Re: [firedrake] Difference between u.split() and split(u)

On 4 Nov 2015, at 14:51, Buesing, Henrik <HBuesing@eonerc.rwth-aachen.de> wrote:

Dear all,

I have a multi-physics problem and u is my unknown. I was wondering what the difference between

u.split() and split(u)

is.

It seems that the Jacobian is only right, when I use split(u) and then further use this in subroutines. If I use u.split() my Jacobian is zero…

It is an ongoing issue that we would like to resolve! Rule of thumb: Use: split(u) if you're going to use the split things in UFL forms Use: u.split() if you want to be able to do point wise operations on the split fields, or output them. These two things result in different types of objects (but wrapping the same, underlying, coefficients). Lawrence