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Fix seeding with undefined elements #743

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Merged
merged 4 commits into from
Aug 25, 2025
Merged

Fix seeding with undefined elements #743

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009dce8
Fix seeding with undefined elements
devmotion Apr 7, 2025
6f8f6a9
Merge branch 'master' into dw/seed_non_bitstypes
devmotion Aug 25, 2025
ec3e483
Extend tests to cover all branches
devmotion Aug 25, 2025
0fe9797
Bump version to 1.0.2
devmotion Aug 25, 2025
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2 changes: 1 addition & 1 deletion Project.toml
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
name = "ForwardDiff"
uuid = "f6369f11-7733-5829-9624-2563aa707210"
version = "1.0.1"
version = "1.0.2"

[deps]
CommonSubexpressions = "bbf7d656-a473-5ed7-a52c-81e309532950"
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56 changes: 48 additions & 8 deletions src/apiutils.jl
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Expand Up @@ -72,16 +72,36 @@ end

function seed!(duals::AbstractArray{Dual{T,V,N}}, x,
seed::Partials{N,V} = zero(Partials{N,V})) where {T,V,N}
for idx in structural_eachindex(duals, x)
duals[idx] = Dual{T,V,N}(x[idx], seed)
if isbitstype(V)
for idx in structural_eachindex(duals, x)
duals[idx] = Dual{T,V,N}(x[idx], seed)
end
else
for idx in structural_eachindex(duals, x)
if isassigned(x, idx)
duals[idx] = Dual{T,V,N}(x[idx], seed)
else
Base._unsetindex!(duals, idx)
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@KristofferC KristofferC Apr 8, 2025

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:/, this is quite unfortunate, is this really the only way to fix this?

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@gdalle gdalle Apr 8, 2025

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I think the idea is that if x[idx] is #undef, we want duals[idx] to be the same

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@devmotion devmotion Apr 8, 2025

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Yeah, I wasn't 100% percent happy but it was the best I could think of and what apparently is used in base. IMO we really want to ensure here that we get the same behaviour as copyto! on the primal part, to avoid that yduals contains any surprising values, possibly from previous chunks or differentations.

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@devmotion devmotion Apr 8, 2025

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julia> x = BigFloat[1, 2];

julia> y = similar(x); y[2] = 1;

julia> x
2-element Vector{BigFloat}:
 1.0
 2.0

julia> y
2-element Vector{BigFloat}:
 #undef
   1.0

julia> copyto!(x, y);

julia> x
2-element Vector{BigFloat}:
 #undef
   1.0

end
end
end
return duals
end

function seed!(duals::AbstractArray{Dual{T,V,N}}, x,
seeds::NTuple{N,Partials{N,V}}) where {T,V,N}
for (i, idx) in zip(1:N, structural_eachindex(duals, x))
duals[idx] = Dual{T,V,N}(x[idx], seeds[i])
if isbitstype(V)
for (i, idx) in zip(1:N, structural_eachindex(duals, x))
duals[idx] = Dual{T,V,N}(x[idx], seeds[i])
end
else
for (i, idx) in zip(1:N, structural_eachindex(duals, x))
if isassigned(x, idx)
duals[idx] = Dual{T,V,N}(x[idx], seeds[i])
else
Base._unsetindex!(duals, idx)
end
end
end
return duals
end
Expand All @@ -90,8 +110,18 @@ function seed!(duals::AbstractArray{Dual{T,V,N}}, x, index,
seed::Partials{N,V} = zero(Partials{N,V})) where {T,V,N}
offset = index - 1
idxs = Iterators.drop(structural_eachindex(duals, x), offset)
for idx in idxs
duals[idx] = Dual{T,V,N}(x[idx], seed)
if isbitstype(V)
for idx in idxs
duals[idx] = Dual{T,V,N}(x[idx], seed)
end
else
for idx in idxs
if isassigned(x, idx)
duals[idx] = Dual{T,V,N}(x[idx], seed)
else
Base._unsetindex!(duals, idx)
end
end
end
return duals
end
Expand All @@ -100,8 +130,18 @@ function seed!(duals::AbstractArray{Dual{T,V,N}}, x, index,
seeds::NTuple{N,Partials{N,V}}, chunksize = N) where {T,V,N}
offset = index - 1
idxs = Iterators.drop(structural_eachindex(duals, x), offset)
for (i, idx) in zip(1:chunksize, idxs)
duals[idx] = Dual{T,V,N}(x[idx], seeds[i])
if isbitstype(V)
for (i, idx) in zip(1:chunksize, idxs)
duals[idx] = Dual{T,V,N}(x[idx], seeds[i])
end
else
for (i, idx) in zip(1:chunksize, idxs)
if isassigned(x, idx)
duals[idx] = Dual{T,V,N}(x[idx], seeds[i])
else
Base._unsetindex!(duals, idx)
end
end
end
return duals
end
29 changes: 29 additions & 0 deletions test/JacobianTest.jl
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Expand Up @@ -279,4 +279,33 @@ end
end
end

# issues #436, #740
@testset "BigFloat" begin
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@gdalle gdalle Apr 8, 2025

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Does this test cover all the new branches? It seems CodeCov is sleeping at the wheel.
I think we may also want to add cases where only some of the values are uninitialized?

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@devmotion devmotion Aug 25, 2025 •
edited
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Codecov results are available on the codecov webpage: https://app.codecov.io/github/JuliaDiff/ForwardDiff.jl/commit/6f8f6a977d4d69fda7c492f6e0a47cb8a6853045 (I assume the codecov app is not installed in the repo and hence there's no nice summary in the PR - AFAICT I don't have sufficient permissions to install it)

Indeed, you were right, the tests did not cover all new branches. I extended the tests, and locally it seems that they cover all branches as commenting out any of the branches leads to test failures.

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@devmotion devmotion Aug 25, 2025

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Codecov confirms that all modified lines are covered by the tests: https://app.codecov.io/github/JuliaDiff/ForwardDiff.jl/commit/ec3e483747159b46e0db5328c60c3543c13478a6/indirect-changes

# Unassigned entries in the output
x = BigFloat.(1:9)
for chunksize in (1, 2, 9)
y = similar(x)
@test all(i -> !isassigned(y, i), eachindex(y))
cfg = ForwardDiff.JacobianConfig(copyto!, y, x, ForwardDiff.Chunk{chunksize}())
res = ForwardDiff.jacobian(copyto!, y, x, cfg)
@test y == x
@test res isa Matrix{BigFloat}
@test res == I
end

# Unassigned (but unused) entry in the input and unassigned entries in the output
resize!(x, 10)
f = (y, x) -> copyto!(y, 1, x, 1, 9)
for chunksize in (1, 2, 10)
y = similar(x, 9)
@test all(i -> !isassigned(y, i), eachindex(y))
cfg = ForwardDiff.JacobianConfig(f, y, x, ForwardDiff.Chunk{chunksize}())
res = ForwardDiff.jacobian(f, y, x, cfg)
@test y == x[1:(end-1)]
@test res isa Matrix{BigFloat}
@test res[:, 1:(end-1)] == I
@test all(iszero, res[:, end])
end
end

end # module
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