Skip to content

Specialize lmul!/rmul! for adjoint/transpose #1388

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

Open
wants to merge 3 commits into
base: master
Choose a base branch
from
Open

Specialize lmul!/rmul! for adjoint/transpose #1388

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
d367a85
Specialize lmul!/rmul! for adjoint/transpose
jishnub Jun 19, 2025
a359c7c
Add complex tests
jishnub Jun 19, 2025
a462e5a
Restrict to real/complex numbers
jishnub Jun 21, 2025
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
4 changes: 4 additions & 0 deletions src/adjtrans.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -513,6 +513,10 @@ function _dot_nonrecursive(u, v)
end
end

# we use (n A^T) = (A n)^T, which holds if the product of n and the elements of A is commutative
rmul!(X::AdjOrTrans{<:Union{Real,Complex}}, s::Union{Real,Complex}) = (lmul!(wrapperop(X)(s), parent(X)); X)
lmul!(s::Union{Real,Complex}, X::AdjOrTrans{<:Union{Real,Complex}}) = (rmul!(parent(X), wrapperop(X)(s)); X)
Comment on lines +517 to +518
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I'd suggest to split this and make it available to non-commutative types in the adjoint case.

Suggested change
rmul!(X::AdjOrTrans{<:Union{Real,Complex}}, s::Union{Real,Complex}) = (lmul!(wrapperop(X)(s), parent(X)); X)
lmul!(s::Union{Real,Complex}, X::AdjOrTrans{<:Union{Real,Complex}}) = (rmul!(parent(X), wrapperop(X)(s)); X)
rmul!(X::Transpose{<:Union{Real,Complex}}, s::Union{Real,Complex}) = (lmul!(s, parent(X)); X)
rmul!(X::Adjoint, s::Number) = (lmul!(s', parent(X)); X)
lmul!(s::Union{Real,Complex}, X::Transpose{<:Union{Real,Complex}}) = (rmul!(parent(X), s); X)
lmul!(s::Number, X::Adjoint) = (rmul!(parent(X), s'); X)


# Adjoint/Transpose-vector * vector
*(u::AdjointAbsVec{<:Number}, v::AbstractVector{<:Number}) = dot(u.parent, v)
*(u::TransposeAbsVec{T}, v::AbstractVector{T}) where {T<:Real} = dot(u.parent, v)
Expand Down
28 changes: 28 additions & 0 deletions test/adjtrans.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@ isdefined(Main, :LinearAlgebraTestHelpers) || Base.include(Main, TESTHELPERS)

using Main.LinearAlgebraTestHelpers.OffsetArrays
using Main.LinearAlgebraTestHelpers.ImmutableArrays
using Main.LinearAlgebraTestHelpers.Quaternions

@testset "Adjoint and Transpose inner constructor basics" begin
intvec, intmat = [1, 2], [1 2; 3 4]
Expand Down Expand Up @@ -809,4 +810,31 @@ end
end
end

@testset "lmul!/rmul! by numbers" begin
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Do we have some sort of Quaternions available? We should test this on something that is not commutative, because otherwise the whole left- and right-multiplication difference doesn't become visible.

Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Turns out that this only holds for commutative numbers, so I have restricted this to real and complex numbers. This should cover most use cases.

Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

For the adjoint case, this should work, because we still have (xy)' = y'x'.

@testset "$(eltype(A))" for A in (rand(4, 4), rand(ComplexF64,4,4),
fill([1 2; 3 4], 4, 4),
fill(Quaternion(1,2,3,4), 4, 4))
B = copy(A)
@testset for op in (transpose, adjoint)
A .= B
@test lmul!(2, op(A)) == 2 * op(B)
A .= B
@test rmul!(op(A), 2) == op(B) * 2
if eltype(A) <: Complex
A .= B
@test lmul!(-2im, op(A)) == -2im * op(B)
A .= B
@test rmul!(op(A), -2im) == op(B) * -2im
end
if eltype(A) <: Quaternion
A .= B
q = Quaternion(0,1,4,7)
@test lmul!(q, op(A)) == q * op(B)
A .= B
@test rmul!(op(A), q) == op(B) * q
end
end
end
end

end # module TestAdjointTranspose