Broadcasting and function composition (circ)

General Usage
, ,
10

This approach is 4 times fast than the mapslices approach


using BenchmarkTools
function cumprod_exp(x)
    y = similar(x)
    foreach(
        [view(y, :, i) for i in 1:size(y, 2)],
        [view(x, :, i) for i in 1:size(x, 2)]
    ) do v, u
        cumprod!(v, exp.(u))
    end
    return y
end

@btime cumprod_exp($(rand(10, 100)))

You can make it even faster if x is no longer needed

function cumprod_exp(x)
    y = similar(x)
    foreach(
        [view(y, :, i) for i in 1:size(y, 2)],
        [view(x, :, i) for i in 1:size(x, 2)]
    ) do v, u
        u .= exp.(u)
        cumprod!(v, u)
    end
    return y
end

Note, that you can easily save even more time by preallocating y – this just avoids the vcats in mapslices