Now everything makes sense, thank you!
I actually had the problem that if I have an unconnected node, it is not
taken into account when calculating without -snes_fd. So that is
probably due to the coloring based Jacobian calculation.
And the actual problem was that I did not completely follow Shri's
advise from the "Extra Variable in DMCircuit" thread from 2014 to
actually connect this node to the network.... With -snes_fd it was just
working anyway so I did not care until I looked at the code again yesterday.
So, when connecting the node everything runs smoothly :-)
On 09.11.2017 16:38, Jed Brown wrote:
Florian Kauer <[email protected]> writes:
Hi,
what is the SNES solver actually doing when you do not provide a
jacobian and not explicitly select either finite differencing
approximation or matrix-free Newton-Krylov method?
I just noticed that I mistakenly did this, but a good solution is found
anyway (and fast). So what is actually happening? Simple fixed-point
iteration?
Presumably you are using a DM that can provide a coloring, in which case
the sparse Jacobian is assembled using finite differencing with coloring.
