Dictionary construction is quite slow?

[Oscar_Smith]

I recommend reading Performance Tips · The Julia Language

function f(d,rands)
    for (i, r) in enumerate(rands)
        d[i] = r
    end
end
rands = rand(10^7)
@time  f(Dict{Int, Float64}(), rands);
0.857354 seconds (72 allocations: 541.170 MiB, 1.51% gc time)