When trying things out I did try help(split), thinking maybe that was the problem. What I found is copied below. It is, let's say, terse.
I agree with Colin, if someone could insert something on the docs spelling out the difference that could be very helpful for other people who might very well come across the same issue.
Cheers, Francis
P.S. I will go back and reread old emails to understand why this is the correct syntax.
Help on function split in module ufl.split_functions:
split(v)
UFL operator: If v is a Coefficient or Argument in a mixed space, returns
a tuple with the function components corresponding to the subelements.
------------------
Francis Poulin
Associate Professor
Department of Applied Mathematics
University of Waterloo
email: fpoulin@uwaterloo.ca
Web: https://uwaterloo.ca/poulin-research-group/
Telephone: +1 519 888 4567 x32637
From: firedrake-bounces@imperial.ac.uk [firedrake-bounces@imperial.ac.uk] on behalf of Colin Cotter [colin.cotter@imperial.ac.uk]
Sent: Thursday, March 30, 2017 7:59 AM
To: firedrake
Subject: Re: [firedrake] close to fixing my nonlinear QG solver
Sent: Thursday, March 30, 2017 7:59 AM
To: firedrake
Subject: Re: [firedrake] close to fixing my nonlinear QG solver
It's a classic gotcha. We are kind of stuck with it due to wanting to stay close to the Fenics interface, but maybe we should have a specific bit in the docs about it [or a more highlighted one, if it already exists].
all the best
--cjc
On 30 March 2017 at 12:57, Francis Poulin
<fpoulin@uwaterloo.ca> wrote:
Houston, we have convergence!
Thank you for the help Lawrence.
I did see there were emails about the split passed around last week, which I clearly should have read more closely.
Now that I have convergence on a course grid I will test a finder grid and let you know how robust this is.
Cheers, Francis
------------------
Francis Poulin
Associate Professor
Department of Applied Mathematics
University of Waterloo
email: fpoulin@uwaterloo.ca
Web: https://uwaterloo.ca/poulin-research-group/
Telephone: +1 519 888 4567 x32637
________________________________________ Sent: Thursday, March 30, 2017 7:14 AM
From: firedrake-bounces@imperial.ac.uk [firedrake-bounces@imperial.ac.uk ] on behalf of Lawrence Mitchell [lawrence.mitchell@imperial.ac.uk ]
To: firedrake@imperial.ac.uk
Subject: Re: [firedrake] close to fixing my nonlinear QG solver
Hi Francis,
sorry, I now saw your problem.
You do:
soln1.assign(soln0)
psi1, u1, q1 = soln1.split()
Gnon = F(psi1, u1, q1)
You've been bitten by the "wrong split" bug!! ARGH.
Only use function.split() for output. If you're going to use the
split values in a form, you need to use "split(function)"
If you replace your lines:
psi1, u1, q1 = soln1.split()
Gnon = ...
with:
psi1, u1, q1 = split(soln1)
Gnon = ...
psi1, u1, q1 = soln1.split()
Everything works.
Lawrence
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