The quasi-best MaxN function

General Usage Performance
12

You can still squeeze a little bit by removing the array access maxn[N] in the loop.

function MaxN6c2(cr,N)
    maxn = sort!(cr[1:N], rev=true)
    maxnN = maxn[N]
    @inbounds for i in N+1:length(cr)
        e=cr[i]
        if maxnN < e
            insert1(maxn,N,e)
            maxnN = maxn[N]
        end
    end
    maxn
end

julia> @btime MaxN6c2($re6, 20);
  555.000 μs (203 allocations: 32.78 KiB)
julia> @btime MaxN6c1($re6, 20);
  735.699 μs (203 allocations: 32.78 KiB)
julia> @btime nlargest(20, $re6);
  858.300 μs (2 allocations: 480 bytes)

(This would probably apply to nlargest as well.)