Skip to content

Fix rrule for broadcasted over empty Tuple{} #834

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
ChrisRackauckas merged 4 commits into from
Feb 11, 2026
+15 −1
Merged

Fix rrule for broadcasted over empty Tuple{} #834

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
99f9abe
Fix rrule for broadcasted over empty Tuple{}
ChrisRackauckas Feb 11, 2026
3e5b9c4
Update test/rulesets/Base/broadcast.jl
ChrisRackauckas Feb 11, 2026
5b5d269
Update test/rulesets/Base/broadcast.jl
ChrisRackauckas Feb 11, 2026
4069462
Add multi-argument test for broadcast over empty tuples
ChrisRackauckas Feb 11, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion src/rulesets/Base/broadcast.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -28,7 +28,7 @@ end

function rrule(cfg::RCR, ::typeof(broadcasted), ::BroadcastStyle, f::F, args::Vararg{Any,N}) where {F,N}
T = Broadcast.combine_eltypes(f, args)
if T === Bool # TODO use nondifftype here
if T === Bool || T === Union{} # TODO use nondifftype here
# 1: Trivial case: non-differentiable output, e.g. `x .> 0`
@debug("split broadcasting trivial", f, T)
bc_trivial_back(_) = (TRI_NO..., ntuple(Returns(ZeroTangent()), length(args))...)
Expand Down
14 changes: 14 additions & 0 deletions test/rulesets/Base/broadcast.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -177,6 +177,20 @@ BT1 = Broadcast.BroadcastStyle(Tuple)
end

@testset "bugs" begin
@testset "broadcast over empty tuple" begin # https://github.com/JuliaDiff/ChainRules.jl/issues/830
y, bk = rrule(CFG, copy∘broadcasted, BT1, isone, ())
@test y == ()
@test bk(Tangent{Tuple{}}()) == (NoTangent(), NoTangent(), NoTangent(), ZeroTangent())

y2, bk2 = rrule(CFG, copy∘broadcasted, BT1, sin, ())
@test y2 == ()
@test bk2(Tangent{Tuple{}}()) == (NoTangent(), NoTangent(), NoTangent(), ZeroTangent())

# Multi-argument case
y3, bk3 = rrule(CFG, copy∘broadcasted, BT1, atan, (), ())
@test y3 == ()
@test bk3(Tangent{Tuple{}}()) == (NoTangent(), NoTangent(), NoTangent(), ZeroTangent(), ZeroTangent())
end
@testset "unbroadcast with NTuple" begin # https://github.com/JuliaDiff/ChainRules.jl/pull/661
@test ChainRules.unbroadcast((1, 2, [3]), [4, 5, [6]]) isa Tangent # earlier, NTuple demanded same type
@test ChainRules.unbroadcast(broadcasted(-, (1, 2), 3), (4, 5)) == (4, 5) # earlier, called ndims(::Tuple)
Expand Down
Loading