[CIG-SHORT] Question about message "fixing the coarse-level matrix dead dofs"

[Demian Gomez]

Dear all,

I'm working on refining/improving the mesh of one of my models and every
now and then, depending on the mesh I use, I get a message just before the
iterations of the quasi-static problem start: "[II] fixing the coarse-level
matrix dead dofs."

I've searched the message's string in Pylith's code and binaries and the
only place where it appears is in a PETSC library binary. I also searched
the PETSC's code but I was unable find the message at all. The problem runs
fine, converges and the outputs are OK, but still I'd like to understand
what this message means and if I need to take any action. Here is a more
"in context" (but still brief) output:

 >>
/home/demian/pylith-2.1.0/lib/python2.7/site-packages/pylith/problems/Formulation.py:601:_reformResidual
 -- implicit(debug)
 -- [6] CPU time: 00:04:09, Memory usage: 1529.86 MB
[II] fixing the coarse-level matrix dead dofs
  0 KSP Residual norm 1.667629230249e-01
  0 KSP preconditioned resid norm 1.667629230249e-01 true resid norm
2.680786441247e-01 ||r(i)||/||b|| 1.000000000000e+00
  1 KSP Residual norm 1.280993223073e-01
  1 KSP preconditioned resid norm 1.280993223073e-01 true resid norm
2.688535249989e-01 ||r(i)||/||b|| 1.002890498334e+00

[... iterations continue]

Here's the PETSC configuration I'm using:

[pylithapp.petsc]
ksp_rtol = 1.0e-8
fs_pc_type = fieldsplit
fs_pc_use_amat = true
fs_pc_fieldsplit_type = multiplicative
fs_fieldsplit_displacement_pc_type = ml
fs_fieldsplit_lagrange_multiplier_pc_type = jacobi
fs_fieldsplit_displacement_ksp_type = preonly
fs_fieldsplit_lagrange_multiplier_ksp_type = preonly

ksp_monitor = true
ksp_view = true
log_summary = true
ksp_max_it = 800
ksp_gmres_restart = 100
# start_in_debugger = true

snes_monitor = true
snes_view = true
ksp_converged_reason = true
snes_converged_reason = true
ksp_monitor_true_residual = true

Do you guys know the meaning of this message and if I should take any
action?

Thank you,
Demián

--
*Dr. Demián D. Gómez*
Postdoctoral Researcher
The Ohio State University - School of Earth Sciences
275 Mendenhall Laboratory
125 South Oval Mall
Columbus, Ohio 43210
Cell: +1 (901) 900-7324
email: gomez.124 at osu.edu
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