Tests for in-place kron (#36488)

Co-authored-by: Daniel Karrasch <Daniel.Karrasch@gmx.de>
JuliaLang · Jul 3, 2020 · 66f41c5 · 66f41c5 · nanosoldier · Jul 3, 2020
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diff --git a/stdlib/LinearAlgebra/src/dense.jl b/stdlib/LinearAlgebra/src/dense.jl
@@ -413,6 +413,7 @@ function kron(a::AbstractMatrix{T}, b::AbstractMatrix{S}) where {T,S}
 end
 
 kron!(c::AbstractVecOrMat, a::AbstractVecOrMat, b::Number) = mul!(c, a, b)
+kron!(c::AbstractVecOrMat, a::Number, b::AbstractVecOrMat) = mul!(c, a, b)
 
 Base.@propagate_inbounds function kron!(c::AbstractVector, a::AbstractVector, b::AbstractVector)
     C = reshape(c, length(a)*length(b), 1)

diff --git a/stdlib/LinearAlgebra/test/dense.jl b/stdlib/LinearAlgebra/test/dense.jl
@@ -395,6 +395,19 @@ end
     @test kron(b',2) == [8 10 12]
 end
 
+@testset "kron!" begin
+    a = [1.0, 0.0]
+    b = [0.0, 1.0]
+    @test kron!([1.0, 0.0], b, 0.5) == [0.0; 0.5]
+    @test kron!([1.0, 0.0], 0.5, b) == [0.0; 0.5]
+    c = Vector{Float64}(undef, 4)
+    kron!(c, a, b)
+    @test c == [0.0; 1.0; 0.0; 0.0]
+    c = Matrix{Float64}(undef, 2, 2)
+    kron!(c, a, b')
+    @test c == [0.0 1.0; 0.0 0.0]
+end
+
 @testset "kron adjoint" begin
     a = [1+im, 2, 3]
     b = [4, 5, 6+7im]