What is the correct (fastest) way to assign a Function to another Function in python?

Question

f = Function(Q)
g = Function(Q)
f.vector()[:] = g.vector() #does this work in parallel?
f.vector()[:] = g.vector()[:]
f.vector().set_local(g.vector().array())
f.assign(g) #apparently this would break pointers to f.split()

Answer 1

I have tested this quite thoroughly and in my experience the fastest approach is none of the above, rather

f.vector().zero()
f.vector().axpy(1.0, g.vector())

All of the methods should work in parallel afaik.