Changed meaning of .+= in Julia 0.5

[stevengj]

Your test program uses x .+= y, so you should know that in Julia 0.5 this has changed meaning to be equivalent to broadcast!(identity, x, x .+ y), so that it mutates the x array (see JuliaLang/julia#17510 … in Julia 0.6 the whole operation will occur in-place without temporaries). So .+ should only be used if the left-hand side is a mutable array, and you don't mind mutating it.

At first glance, this looks like a problem for you, because the left-hand-side in x_exp[rx] .+= y0[ry] is just a number, not mutable? If that is the case, you can just change it to +=.