Unknown()
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VectorStyle and MatrixStyle are unfortunate (and hopefully temporary) objects because we don't trust that sparse broadcasting generalizes correctly beyond Array (see JuliaLang/julia#23939 (comment)). However, this suggests we'll have to support them throughout julia 1.x. 😢

Long-term the one we want to implement would be with DefaultArrayStyle. Instead of returning Unknown, it might be best to do something like this (untested):

BroadcastStyle(::StaticArrayStyle{M}, ::Broadcast.DefaultArrayStyle{N}) where {M,N} =
    DefaultArrayStyle(Broadcast._max(Val(M), Val(N))

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Hey Tim, thanks for reviewing! Your designs are a pleasure to work with.

So you suggest including this rule, in addition to the VectorStyle and MatrixStyle ones, to take over once the latter are removed, yes? Done.

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Right. Also the DefaultArrayStyle is necessary even now for dimensions higher than 2.

Thanks for the kind words about the API. I think it's also fair to say that unfortunately they don't help StaticArrays that much; they're more oriented around improving the API for mutable arrays. But at least it's documented, and hopefully that's worth something.

Really grateful to you for tackling this!


# Add a broadcast method that calls the @generated routine
@inline function broadcast(f, ::StaticArrayStyle, ::Void, ::Void, As...)
_broadcast(f, broadcast_sizes(As...), As...)
end

# Add a specialized broadcast! method that overrides the Base fallback and calls the old routine
# TODO: This signature could be relaxed to (::AbstractArray, ::Vararg{StaticArray,N}), ::Type, ...), though
# we'd need to rework how _broadcast!() and broadcast_sizes() interact with normal AbstractArray.
@inline function broadcast!(f, C::StaticArray, As::Vararg{StaticArray,N}) where {N}
_broadcast!(f, Size(C), C, broadcast_sizes(As...), As...)
end
end


##############################################
## Old broadcast machinery for StaticArrays ##
##############################################

broadcast_indices(A::StaticArray) = indices(A)

@inline broadcast_sizes(a::RowVector{<:Any,<:SVector}, as...) = (Size(a), broadcast_sizes(as...)...)
@inline broadcast_sizes(a::StaticArray, as...) = (Size(a), broadcast_sizes(as...)...)
@inline broadcast_sizes(a, as...) = (Size(), broadcast_sizes(as...)...)
Expand Down Expand Up @@ -113,21 +153,14 @@ end

if VERSION < v"0.7.0-DEV"
# Workaround for #329
@inline function Base.broadcast(f, ::Type{T}, a::StaticArray) where {T}
map(x->f(T,x), a)
end
end

################
## broadcast! ##
################

# TODO: This signature could be relaxed to (::Any, ::Type{StaticArray}, ::Type, ...), though
# we'd need to rework how _broadcast!() and broadcast_sizes() interact with normal AbstractArray.
@inline function broadcast_c!(f, ::Type{StaticArray}, ::Type{StaticArray}, dest, as...)
_broadcast!(f, Size(dest), dest, broadcast_sizes(as...), as...)
@inline function Base.broadcast(f, ::Type{T}, a::StaticArray) where {T}
map(x->f(T,x), a)
end
end

###############################################
## Old broadcast! machinery for StaticArrays ##
###############################################

@generated function _broadcast!(f, ::Size{newsize}, dest::StaticArray, s::Tuple{Vararg{Size}}, as...) where {newsize}
sizes = [sz.parameters[1] for sz ∈ s.parameters]
Expand Down