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Disable + and - rules on mixed numeric types #787

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Disable + and - rules on mixed numeric types
oxinabox Mar 1, 2024
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oxinabox Mar 1, 2024
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oxinabox Mar 1, 2024
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58 changes: 50 additions & 8 deletions src/rulesets/Base/fastmath_able.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -164,19 +164,61 @@ let
return (Ω, hypot_pullback)
end

@scalar_rule x + y (true, true)
@scalar_rule x - y (true, -1)
@scalar_rule x / y (one(x) / y, -(Ω / y))

## many-arg +
function frule(Δs, ::typeof(+), x::Number, ys::Number...)
###
### +
###
# Same type so must have same tangent type
function frule(Δs, ::typeof(+), x::T, ys::T...) where {T<:Number}
+(x, ys...), +(Base.tail(Δs)...)
end

function rrule(::typeof(+), x::Number, ys::Number...)
function rrule(::typeof(+), x::T, ys::T...) where {T<:Number}
plus_back(dz) = (NoTangent(), dz, map(Returns(dz), ys)...)
+(x, ys...), plus_back
end
end

#Or Tangent type is same as primal type so op must be defined on it too
function frule(
(_, ẋ, ẏ)::Tuple{<:Any,A,B}, ::typeof(+), x::A, y::B
) where {A<:Number,B<:Number}
return +(x, y), +(ẋ, ẏ)
end

# Both cases (break ambiguity)
function frule(
(_, ẋ, ẏ)::Tuple{<:Any,T,T}, ::typeof(+), x::T, y::T
) where {T<:Number}
return +(x, y), +(ẋ, ẏ)
end

###
### -
###
# Same type so must have same tangent type
function rrule(::typeof(-), x::T, y::T) where {T<:Number}
minus_pullback(z̄) = NoTangent(), z̄, -(z̄)
return x - y, minus_pullback
end
function frule((_, ẋ, ẏ), ::typeof(-), x::T, y::T) where {T<:Number}
return -(x, y), -(ẋ, ẏ)
end

#Or Tangent type is same as primal type so op must be defined on it too
function frule(
(_, ẋ, ẏ)::Tuple{<:Any,A,B}, ::typeof(-), x::A, y::B
) where {A<:Number,B<:Number}
return -(x, y), -(ẋ, ẏ)
end

# Both cases (break ambiguity)
function frule(
(_, ẋ, ẏ)::Tuple{<:Any,T,T}, ::typeof(-), x::T, y::T
) where {T<:Number}
return -(x, y), -(ẋ, ẏ)
end

@scalar_rule x / y (one(x) / y, -(Ω / y))


## power
# literal_pow is in base.jl
Expand Down
31 changes: 27 additions & 4 deletions test/rulesets/Base/fastmath_able.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -144,17 +144,17 @@ const FASTABLE_AST = quote
@assert T == typeof(f(x, y))
Δz = randn(typeof(f(x, y)))

@test frule((ZeroTangent(), Δx, Δy), f, x, y) isa Tuple{T, T}
@test frule((NoTangent(), Δx, Δy), f, x, y) isa Tuple{T,T}
_, ∂x, ∂y = rrule(f, x, y)[2](Δz)
@test (∂x, ∂y) isa Tuple{T, T}

if f != hypot
if f ∉ (hypot, +, -)
# Issue #233
@test frule((ZeroTangent(), Δx, Δy), f, x, 2) isa Tuple{T, T}
@test frule((NoTangent(), Δx, Δy), f, x, 2) isa Tuple{T,T}
_, ∂x, ∂y = rrule(f, x, 2)[2](Δz)
@test (∂x, ∂y) isa Tuple{T, Float64}

@test frule((ZeroTangent(), Δx, Δy), f, 2, y) isa Tuple{T, T}
@test frule((NoTangent(), Δx, Δy), f, 2, y) isa Tuple{T,T}
_, ∂x, ∂y = rrule(f, 2, y)[2](Δz)
@test (∂x, ∂y) isa Tuple{Float64, T}
end
Expand Down Expand Up @@ -283,6 +283,29 @@ const FASTABLE_AST = quote
end
end
end

@testset "+,- on weird types" begin
struct StoreHalfed <: Number
val::Float64
StoreHalfed(x) = new(x / 2)
end
Base.:-(x::StoreHalfed, y::Number) = 2 * x.val - y
Base.:+(x::StoreHalfed, y::Number) = 2 * x.val + y

sh1 = StoreHalfed(4.0)
sh2 = StoreHalfed(8.0)
f1 = 40.0
f2 = 80.0

# We have had issues with mixed number types before
# So these should not hit
@test rrule(+, sh1, f1) == nothing
@test rrule(-, sh1, f1) == nothing
@test frule((NoTangent(), Tangent{StoreHalfed}(; val=2.0), 20.0), +, sh1, f1) ==
nothing
@test frule((NoTangent(), Tangent{StoreHalfed}(; val=2.0), 20.0), -, sh1, f1) ==
nothing
end
end

# Now we generate tests for fast and nonfast versions
Expand Down