Julia style? Arrays/matrix vs structs

General Usage
14

Let’s make things a little bit more interesting by throwing in regular arrays
and increasing the size of the data structure.

using StaticArrays

struct Point3D{T} <: FieldVector{3, T}
    x::T
    y::T
    z::T
end

mutable struct MPoint3D{T} <: FieldVector{3, T}
    x::T
    y::T
    z::T
end

function f1!(v)
    for i in eachindex(v)
        x, y, z = v[i]
        v[i] = Point3D(2x, x*y, x*z)
    end
end

function f2!(v)
    for i in eachindex(v)
        x, y, z = v[i]
        v[i] .= (2x, x*y, x*z)
    end
end

function f5!(v)
    for i in 1:size(v, 1)
        x, y, z = v[i, 1], v[i, 2], v[i, 3]
        v[i, 1], v[i, 2], v[i, 3] = 2x, x*y, x*z
    end
end

function f6!(v)
    for i in 1:size(v, 2)
        x, y, z = v[1, i], v[2, i], v[3, i]
        v[1, i], v[2, i], v[3, i] = 2x, x*y, x*z
    end
end

using BenchmarkTools
v1 = [@SVector(rand(3)) for i = 1:1000000]
v2 = [@MVector(rand(3)) for i = 1:1000000]
v3 = [Point3D(rand(3))  for i = 1:1000000]
v4 = [MPoint3D(rand(3)) for i = 1:1000000]
v5 = rand(1000000, 3)
v6 = rand(3, 1000000)

@btime f1!($v1)   # 1.693 ms (0 allocations: 0 bytes)  
@btime f2!($v2)  # 2.821 ms (0 allocations: 0 bytes)  

@btime f1!($v3)  # 1.728 ms (0 allocations: 0 bytes)     
@btime f2!($v4)  # 57.962 ms (3000000 allocations: 45.78 MiB)   

@btime f5!($v5)  # 1.518 ms (0 allocations: 0 bytes)  
@btime f6!($v6)    # 1.739 ms (0 allocations: 0 bytes)