[petsc-users] strange convergence
Hoang Giang Bui
hgbk2008 at gmail.com
Mon Apr 24 17:10:49 CDT 2017
It took a while, here I send you the output
0 KSP preconditioned resid norm 3.129073545457e+05 true resid norm
9.015150492169e+06 ||r(i)||/||b|| 1.000000000000e+00
1 KSP preconditioned resid norm 7.442444222843e-01 true resid norm
1.003356247696e+02 ||r(i)||/||b|| 1.112966720375e-05
2 KSP preconditioned resid norm 3.267453132529e-07 true resid norm
3.216722968300e+01 ||r(i)||/||b|| 3.568130084011e-06
3 KSP preconditioned resid norm 1.155046883816e-11 true resid norm
3.234460376820e+01 ||r(i)||/||b|| 3.587805194854e-06
Linear solve converged due to CONVERGED_ATOL iterations 3
KSP Object: 4 MPI processes
type: gmres
GMRES: restart=1000, using Modified Gram-Schmidt Orthogonalization
GMRES: happy breakdown tolerance 1e-30
maximum iterations=1000, initial guess is zero
tolerances: relative=1e-20, absolute=1e-09, divergence=10000
left preconditioning
using PRECONDITIONED norm type for convergence test
PC Object: 4 MPI processes
type: lu
LU: out-of-place factorization
tolerance for zero pivot 2.22045e-14
matrix ordering: natural
factor fill ratio given 0, needed 0
Factored matrix follows:
Mat Object: 4 MPI processes
type: mpiaij
rows=973051, cols=973051
package used to perform factorization: pastix
Error : 3.24786e-14
total: nonzeros=0, allocated nonzeros=0
total number of mallocs used during MatSetValues calls =0
PaStiX run parameters:
Matrix type : Unsymmetric
Level of printing (0,1,2): 0
Number of refinements iterations : 3
Error : 3.24786e-14
linear system matrix = precond matrix:
Mat Object: 4 MPI processes
type: mpiaij
rows=973051, cols=973051
Error : 3.24786e-14
total: nonzeros=9.90037e+07, allocated nonzeros=9.90037e+07
total number of mallocs used during MatSetValues calls =0
using I-node (on process 0) routines: found 78749 nodes, limit used
is 5
Error : 3.24786e-14
It doesn't do as you said. Something is not right here. I will look in
depth.
Giang
On Mon, Apr 24, 2017 at 8:21 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
> > On Apr 24, 2017, at 12:47 PM, Hoang Giang Bui <hgbk2008 at gmail.com>
> wrote:
> >
> > Good catch. I get this for the very first step, maybe at that time the
> rhs_w is zero.
>
> With the multiplicative composition the right hand side of the second
> solve is the initial right hand side of the second solve minus A_10*x where
> x is the solution to the first sub solve and A_10 is the lower left block
> of the outer matrix. So unless both the initial right hand side has a zero
> for the second block and A_10 is identically zero the right hand side for
> the second sub solve should not be zero. Is A_10 == 0?
>
>
> > In the later step, it shows 2 step convergence
> >
> > Residual norms for fieldsplit_u_ solve.
> > 0 KSP Residual norm 3.165886479830e+04
> > 1 KSP Residual norm 2.905922877684e-01
> > Residual norms for fieldsplit_wp_ solve.
> > 0 KSP Residual norm 2.397669419027e-01
> > 1 KSP Residual norm 0.000000000000e+00
> > 0 KSP preconditioned resid norm 3.165886479920e+04 true resid norm
> 7.963616922323e+05 ||r(i)||/||b|| 1.000000000000e+00
> > Residual norms for fieldsplit_u_ solve.
> > 0 KSP Residual norm 9.999891813771e-01
> > 1 KSP Residual norm 1.512000395579e-05
> > Residual norms for fieldsplit_wp_ solve.
> > 0 KSP Residual norm 8.192702188243e-06
> > 1 KSP Residual norm 0.000000000000e+00
> > 1 KSP preconditioned resid norm 5.252183822848e-02 true resid norm
> 7.135927677844e+04 ||r(i)||/||b|| 8.960661653427e-02
>
> The outer residual norms are still wonky, the preconditioned residual
> norm goes from 3.165886479920e+04 to 5.252183822848e-02 which is a huge
> drop but the 7.963616922323e+05 drops very much less 7.135927677844e+04.
> This is not normal.
>
> What if you just use -pc_type lu for the entire system (no fieldsplit),
> does the true residual drop to almost zero in the first iteration (as it
> should?). Send the output.
>
>
>
> > Residual norms for fieldsplit_u_ solve.
> > 0 KSP Residual norm 6.946213936597e-01
> > 1 KSP Residual norm 1.195514007343e-05
> > Residual norms for fieldsplit_wp_ solve.
> > 0 KSP Residual norm 1.025694497535e+00
> > 1 KSP Residual norm 0.000000000000e+00
> > 2 KSP preconditioned resid norm 8.785709535405e-03 true resid norm
> 1.419341799277e+04 ||r(i)||/||b|| 1.782282866091e-02
> > Residual norms for fieldsplit_u_ solve.
> > 0 KSP Residual norm 7.255149996405e-01
> > 1 KSP Residual norm 6.583512434218e-06
> > Residual norms for fieldsplit_wp_ solve.
> > 0 KSP Residual norm 1.015229700337e+00
> > 1 KSP Residual norm 0.000000000000e+00
> > 3 KSP preconditioned resid norm 7.110407712709e-04 true resid norm
> 5.284940654154e+02 ||r(i)||/||b|| 6.636357205153e-04
> > Residual norms for fieldsplit_u_ solve.
> > 0 KSP Residual norm 3.512243341400e-01
> > 1 KSP Residual norm 2.032490351200e-06
> > Residual norms for fieldsplit_wp_ solve.
> > 0 KSP Residual norm 1.282327290982e+00
> > 1 KSP Residual norm 0.000000000000e+00
> > 4 KSP preconditioned resid norm 3.482036620521e-05 true resid norm
> 4.291231924307e+01 ||r(i)||/||b|| 5.388546393133e-05
> > Residual norms for fieldsplit_u_ solve.
> > 0 KSP Residual norm 3.423609338053e-01
> > 1 KSP Residual norm 4.213703301972e-07
> > Residual norms for fieldsplit_wp_ solve.
> > 0 KSP Residual norm 1.157384757538e+00
> > 1 KSP Residual norm 0.000000000000e+00
> > 5 KSP preconditioned resid norm 1.203470314534e-06 true resid norm
> 4.544956156267e+00 ||r(i)||/||b|| 5.707150658550e-06
> > Residual norms for fieldsplit_u_ solve.
> > 0 KSP Residual norm 3.838596289995e-01
> > 1 KSP Residual norm 9.927864176103e-08
> > Residual norms for fieldsplit_wp_ solve.
> > 0 KSP Residual norm 1.066298905618e+00
> > 1 KSP Residual norm 0.000000000000e+00
> > 6 KSP preconditioned resid norm 3.331619244266e-08 true resid norm
> 2.821511729024e+00 ||r(i)||/||b|| 3.543002829675e-06
> > Residual norms for fieldsplit_u_ solve.
> > 0 KSP Residual norm 4.624964188094e-01
> > 1 KSP Residual norm 6.418229775372e-08
> > Residual norms for fieldsplit_wp_ solve.
> > 0 KSP Residual norm 9.800784311614e-01
> > 1 KSP Residual norm 0.000000000000e+00
> > 7 KSP preconditioned resid norm 8.788046233297e-10 true resid norm
> 2.849209671705e+00 ||r(i)||/||b|| 3.577783436215e-06
> > Linear solve converged due to CONVERGED_ATOL iterations 7
> >
> > The outer operator is an explicit matrix.
> >
> > Giang
> >
> > On Mon, Apr 24, 2017 at 7:32 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> >
> > > On Apr 24, 2017, at 3:16 AM, Hoang Giang Bui <hgbk2008 at gmail.com>
> wrote:
> > >
> > > Thanks Barry, trying with -fieldsplit_u_type lu gives better
> convergence. I still used 4 procs though, probably with 1 proc it should
> also be the same.
> > >
> > > The u block used a Nitsche-type operator to connect two non-matching
> domains. I don't think it will leave some rigid body motion leads to not
> sufficient constraints. Maybe you have other idea?
> > >
> > > Residual norms for fieldsplit_u_ solve.
> > > 0 KSP Residual norm 3.129067184300e+05
> > > 1 KSP Residual norm 5.906261468196e-01
> > > Residual norms for fieldsplit_wp_ solve.
> > > 0 KSP Residual norm 0.000000000000e+00
> >
> > ^^^^ something is wrong here. The sub solve should not be starting
> with a 0 residual (this means the right hand side for this sub solve is
> zero which it should not be).
> >
> > > FieldSplit with MULTIPLICATIVE composition: total splits = 2
> >
> >
> > How are you providing the outer operator? As an explicit matrix or
> with some shell matrix?
> >
> >
> >
> > > 0 KSP preconditioned resid norm 3.129067184300e+05 true resid norm
> 9.015150492169e+06 ||r(i)||/||b|| 1.000000000000e+00
> > > Residual norms for fieldsplit_u_ solve.
> > > 0 KSP Residual norm 9.999955993437e-01
> > > 1 KSP Residual norm 4.019774691831e-06
> > > Residual norms for fieldsplit_wp_ solve.
> > > 0 KSP Residual norm 0.000000000000e+00
> > > 1 KSP preconditioned resid norm 5.003913641475e-01 true resid norm
> 4.692996324114e+01 ||r(i)||/||b|| 5.205677185522e-06
> > > Residual norms for fieldsplit_u_ solve.
> > > 0 KSP Residual norm 1.000012180204e+00
> > > 1 KSP Residual norm 1.017367950422e-05
> > > Residual norms for fieldsplit_wp_ solve.
> > > 0 KSP Residual norm 0.000000000000e+00
> > > 2 KSP preconditioned resid norm 2.330910333756e-07 true resid norm
> 3.474855463983e+01 ||r(i)||/||b|| 3.854461960453e-06
> > > Residual norms for fieldsplit_u_ solve.
> > > 0 KSP Residual norm 1.000004200085e+00
> > > 1 KSP Residual norm 6.231613102458e-06
> > > Residual norms for fieldsplit_wp_ solve.
> > > 0 KSP Residual norm 0.000000000000e+00
> > > 3 KSP preconditioned resid norm 8.671259838389e-11 true resid norm
> 3.545103468011e+01 ||r(i)||/||b|| 3.932384125024e-06
> > > Linear solve converged due to CONVERGED_ATOL iterations 3
> > > KSP Object: 4 MPI processes
> > > type: gmres
> > > GMRES: restart=1000, using Modified Gram-Schmidt Orthogonalization
> > > GMRES: happy breakdown tolerance 1e-30
> > > maximum iterations=1000, initial guess is zero
> > > tolerances: relative=1e-20, absolute=1e-09, divergence=10000
> > > left preconditioning
> > > using PRECONDITIONED norm type for convergence test
> > > PC Object: 4 MPI processes
> > > type: fieldsplit
> > > FieldSplit with MULTIPLICATIVE composition: total splits = 2
> > > Solver info for each split is in the following KSP objects:
> > > Split number 0 Defined by IS
> > > KSP Object: (fieldsplit_u_) 4 MPI processes
> > > type: richardson
> > > Richardson: damping factor=1
> > > maximum iterations=1, initial guess is zero
> > > tolerances: relative=1e-05, absolute=1e-50, divergence=10000
> > > left preconditioning
> > > using PRECONDITIONED norm type for convergence test
> > > PC Object: (fieldsplit_u_) 4 MPI processes
> > > type: lu
> > > LU: out-of-place factorization
> > > tolerance for zero pivot 2.22045e-14
> > > matrix ordering: natural
> > > factor fill ratio given 0, needed 0
> > > Factored matrix follows:
> > > Mat Object: 4 MPI processes
> > > type: mpiaij
> > > rows=938910, cols=938910
> > > package used to perform factorization: pastix
> > > total: nonzeros=0, allocated nonzeros=0
> > > Error : 3.36878e-14
> > > total number of mallocs used during MatSetValues calls =0
> > > PaStiX run parameters:
> > > Matrix type : Unsymmetric
> > > Level of printing (0,1,2): 0
> > > Number of refinements iterations : 3
> > > Error : 3.36878e-14
> > > linear system matrix = precond matrix:
> > > Mat Object: (fieldsplit_u_) 4 MPI processes
> > > type: mpiaij
> > > rows=938910, cols=938910, bs=3
> > > Error : 3.36878e-14
> > > Error : 3.36878e-14
> > > total: nonzeros=8.60906e+07, allocated nonzeros=8.60906e+07
> > > total number of mallocs used during MatSetValues calls =0
> > > using I-node (on process 0) routines: found 78749 nodes,
> limit used is 5
> > > Split number 1 Defined by IS
> > > KSP Object: (fieldsplit_wp_) 4 MPI processes
> > > type: richardson
> > > Richardson: damping factor=1
> > > maximum iterations=1, initial guess is zero
> > > tolerances: relative=1e-05, absolute=1e-50, divergence=10000
> > > left preconditioning
> > > using PRECONDITIONED norm type for convergence test
> > > PC Object: (fieldsplit_wp_) 4 MPI processes
> > > type: lu
> > > LU: out-of-place factorization
> > > tolerance for zero pivot 2.22045e-14
> > > matrix ordering: natural
> > > factor fill ratio given 0, needed 0
> > > Factored matrix follows:
> > > Mat Object: 4 MPI processes
> > > type: mpiaij
> > > rows=34141, cols=34141
> > > package used to perform factorization: pastix
> > > Error : -nan
> > > Error : -nan
> > > Error : -nan
> > > total: nonzeros=0, allocated nonzeros=0
> > > total number of mallocs used during MatSetValues calls =0
> > > PaStiX run parameters:
> > > Matrix type : Symmetric
> > > Level of printing (0,1,2): 0
> > > Number of refinements iterations : 0
> > > Error : -nan
> > > linear system matrix = precond matrix:
> > > Mat Object: (fieldsplit_wp_) 4 MPI processes
> > > type: mpiaij
> > > rows=34141, cols=34141
> > > total: nonzeros=485655, allocated nonzeros=485655
> > > total number of mallocs used during MatSetValues calls =0
> > > not using I-node (on process 0) routines
> > > linear system matrix = precond matrix:
> > > Mat Object: 4 MPI processes
> > > type: mpiaij
> > > rows=973051, cols=973051
> > > total: nonzeros=9.90037e+07, allocated nonzeros=9.90037e+07
> > > total number of mallocs used during MatSetValues calls =0
> > > using I-node (on process 0) routines: found 78749 nodes, limit
> used is 5
> > >
> > >
> > >
> > > Giang
> > >
> > > On Sun, Apr 23, 2017 at 10:19 PM, Barry Smith <bsmith at mcs.anl.gov>
> wrote:
> > >
> > > > On Apr 23, 2017, at 2:42 PM, Hoang Giang Bui <hgbk2008 at gmail.com>
> wrote:
> > > >
> > > > Dear Matt/Barry
> > > >
> > > > With your options, it results in
> > > >
> > > > 0 KSP preconditioned resid norm 1.106709687386e+31 true resid norm
> 9.015150491938e+06 ||r(i)||/||b|| 1.000000000000e+00
> > > > Residual norms for fieldsplit_u_ solve.
> > > > 0 KSP Residual norm 2.407308987203e+36
> > > > 1 KSP Residual norm 5.797185652683e+72
> > >
> > > It looks like Matt is right, hypre is seemly producing useless garbage.
> > >
> > > First how do things run on one process. If you have similar problems
> then debug on one process (debugging any kind of problem is always far easy
> on one process).
> > >
> > > First run with -fieldsplit_u_type lu (instead of using hypre) to see
> if that works or also produces something bad.
> > >
> > > What is the operator and the boundary conditions for u? It could be
> singular.
> > >
> > >
> > >
> > >
> > >
> > >
> > > > Residual norms for fieldsplit_wp_ solve.
> > > > 0 KSP Residual norm 0.000000000000e+00
> > > > ...
> > > > 999 KSP preconditioned resid norm 2.920157329174e+12 true resid norm
> 9.015683504616e+06 ||r(i)||/||b|| 1.000059124102e+00
> > > > Residual norms for fieldsplit_u_ solve.
> > > > 0 KSP Residual norm 1.533726746719e+36
> > > > 1 KSP Residual norm 3.692757392261e+72
> > > > Residual norms for fieldsplit_wp_ solve.
> > > > 0 KSP Residual norm 0.000000000000e+00
> > > >
> > > > Do you suggest that the pastix solver for the "wp" block encounters
> small pivot? In addition, seem like the "u" block is also singular.
> > > >
> > > > Giang
> > > >
> > > > On Sun, Apr 23, 2017 at 7:39 PM, Barry Smith <bsmith at mcs.anl.gov>
> wrote:
> > > >
> > > > Huge preconditioned norms but normal unpreconditioned norms
> almost always come from a very small pivot in an LU or ILU factorization.
> > > >
> > > > The first thing to do is monitor the two sub solves. Run with the
> additional options -fieldsplit_u_ksp_type richardson
> -fieldsplit_u_ksp_monitor -fieldsplit_u_ksp_max_it 1
> -fieldsplit_wp_ksp_type richardson -fieldsplit_wp_ksp_monitor
> -fieldsplit_wp_ksp_max_it 1
> > > >
> > > > > On Apr 23, 2017, at 12:22 PM, Hoang Giang Bui <hgbk2008 at gmail.com>
> wrote:
> > > > >
> > > > > Hello
> > > > >
> > > > > I encountered a strange convergence behavior that I have trouble
> to understand
> > > > >
> > > > > KSPSetFromOptions completed
> > > > > 0 KSP preconditioned resid norm 1.106709687386e+31 true resid
> norm 9.015150491938e+06 ||r(i)||/||b|| 1.000000000000e+00
> > > > > 1 KSP preconditioned resid norm 2.933141742664e+29 true resid
> norm 9.015152282123e+06 ||r(i)||/||b|| 1.000000198575e+00
> > > > > 2 KSP preconditioned resid norm 9.686409637174e+16 true resid
> norm 9.015354521944e+06 ||r(i)||/||b|| 1.000022631902e+00
> > > > > 3 KSP preconditioned resid norm 4.219243615809e+15 true resid
> norm 9.017157702420e+06 ||r(i)||/||b|| 1.000222648583e+00
> > > > > .....
> > > > > 999 KSP preconditioned resid norm 3.043754298076e+12 true resid
> norm 9.015425041089e+06 ||r(i)||/||b|| 1.000030454195e+00
> > > > > 1000 KSP preconditioned resid norm 3.043000287819e+12 true resid
> norm 9.015424313455e+06 ||r(i)||/||b|| 1.000030373483e+00
> > > > > Linear solve did not converge due to DIVERGED_ITS iterations 1000
> > > > > KSP Object: 4 MPI processes
> > > > > type: gmres
> > > > > GMRES: restart=1000, using Modified Gram-Schmidt
> Orthogonalization
> > > > > GMRES: happy breakdown tolerance 1e-30
> > > > > maximum iterations=1000, initial guess is zero
> > > > > tolerances: relative=1e-20, absolute=1e-09, divergence=10000
> > > > > left preconditioning
> > > > > using PRECONDITIONED norm type for convergence test
> > > > > PC Object: 4 MPI processes
> > > > > type: fieldsplit
> > > > > FieldSplit with MULTIPLICATIVE composition: total splits = 2
> > > > > Solver info for each split is in the following KSP objects:
> > > > > Split number 0 Defined by IS
> > > > > KSP Object: (fieldsplit_u_) 4 MPI processes
> > > > > type: preonly
> > > > > maximum iterations=10000, initial guess is zero
> > > > > tolerances: relative=1e-05, absolute=1e-50, divergence=10000
> > > > > left preconditioning
> > > > > using NONE norm type for convergence test
> > > > > PC Object: (fieldsplit_u_) 4 MPI processes
> > > > > type: hypre
> > > > > HYPRE BoomerAMG preconditioning
> > > > > HYPRE BoomerAMG: Cycle type V
> > > > > HYPRE BoomerAMG: Maximum number of levels 25
> > > > > HYPRE BoomerAMG: Maximum number of iterations PER hypre
> call 1
> > > > > HYPRE BoomerAMG: Convergence tolerance PER hypre call 0
> > > > > HYPRE BoomerAMG: Threshold for strong coupling 0.6
> > > > > HYPRE BoomerAMG: Interpolation truncation factor 0
> > > > > HYPRE BoomerAMG: Interpolation: max elements per row 0
> > > > > HYPRE BoomerAMG: Number of levels of aggressive coarsening
> 0
> > > > > HYPRE BoomerAMG: Number of paths for aggressive coarsening
> 1
> > > > > HYPRE BoomerAMG: Maximum row sums 0.9
> > > > > HYPRE BoomerAMG: Sweeps down 1
> > > > > HYPRE BoomerAMG: Sweeps up 1
> > > > > HYPRE BoomerAMG: Sweeps on coarse 1
> > > > > HYPRE BoomerAMG: Relax down symmetric-SOR/Jacobi
> > > > > HYPRE BoomerAMG: Relax up symmetric-SOR/Jacobi
> > > > > HYPRE BoomerAMG: Relax on coarse Gaussian-elimination
> > > > > HYPRE BoomerAMG: Relax weight (all) 1
> > > > > HYPRE BoomerAMG: Outer relax weight (all) 1
> > > > > HYPRE BoomerAMG: Using CF-relaxation
> > > > > HYPRE BoomerAMG: Measure type local
> > > > > HYPRE BoomerAMG: Coarsen type PMIS
> > > > > HYPRE BoomerAMG: Interpolation type classical
> > > > > linear system matrix = precond matrix:
> > > > > Mat Object: (fieldsplit_u_) 4 MPI processes
> > > > > type: mpiaij
> > > > > rows=938910, cols=938910, bs=3
> > > > > total: nonzeros=8.60906e+07, allocated nonzeros=8.60906e+07
> > > > > total number of mallocs used during MatSetValues calls =0
> > > > > using I-node (on process 0) routines: found 78749 nodes,
> limit used is 5
> > > > > Split number 1 Defined by IS
> > > > > KSP Object: (fieldsplit_wp_) 4 MPI processes
> > > > > type: preonly
> > > > > maximum iterations=10000, initial guess is zero
> > > > > tolerances: relative=1e-05, absolute=1e-50, divergence=10000
> > > > > left preconditioning
> > > > > using NONE norm type for convergence test
> > > > > PC Object: (fieldsplit_wp_) 4 MPI processes
> > > > > type: lu
> > > > > LU: out-of-place factorization
> > > > > tolerance for zero pivot 2.22045e-14
> > > > > matrix ordering: natural
> > > > > factor fill ratio given 0, needed 0
> > > > > Factored matrix follows:
> > > > > Mat Object: 4 MPI processes
> > > > > type: mpiaij
> > > > > rows=34141, cols=34141
> > > > > package used to perform factorization: pastix
> > > > > Error : -nan
> > > > > Error : -nan
> > > > > total: nonzeros=0, allocated nonzeros=0
> > > > > Error : -nan
> > > > > total number of mallocs used during MatSetValues calls =0
> > > > > PaStiX run parameters:
> > > > > Matrix type : Symmetric
> > > > > Level of printing (0,1,2): 0
> > > > > Number of refinements iterations : 0
> > > > > Error : -nan
> > > > > linear system matrix = precond matrix:
> > > > > Mat Object: (fieldsplit_wp_) 4 MPI processes
> > > > > type: mpiaij
> > > > > rows=34141, cols=34141
> > > > > total: nonzeros=485655, allocated nonzeros=485655
> > > > > total number of mallocs used during MatSetValues calls =0
> > > > > not using I-node (on process 0) routines
> > > > > linear system matrix = precond matrix:
> > > > > Mat Object: 4 MPI processes
> > > > > type: mpiaij
> > > > > rows=973051, cols=973051
> > > > > total: nonzeros=9.90037e+07, allocated nonzeros=9.90037e+07
> > > > > total number of mallocs used during MatSetValues calls =0
> > > > > using I-node (on process 0) routines: found 78749 nodes,
> limit used is 5
> > > > >
> > > > > The pattern of convergence gives a hint that this system is
> somehow bad/singular. But I don't know why the preconditioned error goes up
> too high. Anyone has an idea?
> > > > >
> > > > > Best regards
> > > > > Giang Bui
> > > > >
> > > >
> > > >
> > >
> > >
> >
> >
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20170425/ef06d17b/attachment-0001.html>
More information about the petsc-users
mailing list