To add some data to this conversation, I just timed allocating a billion Int64s on my macbook, and I got this (I ran these multiple times before this and got similar timings):
julia> N=1_000_000_000 1000000000 julia> @time x = Array(Int64,N); elapsed time: 0.022577671 seconds (8000000128 bytes allocated) julia> @time x = zeros(Int64,N); elapsed time: 3.95432248 seconds (8000000152 bytes allocated) So we are talking adding possibly seconds to a program per large array allocation.
