Tarrosion is right, on my machine, putting the code inside a function is 10X faster, and then swapping the order of the loops gives another 10X improvement:

Tarrosion is right, on my machine, putting the code inside a function is 10X faster, and then swapping the order of the loops gives another 10X improvement: function f(s) a=ones(s,s); b=ones(s,s); c=zeros(s,s); tic(); for j in 1:s for i in 1:s c[i,j]=a[i,j]*b[i,j] end end toc(); return c end Note that you also might have to run the function twice, because the first time JIT-compilation kicks in. Julia 0.5 also now automatically devectorizes some code (eg. x = a .* b .+ c) so that you don't have to write explicit loops to get performance benefits.