[julia-users] why sum(abs(A)) is very slow

[K Leo]

A is a 1-dimensional array.  I used to compute sum(abs(A)).  But when I 
changed to the following, the speed increased nearly 10 fold.  Why is that?

    sumA=0
    for i=1:length(A)
        sumA = sumA + abs(A[i])
    end