Julia multiply each matrix along dim

Question

I have a 3 dimensional array

x = rand(6,6,2^10)

I want to multiply each matrix along the third dimension by a vector. Is there a more clean way to do this than:

y = rand(6,1)
z = zeros(6,1,2^10)
for i in 1:2^10
    z[:,:,i] = x[:,:,i] * y
end

Answer 1

If you are working with matrices, it may be appropriate to consider x as a vector of matrices instead of a 3D array. Then you could do

x = [rand(6,6) for _ in 1:2^10]
y = [rand(6)]
z = x .* y

z is now a vector of vectors.

And if z is preallocated, that would be

z .= x .* y

And, if you want it really fast, use vectors of StaticArrays

using StaticArrays

x = [@SMatrix rand(6, 6) for _ in 1:2^10]
y = [@SVector rand(6)]
z = x .* y

That's showing a 10x speedup on my computer, running in 12us.