Hi all
Because of a combination of settings, our code passes through this line:
i.e. the matrices associated with each of the sub-KSPs of a fieldsplit are destroyed and then re-created later.The thing is that one of these destroyed matrices had a near nullspace attached, which is lost because the new matrix does not have it anymore.
Is this a bug or are we missing something?
I just want to get a clear picture. You create a PCFIELDSPLIT, set it up, then pull out the matrices and attach a nullspace before the solve. At a later time, you start another solve with this PC, and it has the DIFFERENT_NONZERO_PATTERN flag, so it recreates these matrices and loses your attached nullspace.
First, does the matrix really change?
Second, I had the same problem. I added callbacks to DM which allow a nullspace to be automatically attached if you extract a certain subfield. Are you using a DM?
Thanks,
Matt
I'll need some time to come up with a MWE showing how the near nullspace is lost, but if its needed I can take a stab at it.
--jeremy
