[petsc-users] PETSc KSPBCGSL with HYPRE boomeramg preconditioner ksp_monitor in poisson function
Hao Zhang
hbcbh1999 at gmail.com
Sun Sep 17 09:29:42 CDT 2017
Let me get more debugging information first. code were implemented in a
bunch of different files. simply copy-and-paste will make it very messy.
On Sun, Sep 17, 2017 at 1:38 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
> Send a code fragment that reproduces the problem; you must be calling on
> the wrong KSP or at the wrong place in the code
>
> > On Sep 17, 2017, at 12:33 AM, Hao Zhang <hbcbh1999 at gmail.com> wrote:
> >
> > Call KSPView(). this is I have from the output
> >
> > for my COARSE grid:
> >
> > imin = 4 imax = 41
> > jmin = 4 jmax = 8
> > kmin = 4 kmax = 20
> > KSP Object: 24 MPI processes
> > type not yet set
> > maximum iterations=20, initial guess is zero
> > tolerances: relative=1e-05, absolute=1e-50, divergence=10000
> > left preconditioning
> > using DEFAULT norm type for convergence test
> > PC Object: 24 MPI processes
> > type not yet set
> > PC has not been set up so information may be incomplete
> > KSP Object: 24 MPI processes
> > type not yet set
> > maximum iterations=20, initial guess is zero
> > tolerances: relative=1e-14, absolute=1e-50, divergence=10000
> > left preconditioning
> > using DEFAULT norm type for convergence test
> > PC Object: 24 MPI processes
> > type not yet set
> > PC has not been set up so information may be incomplete
> >
> > Using Neumann Solver
> > 0 KSP Residual norm 4.933753594518e+00
> > 2 KSP Residual norm 1.028883218492e-03
> > 4 KSP Residual norm 2.980337307701e-06
> > 6 KSP Residual norm 2.976110274418e-06
> > 8 KSP Residual norm 2.976110265786e-06
> > 10 KSP Residual norm 2.976110265696e-06
> > 12 KSP Residual norm 2.976158755617e-06
> > 14 KSP Residual norm 2.976038363683e-06
> > 16 KSP Residual norm 2.976102606899e-06
> > 18 KSP Residual norm 2.976429345213e-06
> > Linear solve did not converge due to DIVERGED_ITS iterations 18
> >
> > The solution diverges! The residual is 2.976429e-06. Solve again using
> GMRES!
> > 0 KSP Residual norm 4.932103470452e+00
> > 1 KSP Residual norm 4.586081825060e-01
> > 2 KSP Residual norm 4.702606826126e-02
> > 3 KSP Residual norm 5.717152414461e-03
> > 4 KSP Residual norm 5.122354290806e-04
> > 5 KSP Residual norm 4.682702445806e-05
> > 6 KSP Residual norm 4.368929895884e-06
> > 7 KSP Residual norm 4.908451624092e-07
> > 8 KSP Residual norm 4.758895647974e-08
> > 9 KSP Residual norm 3.831683374269e-09
> > 10 KSP Residual norm 2.844848230467e-10
> > 11 KSP Residual norm 2.252748969152e-11
> > 12 KSP Residual norm 1.432700892770e-12
> > 13 KSP Residual norm 9.569163228927e-14
> > 14 KSP Residual norm 1.129667714748e-14
> > Linear solve converged due to CONVERGED_RTOL iterations 14
> >
> > In poisson_func(): num_iter = 14, rel_residual = 1.129668e-14
> >
> > for my REFINE grid:
> >
> > imin = 4 imax = 28
> > jmin = 4 jmax = 10
> > kmin = 4 kmax = 28
> > KSP Object: 96 MPI processes
> > type not yet set
> > maximum iterations=20, initial guess is zero
> > tolerances: relative=1e-05, absolute=1e-50, divergence=10000
> > left preconditioning
> > using DEFAULT norm type for convergence test
> > PC Object: 96 MPI processes
> > type not yet set
> > PC has not been set up so information may be incomplete
> > KSP Object: 96 MPI processes
> > type not yet set
> > maximum iterations=20, initial guess is zero
> > tolerances: relative=1e-14, absolute=1e-50, divergence=10000
> > left preconditioning
> > using DEFAULT norm type for convergence test
> > PC Object: 96 MPI processes
> > type not yet set
> > PC has not been set up so information may be incomplete
> >
> > On Sun, Sep 17, 2017 at 1:22 AM, Hao Zhang <hbcbh1999 at gmail.com> wrote:
> > Thanks!
> >
> > On Sun, Sep 17, 2017 at 1:20 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> >
> > > On Sep 17, 2017, at 12:17 AM, Hao Zhang <hbcbh1999 at gmail.com> wrote:
> > >
> > > OK. I will check the output Calling KSPView()
> > >
> > > I am experimenting with -start_in_debugger. it's for serial not for
> parallel, right?
> >
> > It can be for parallel, opens an xterm with the debugger for each MPI
> process. You need to type cont in all the windows
> >
> >
> > >
> > > On Sun, Sep 17, 2017 at 1:12 AM, Barry Smith <bsmith at mcs.anl.gov>
> wrote:
> > >
> > > Should work in the code also. Call KSPSetTolerances() and then call
> KSPView() to see what it is set to
> > >
> > > > On Sep 17, 2017, at 12:11 AM, Hao Zhang <hbcbh1999 at gmail.com> wrote:
> > > >
> > > > Yes. but only works via command line option.before was set up in the
> code.
> > > >
> > > > On Sun, Sep 17, 2017 at 12:44 AM, Barry Smith <bsmith at mcs.anl.gov>
> wrote:
> > > >
> > > > > On Sep 16, 2017, at 11:33 PM, Hao Zhang <hbcbh1999 at gmail.com>
> wrote:
> > > > >
> > > > > thanks.
> > > > >
> > > > > Yes. KSPSetTolerances is used.
> > > > >
> > > > > tolerance is set to be 1.e-14
> > > >
> > > > There is the rtol and atol are you sure you set the atol to 1e-14?
> > > >
> > > > >
> > > > > I was thinking if there is a debug option I could use from PETSc
> to get some insight? GDB was used.
> > > >
> > > > You can use the command line option -start_in_debugger
> > > >
> > > >
> > > > >
> > > > > On Sun, Sep 17, 2017 at 12:25 AM, Barry Smith <bsmith at mcs.anl.gov>
> wrote:
> > > > >
> > > > > > On Sep 16, 2017, at 10:39 PM, Hao Zhang <hbcbh1999 at gmail.com>
> wrote:
> > > > > >
> > > > > > hi,
> > > > > >
> > > > > > I am using KSPBCGSL method and HYPRE boomeramg precondtioner
> passed into KSPsolve for poisson equation as part of incompressible NS.
> > > > > >
> > > > > > I have two questions
> > > > > > Q1 is number of iterations for the same solver. max_iter = 20
> for the same poisson function
> > > > > >
> > > > > > KSPGetIterationNumber() is used to set up max_iter = 20
> > > > >
> > > > > What do you mean, KSPGetIterationNumber() tells you the current
> number of iterations. You cannot use it to set the maximum number of
> iterations. Use KSPSetTolerances() or -ksp_max_it <its> to set the number
> > > > > >
> > > > > >
> > > > > > 0 KSP Residual norm 4.512245447770e-04
> > > > > > 2 KSP Residual norm 6.396709069731e-07
> > > > > > 4 KSP Residual norm 1.757784220489e-10
> > > > > > 6 KSP Residual norm 1.501464709144e-14
> > > > > > 8 KSP Residual norm 1.376381429122e-18
> > > > > > 10 KSP Residual norm 1.072650548945e-19
> > > > > > In poisson_func(): num_iter = 10, rel_residual = 1.072651e-19
> > > > > >
> > > > > > and the very same function at the next time step gives: remind
> you guys max_iter = 20. I assume the number of iterations should stop at
> num_iter = 2.
> > > > >
> > > > > Why would it stop at num_iter 2. The number of iterations
> allowed is the same for each solve, it does not accumulate over all solves.
> > > > >
> > > > > > but the solver seems to keep iterating util hitting the
> max_iter.
> > > > > > 0 KSP Residual norm 5.107005838093e-16
> > > > > > 2 KSP Residual norm 3.353634821198e-20
> > > > > > 4 KSP Residual norm 1.835096039266e-23
> > > > > > 6 KSP Residual norm 1.645496102409e-23
> > > > > > 8 KSP Residual norm 1.645496099837e-23
> > > > > > 10 KSP Residual norm 1.645496099836e-23
> > > > > > 12 KSP Residual norm 1.645496099530e-23
> > > > > > 14 KSP Residual norm 1.645496034473e-23
> > > > > > 16 KSP Residual norm 1.645461130961e-23
> > > > > > 18 KSP Residual norm 1.645460451075e-23
> > > > > > In poisson_func(): num_iter = 18, rel_residual = 1.645460e-23
> > > > >
> > > > > But the way it is almost never realistic to try to get residual
> norms to be this small. You might consider using something like -ksp_atol
> 1.e-16 or something
> > > > >
> > > > > >
> > > > > > Q2 is: it seems HYPRE with KSPsolve works with coarse mesh but
> when I double the mesh size. the solve halted indefinitely. ksp_monitor
> didn't produce any results.
> > > > > > is there a way to understand what's happening?
> > > > >
> > > > > You could run in the debugger and use control c to interrupt
> the code when it is "hanging" and type bt to see the stack trace for the
> hanging.
> > > > >
> > > > >
> > > > > >
> > > > > > --
> > > > > > Hao Zhang
> > > > > > Dept. of Applid Mathematics and Statistics,
> > > > > > Stony Brook University,
> > > > > > Stony Brook, New York, 11790
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > --
> > > > > Hao Zhang
> > > > > Dept. of Applid Mathematics and Statistics,
> > > > > Stony Brook University,
> > > > > Stony Brook, New York, 11790
> > > >
> > > >
> > > >
> > > >
> > > > --
> > > > Hao Zhang
> > > > Dept. of Applid Mathematics and Statistics,
> > > > Stony Brook University,
> > > > Stony Brook, New York, 11790
> > >
> > >
> > >
> > >
> > > --
> > > Hao Zhang
> > > Dept. of Applid Mathematics and Statistics,
> > > Stony Brook University,
> > > Stony Brook, New York, 11790
> >
> >
> >
> >
> > --
> > Hao Zhang
> > Dept. of Applid Mathematics and Statistics,
> > Stony Brook University,
> > Stony Brook, New York, 11790
> >
> >
> >
> > --
> > Hao Zhang
> > Dept. of Applid Mathematics and Statistics,
> > Stony Brook University,
> > Stony Brook, New York, 11790
>
>
--
Hao Zhang
Dept. of Applid Mathematics and Statistics,
Stony Brook University,
Stony Brook, New York, 11790
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