[julia-users] Re: push! performance

[David P. Sanders]

El domingo, 15 de noviembre de 2015, 17:35:45 (UTC-6), Steven G. Johnson 
escribió:
>
> function prealloc(n)
>     a = Array(Int, n)
>     for i = 1:n
>         a[i] = i
>     end
>     return a
> end
> function dynamic(n)
>     a = Int[]
>     for i = 1:n
>         push!(a, i)
>     end
>     return a
> end
> @time prealloc(10^7);
> @time dynamic(10^7);
>
>
> On my machine, the preallocated version is 2.5–3x faster.  A significant 
> but not overwhelming margin.
>

However, if you are doing actual calculations inside the loop 
(rather than just storing the values), then in my experience the 
performance difference is much smaller.