Specialize lmul!/rmul! for adjoint/transpose

Author: jishnub

src/adjtrans.jl

@@ -513,6 +513,9 @@ function _dot_nonrecursive(u, v)
     end
 end
 
+rmul!(X::AdjOrTrans, s::Number) = (rmul!(parent(X), s); X)
+lmul!(s::Number, X::AdjOrTrans) = (lmul!(s, parent(X)); 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)

test/adjtrans.jl

@@ -798,4 +798,14 @@ end
     end
 end
 
+@testset "lmul!/rmul! by numbers" begin
+    for A in (rand(4, 4), rand(ComplexF64,4,4),
+                fill([1 2; 3 4], 4, 4))
+        B = copy(A)
+        @test lmul!(2, B) == 2 * A
+        B .= A
+        @test rmul!(B, 2) == A * 2
+    end
+end
+
 end # module TestAdjointTranspose