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Project ZeroTangent to natural tangent for some number types #574

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Project ZeroTangent to natural tangent for some number types #574

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81736ce
project ZeroTangent to natural tangent for some number types
ToucheSir Aug 10, 2022
54fcbed
Tweak tests to match wrt. natural tangents
ToucheSir Aug 10, 2022
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1 change: 1 addition & 0 deletions src/projection.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -191,6 +191,7 @@ end
# understands, including a mix of Zeros & reals. Other cases, we just let through:
(project::ProjectTo{<:Number})(dx::Tangent{<:Complex}) = project(Complex(dx.re, dx.im))
(::ProjectTo{<:Number})(dx::Tangent{<:Number}) = dx
(::ProjectTo{T})(::ZeroTangent) where {T<:Real} = zero(T)

# Arrays
# If we don't have a more specialized `ProjectTo` rule, we just assume that there is
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11 changes: 5 additions & 6 deletions test/projection.jl
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Expand Up @@ -37,10 +37,10 @@ struct NoSuperType end
@test ProjectTo(1.0)(2) === 2.0

# Tangents
ProjectTo(1.0f0 + 2im)(Tangent{ComplexF64}(; re=1, im=NoTangent())) ===
1.0f0 + 0.0f0im

@test 1.0 === ProjectTo(1.0)(Tangent{ComplexF64}(; re=1, im=NoTangent()))
complex_tangent = Tangent{ComplexF64}(; re=1, im=NoTangent())
@test ProjectTo(1.0f0 + 2im)(complex_tangent) === 1.0f0 + 0.0f0im
@test ProjectTo(1.0)(complex_tangent) === 1.0
Comment on lines +40 to +42
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unreleated fix?

@test ProjectTo(1.0)(ZeroTangent()) === 0.0
end

@testset "Dual" begin # some weird Real subtype that we should basically leave alone
Expand Down Expand Up @@ -212,7 +212,7 @@ struct NoSuperType end
@test ProjectTo(I)(123) === NoTangent()
@test ProjectTo(2 * I)(I * 3im) === 0.0 * I
@test ProjectTo((4 + 5im) * I)(Tangent{typeof(im * I)}(; λ = 6)) === (6.0 + 0.0im) * I
@test ProjectTo(7 * I)(Tangent{typeof(2I)}()) == ZeroTangent()
@test ProjectTo(7 * I)(Tangent{typeof(2I)}()) == 0.0I
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hmm not sure that this is a good thing.
Does this also happen to other matrix types?

end

@testset "LinearAlgebra: $adj vectors" for adj in [transpose, adjoint]
Expand Down Expand Up @@ -413,7 +413,6 @@ struct NoSuperType end
@test pb(ZeroTangent()) isa AbstractZero # was a method ambiguity!

# all projectors preserve Zero, and specific type, via one fallback method:
@test ProjectTo(pi)(ZeroTangent()) === ZeroTangent()
@test ProjectTo(pi)(NoTangent()) === NoTangent()
pv = ProjectTo(sprand(30, 0.3))
@test pv(ZeroTangent()) === ZeroTangent()
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2 changes: 1 addition & 1 deletion test/rules.jl
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Expand Up @@ -94,7 +94,7 @@ _second(t) = Base.tuple_type_head(Base.tuple_type_tail(t))
frx, nice_pushforward = frule((dself, 1), nice, 1)
@test nice_pushforward === ZeroTangent()
rrx, nice_pullback = rrule(nice, 1)
@test (NoTangent(), ZeroTangent()) === nice_pullback(1)
@test (NoTangent(), 0.0) === nice_pullback(1)

# Test that these run. Do not care about numerical correctness.
@test frule((nothing, 1.0, 1.0, 1.0), varargs_function, 0.5, 0.5, 0.5) == (1.5, 3.0)
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