Hi,
I encountered the following error while solving a symmetric positive
defined system:
Linear solve did not converge due to DIVERGED_PCSETUP_FAILED iterations
0
PCSETUP_FAILED due to SUBPC_ERROR
This error appears only if I use the optimized version of both petsc
and my code ( compiler: gfortran, flags: -O3 ).
It is weird since I am solving a time-dependent problem and everything,
i.e. results and convergence rate, are as expected until the above error
shows up. If I run both petsc and my code in debug mode, everything goes
smooth till the end of the simulation.
However, if I reduce the ksp_rtol, even the debug run fails, after
running as expected for a while, because of a
KSP_DIVERGED_INDEFINITE_PC .
The options I am using are:
-ksp_type cg
-ksp_norm_type unpreconditioned
-ksp_rtol 1e-8
-ksp_lag_norm
-ksp_initial_guess_nonzero yes
-pc_type mg
-pc_mg_galerkin
-pc_mg_levels 4
-mg_levels_ksp_type richardson
-mg_coarse_ksp_constant_null_space
-mg_coarse_pc_type lu
-mg_coarse_pc_factor_mat_solver_package superlu_dist
-options_left
I attached a copy of ksp_view. I am currently using petsc-master (last
updated yesterday).
I would appreciate any suggestion on this matter.
Thanks,
Michele
KSP Object: 1 MPI processes
type: cg
maximum iterations=10000
tolerances: relative=1e-08, absolute=1e-50, divergence=10000.
left preconditioning
using nonzero initial guess
using UNPRECONDITIONED norm type for convergence test
PC Object: 1 MPI processes
type: mg
MG: type is MULTIPLICATIVE, levels=4 cycles=v
Cycles per PCApply=1
Using Galerkin computed coarse grid matrices
Coarse grid solver -- level -------------------------------
KSP Object: (mg_coarse_) 1 MPI processes
type: preonly
maximum iterations=1, initial guess is zero
tolerances: relative=1e-05, absolute=1e-50, divergence=10000.
left preconditioning
using NONE norm type for convergence test
PC Object: (mg_coarse_) 1 MPI processes
type: lu
LU: out-of-place factorization
tolerance for zero pivot 2.22045e-14
using diagonal shift on blocks to prevent zero pivot [INBLOCKS]
matrix ordering: nd
factor fill ratio given 0., needed 0.
Factored matrix follows:
Mat Object: 1 MPI processes
type: seqaij
rows=16, cols=16
package used to perform factorization: superlu_dist
total: nonzeros=0, allocated nonzeros=0
total number of mallocs used during MatSetValues calls =0
SuperLU_DIST run parameters:
Process grid nprow 1 x npcol 1
Equilibrate matrix TRUE
Matrix input mode 0
Replace tiny pivots FALSE
Use iterative refinement FALSE
Processors in row 1 col partition 1
Row permutation LargeDiag
Column permutation METIS_AT_PLUS_A
Parallel symbolic factorization FALSE
Repeated factorization SamePattern
linear system matrix = precond matrix:
Mat Object: 1 MPI processes
type: seqaij
rows=16, cols=16
total: nonzeros=72, allocated nonzeros=72
total number of mallocs used during MatSetValues calls =0
not using I-node routines
Down solver (pre-smoother) on level 1 -------------------------------
KSP Object: (mg_levels_1_) 1 MPI processes
type: richardson
Richardson: damping factor=1.
maximum iterations=2
tolerances: relative=1e-05, absolute=1e-50, divergence=10000.
left preconditioning
using nonzero initial guess
using NONE norm type for convergence test
PC Object: (mg_levels_1_) 1 MPI processes
type: sor
SOR: type = local_symmetric, iterations = 1, local iterations = 1,
omega = 1.
linear system matrix = precond matrix:
Mat Object: 1 MPI processes
type: seqaij
rows=64, cols=64
total: nonzeros=304, allocated nonzeros=304
total number of mallocs used during MatSetValues calls =0
not using I-node routines
Up solver (post-smoother) same as down solver (pre-smoother)
Down solver (pre-smoother) on level 2 -------------------------------
KSP Object: (mg_levels_2_) 1 MPI processes
type: richardson
Richardson: damping factor=1.
maximum iterations=2
tolerances: relative=1e-05, absolute=1e-50, divergence=10000.
left preconditioning
using nonzero initial guess
using NONE norm type for convergence test
PC Object: (mg_levels_2_) 1 MPI processes
type: sor
SOR: type = local_symmetric, iterations = 1, local iterations = 1,
omega = 1.
linear system matrix = precond matrix:
Mat Object: 1 MPI processes
type: seqaij
rows=256, cols=256
total: nonzeros=1248, allocated nonzeros=1248
total number of mallocs used during MatSetValues calls =0
not using I-node routines
Up solver (post-smoother) same as down solver (pre-smoother)
Down solver (pre-smoother) on level 3 -------------------------------
KSP Object: (mg_levels_3_) 1 MPI processes
type: richardson
Richardson: damping factor=1.
maximum iterations=2
tolerances: relative=1e-05, absolute=1e-50, divergence=10000.
left preconditioning
using nonzero initial guess
using NONE norm type for convergence test
PC Object: (mg_levels_3_) 1 MPI processes
type: sor
SOR: type = local_symmetric, iterations = 1, local iterations = 1,
omega = 1.
linear system matrix = precond matrix:
Mat Object: 1 MPI processes
type: seqaij
rows=1024, cols=1024
total: nonzeros=5056, allocated nonzeros=5056
total number of mallocs used during MatSetValues calls =0
has attached null space
not using I-node routines
Up solver (post-smoother) same as down solver (pre-smoother)
linear system matrix = precond matrix:
Mat Object: 1 MPI processes
type: seqaij
rows=1024, cols=1024
total: nonzeros=5056, allocated nonzeros=5056
total number of mallocs used during MatSetValues calls =0
has attached null space
not using I-node routines
