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RFC: better ntuple implementation without @generated #13439

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RFC: better ntuple implementation without @generated #13439

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2 changes: 1 addition & 1 deletion base/coreimg.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -29,9 +29,9 @@ include("options.jl")
typealias Cint Int32
typealias Csize_t UInt
include("promotion.jl")
include("expr.jl")
include("tuple.jl")
include("range.jl")
include("expr.jl")
include("error.jl")

# core numeric operations & types
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4 changes: 1 addition & 3 deletions base/deprecated.jl
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Expand Up @@ -403,8 +403,6 @@ end

@deprecate with_env(f::Function, key::AbstractString, val) withenv(f, key=>val)

@deprecate ntuple(n::Integer, f::Function) ntuple(f, n)

# 0.4 discontinued functions

@noinline function subtypetree(x::DataType, level=-1)
Expand Down Expand Up @@ -841,4 +839,4 @@ for f in (:remotecall, :remotecall_fetch, :remotecall_wait)
@deprecate ($f)(w::Worker, f::Function, args...) ($f)(f, w::Worker, args...)
@deprecate ($f)(id::Integer, f::Function, args...) ($f)(f, id::Integer, args...)
end
end
end
3 changes: 3 additions & 0 deletions base/inference.jl
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Expand Up @@ -458,6 +458,9 @@ const apply_type_tfunc = function (A, args...)
end
add_tfunc(apply_type, 1, IInf, apply_type_tfunc)

## external tfunc additions ##
add_tfunc(ntuple, 2, 2, _ntuple_tfunc)

function tuple_tfunc(argtype::ANY)
if isa(argtype,DataType) && argtype.name === Tuple.name
p = map(x->(isType(x) && !isa(x.parameters[1],TypeVar) ? typeof(x.parameters[1]) : x),
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2 changes: 1 addition & 1 deletion base/sysimg.jl
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Expand Up @@ -35,9 +35,9 @@ include("options.jl")

# core operations & types
include("promotion.jl")
include("expr.jl")
include("tuple.jl")
include("range.jl")
include("expr.jl")
include("error.jl")

# core numeric operations & types
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46 changes: 30 additions & 16 deletions base/tuple.jl
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Expand Up @@ -29,29 +29,43 @@ eltype{T,_}(::Type{NTuple{_,T}}) = T

## mapping ##

ntuple(f::Function, n::Integer) =
const ntuple = function(f, n::Integer)
n<=0 ? () :
n==1 ? (f(1),) :
n==2 ? (f(1),f(2),) :
n==3 ? (f(1),f(2),f(3),) :
n==4 ? (f(1),f(2),f(3),f(4),) :
n==5 ? (f(1),f(2),f(3),f(4),f(5),) :
tuple(ntuple(f,n-5)..., f(n-4), f(n-3), f(n-2), f(n-1), f(n))

ntuple(f, ::Type{Val{0}}) = ()
ntuple(f, ::Type{Val{1}}) = (f(1),)
ntuple(f, ::Type{Val{2}}) = (f(1),f(2))
ntuple(f, ::Type{Val{3}}) = (f(1),f(2),f(3))
ntuple(f, ::Type{Val{4}}) = (f(1),f(2),f(3),f(4))
ntuple(f, ::Type{Val{5}}) = (f(1),f(2),f(3),f(4),f(5))
@generated function ntuple{N}(f, ::Type{Val{N}})
if !isa(N,Int)
:(throw(TypeError(:ntuple, "", Int, $(QuoteNode(N)))))
tuple([f(i) for i = 1:Int(n)]...)
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Would be awesome if we didn't have that splatting penalty...

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if ntuple doesn't get inlined (say, because there are too many cases or f is unknown), the cost of splatting is the easy part. ideally, this will eventually be accessible as a direct iterator: (f(i) for i = 1:Int(n))

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From the compiler standpoint it may be the easy part, but it's the one part that you can't do anything about from the Julia side short of writing a @generated function. (Inlining can be forced with @inline, f could be defined as a Functor.) I expect you noticed #13359. We're talking factors of 100 in terms of performance.

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i haven't looked into the exact issues in #13359 to see which point in codegen is pessimizing its assumptions for that example. but this is calling tuple, which is a more like syntax than an actual function call. the tfunc below then tries to do a better job of computing the type information that will be needed by the callee to limit the loss of type information in the caller where it could cause a much greater slowdown.

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Sounds like a big step in the right direction, then.

end

const _ntuple_tfunc_gensym = gensym()
const _ntuple_tfunc = function(argtypes, argexprs, vtypes, sv)
n = false
if isa(argexprs[2], Integer)
try
n = Int(argexprs[2])
end
end

Core.Inference.setindex!(vtypes,
Core.Inference.call(Core.Inference.VarState, Int, false),
_ntuple_tfunc_gensym)
F = Core.Inference.abstract_eval_call(
Expr(:call, argexprs[1], _ntuple_tfunc_gensym),
vtypes, sv)
Core.Inference.delete!(vtypes,
_ntuple_tfunc_gensym)

if isa(n, Int)
return NTuple{n, F}
elseif F === Any
return Tuple
else
M = N-5
:(tuple(ntuple(f, Val{$M})..., f($N-4), f($N-3), f($N-2), f($N-1), f($N)))
return Tuple{Vararg{F}}
end
end
if isdefined(Core, :Inference) && isdefined(Core.Inference, :add_tfunc)
Core.Inference.add_tfunc(ntuple, 2, 2, _ntuple_tfunc)
end
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Does all this have to go here rather than in inference.jl?

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yes, that's part of the strategy here. there are two ntuple functions (Core.Inference and Base), and inference needs to know about both.


# 0 argument function
map(f) = f()
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16 changes: 9 additions & 7 deletions test/tuple.jl
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Expand Up @@ -145,12 +145,14 @@ foo(x, y, z) = x + y + z
@test any((true,true,false)) === true
@test any((true,true,true)) === true

@test @inferred(ntuple(Base.Abs2Fun(), Val{0})) == ()
@test @inferred(ntuple(Base.Abs2Fun(), Val{2})) == (1, 4)
@test @inferred(ntuple(Base.Abs2Fun(), Val{3})) == (1, 4, 9)
@test @inferred(ntuple(Base.Abs2Fun(), Val{4})) == (1, 4, 9, 16)
@test @inferred(ntuple(Base.Abs2Fun(), Val{5})) == (1, 4, 9, 16, 25)
@test @inferred(ntuple(Base.Abs2Fun(), Val{6})) == (1, 4, 9, 16, 25, 36)
ntuple_val{T}(x, ::Type{Val{T}}) = ntuple(x, T)
@test @inferred(ntuple_val(Base.Abs2Fun(), Val{0})) == ()
@test @inferred(ntuple_val(Base.Abs2Fun(), Val{2})) == (1, 4)
@test @inferred(ntuple_val(Base.Abs2Fun(), Val{3})) == (1, 4, 9)
@test @inferred(ntuple_val(Base.Abs2Fun(), Val{4})) == (1, 4, 9, 16)
@test @inferred(ntuple_val(Base.Abs2Fun(), Val{5})) == (1, 4, 9, 16, 25)
@test @inferred(ntuple_val(Base.Abs2Fun(), Val{6})) == (1, 4, 9, 16, 25, 36)

# issue #12854
@test_throws TypeError ntuple(identity, Val{1:2})
@test_throws TypeError ntuple(identity, Val{1})
@test_throws TypeError ntuple_val(identity, Val{1:2})