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Destination zeros from eltype in zero-length generic_matvecmul #1241

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Merged
merged 3 commits into from
Apr 1, 2025
Merged

Destination zeros from eltype in zero-length generic_matvecmul #1241

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720327b
Destination zeros from eltype in zero-length generic_matvecmul
jishnub Mar 16, 2025
388fe10
Fix test
jishnub Mar 16, 2025
451f015
Use eltype in adjoint matvec
jishnub Mar 17, 2025
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4 changes: 2 additions & 2 deletions src/matmul.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -932,7 +932,7 @@ function __generic_matvecmul!(f::F, C::AbstractVector, A::AbstractVecOrMat, B::A
@inbounds begin
if length(B) == 0
for k = eachindex(C)
@stable_muladdmul _modify!(MulAddMul(alpha,beta), false, C, k)
@stable_muladdmul _modify!(MulAddMul(alpha,beta), zero(eltype(C)), C, k)
end
else
for k = eachindex(C)
Expand All @@ -955,7 +955,7 @@ function __generic_matvecmul!(::typeof(identity), C::AbstractVector, A::Abstract
if !iszero(beta)
C[i] *= beta
elseif length(B) == 0
C[i] = false
C[i] = zero(eltype(C))
else
C[i] = zero(A[i]*B[1] + A[i]*B[1])
end
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17 changes: 17 additions & 0 deletions test/matmul.jl
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Expand Up @@ -6,6 +6,11 @@ using Base: rtoldefault
using Test, LinearAlgebra, Random
using LinearAlgebra: mul!, Symmetric, Hermitian

const BASE_TEST_PATH = joinpath(Sys.BINDIR, "..", "share", "julia", "test")

isdefined(Main, :SizedArrays) || @eval Main include(joinpath($(BASE_TEST_PATH), "testhelpers", "SizedArrays.jl"))
using .Main.SizedArrays

## Test Julia fallbacks to BLAS routines

mul_wrappers = [
Expand Down Expand Up @@ -1176,4 +1181,16 @@ end
end
end

@testset "zero-length generic matvec" begin
m = SizedArrays.SizedArray{(2,2)}(ones(2,2))
A = fill(m, 2, 0)
v = fill(m, size(A,2))
w = similar(v, size(A,1))
mul!(w, A, v)
@test all(iszero, w)
A = fill(m, 0, 2)
mul!(w, A', v)
@test all(iszero, w)
end

end # module TestMatmul