[petsc-users] KSP_CONVERGED_STEP_LENGTH
Harshad Sahasrabudhe
hsahasra at purdue.edu
Wed Sep 14 14:09:00 CDT 2016
Hi Barry,
Sorry, I had no idea that Newton TR would have anything to do with the
linear solver. I was using TR because it is trustworthy and converges every
time. I tried LS just now with GAMG+GMRES and it converges, so I don't have
the CONVERGED_STEP_LENGTH problem anymore.
Thanks for you help!
Harshad
On Wed, Sep 14, 2016 at 2:51 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
> Oh, you are using SNESSolve_NEWTONTR !
>
> Now it all makes sense! The trust region methods impose other
> conditions on the linear solution so it needs to have their own special
> convergence test. In particular it requires that the solution from the
> linear solve be inside the trust region (i.e. not too big)
>
> So, any particular reason you use SNESSolve_NEWTONTR instead of the
> default line search NEWTONLS? In general unless you have a good reason I
> recommend just using the NEWTONLS.
>
> If you really want to use the TR then the "early" return from the
> linear solve is expected, it is controlled by the trust region size and is
> not under user control.
>
> I'm sorry I was so brain dead and did not realize you had be using TR
> or we could have resolved this much sooner.
>
> Barry
>
>
>
> > On Sep 14, 2016, at 1:31 PM, Harshad Sahasrabudhe <hsahasra at purdue.edu>
> wrote:
> >
> > Thanks. I now put a watchpoint on
> >
> > watch *( (PetscErrorCode (**)(KSP, PetscInt, PetscReal,
> KSPConvergedReason *, void *)) &(ksp->converged) )
> >
> > The function pointer changes in the first iteration of SNES. It changed
> at the following place:
> >
> > Old value =
> > (PetscErrorCode (*)(KSP, PetscInt, PetscReal, KSPConvergedReason *,
> void *)) 0x2b54acdd00aa <KSPConvergedDefault(KSP, PetscInt, PetscReal,
> KSPConvergedReason*, void*)>
> > New value =
> > (PetscErrorCode (*)(KSP, PetscInt, PetscReal, KSPConvergedReason *,
> void *)) 0x2b54ad436ce8 <.SNES_TR_KSPConverged_
> Private.SNES_TR_KSPConverged_Private.SNES_TR_KSPConverged_Private(_p_KSP*,
> int, double, KSPConvergedReason*, void*)>
> > KSPSetConvergenceTest (ksp=0x22bf090, converge=0x2b54ad436ce8
> <SNES_TR_KSPConverged_Private(_p_KSP*, int, double, KSPConvergedReason*,
> void*)>, cctx=0x1c8b3e0,
> > destroy=0x2b54ad437210 <SNES_TR_KSPConverged_Destroy(void*)>)
> > at /depot/ncn/apps/conte/conte-gcc-petsc35-dbg/libs/petsc/
> build-real/src/ksp/ksp/interface/itfunc.c:1768
> > 1767 ksp->converged = converge;
> >
> > Here's the backtrace:
> >
> > #0 KSPSetConvergenceTest (ksp=0x22bf090, converge=0x2b54ad436ce8
> <SNES_TR_KSPConverged_Private(_p_KSP*, int, double, KSPConvergedReason*,
> void*)>, cctx=0x1c8b3e0,
> > destroy=0x2b54ad437210 <SNES_TR_KSPConverged_Destroy(void*)>)
> > at /depot/ncn/apps/conte/conte-gcc-petsc35-dbg/libs/petsc/
> build-real/src/ksp/ksp/interface/itfunc.c:1768
> > #1 0x00002b54ad43865a in SNESSolve_NEWTONTR (snes=0x1d9e490) at
> /depot/ncn/apps/conte/conte-gcc-petsc35-dbg/libs/petsc/
> build-real/src/snes/impls/tr/tr.c:146
> > #2 0x00002b54acedab57 in SNESSolve (snes=0x1d9e490, b=0x0, x=0x1923420)
> > at /depot/ncn/apps/conte/conte-gcc-petsc35-dbg/libs/petsc/
> build-real/src/snes/interface/snes.c:3743
> > #3 0x00002b54abe8b780 in libMesh::PetscNonlinearSolver<double>::solve
> (this=0x19198c0, jac_in=..., x_in=..., r_in=...) at
> src/solvers/petsc_nonlinear_solver.C:714
> > #4 0x00002b54abefa61d in libMesh::NonlinearImplicitSystem::solve
> (this=0x1910fe0) at src/systems/nonlinear_implicit_system.C:183
> > #5 0x00002b54a5dcdceb in NonlinearPoisson::execute_solver
> (this=0x100c500) at NonlinearPoisson.cpp:1191
> > #6 0x00002b54a5da733c in NonlinearPoisson::do_solve (this=0x100c500) at
> NonlinearPoisson.cpp:948
> > #7 0x00002b54a6423785 in Simulation::solve (this=0x100c500) at
> Simulation.cpp:781
> > #8 0x00002b54a634826e in Nemo::run_simulations (this=0x63b020) at
> Nemo.cpp:1313
> > #9 0x0000000000426d0d in main (argc=6, argv=0x7ffcdb910768) at
> main.cpp:447
> >
> > Thanks,
> > Harshad
> >
> >
> > On Wed, Sep 14, 2016 at 2:07 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> >
> > Super strange, it should never have switched to the function
> SNES_TR_KSPConverged_Private
> >
> > Fortunately you can use the same technique to track down where the
> function pointer changes. Just watch ksp->converged to see when the
> function pointer gets changed and send back the new stack trace.
> >
> > Barry
> >
> >
> >
> >
> > > On Sep 14, 2016, at 12:39 PM, Harshad Sahasrabudhe <
> hsahasra at purdue.edu> wrote:
> > >
> > > Hi Barry,
> > >
> > > I put a watchpoint on *((KSP_CONVERGED_REASON*) &(
> ((_p_KSP*)ksp)->reason )) in gdb. The ksp->reason switched between:
> > >
> > > Old value = KSP_CONVERGED_ITERATING
> > > New value = KSP_CONVERGED_RTOL
> > > 0x00002b143054bef2 in KSPConvergedDefault (ksp=0x23c3090, n=12,
> rnorm=5.3617149831259514e-08, reason=0x23c3310, ctx=0x2446210)
> > > at /depot/ncn/apps/conte/conte-gcc-petsc35-dbg/libs/petsc/
> build-real/src/ksp/ksp/interface/iterativ.c:764
> > > 764 *reason = KSP_CONVERGED_RTOL;
> > >
> > > and
> > >
> > > Old value = KSP_CONVERGED_RTOL
> > > New value = KSP_CONVERGED_ITERATING
> > > KSPSetUp (ksp=0x23c3090) at /depot/ncn/apps/conte/conte-
> gcc-petsc35-dbg/libs/petsc/build-real/src/ksp/ksp/interface/itfunc.c:226
> > > 226 if (!((PetscObject)ksp)->type_name) {
> > >
> > > However, after iteration 6, it changed to KSP_CONVERGED_STEP_LENGTH
> > >
> > > Old value = KSP_CONVERGED_ITERATING
> > > New value = KSP_CONVERGED_STEP_LENGTH
> > > SNES_TR_KSPConverged_Private (ksp=0x23c3090, n=1,
> rnorm=0.097733468578376406, reason=0x23c3310, cctx=0x1d8f3e0)
> > > at /depot/ncn/apps/conte/conte-gcc-petsc35-dbg/libs/petsc/
> build-real/src/snes/impls/tr/tr.c:36
> > > 36 PetscFunctionReturn(0);
> > >
> > > Any ideas why that function was executed? Backtrace when the program
> stopped here:
> > >
> > > #0 SNES_TR_KSPConverged_Private (ksp=0x23c3090, n=1,
> rnorm=0.097733468578376406, reason=0x23c3310, cctx=0x1d8f3e0)
> > > at /depot/ncn/apps/conte/conte-gcc-petsc35-dbg/libs/petsc/
> build-real/src/snes/impls/tr/tr.c:36
> > > #1 0x00002b14305d3fda in KSPGMRESCycle (itcount=0x7ffdcf2d4ffc,
> ksp=0x23c3090)
> > > at /depot/ncn/apps/conte/conte-gcc-petsc35-dbg/libs/petsc/
> build-real/src/ksp/ksp/impls/gmres/gmres.c:182
> > > #2 0x00002b14305d4711 in KSPSolve_GMRES (ksp=0x23c3090) at
> /depot/ncn/apps/conte/conte-gcc-petsc35-dbg/libs/petsc/
> build-real/src/ksp/ksp/impls/gmres/gmres.c:235
> > > #3 0x00002b1430526a8a in KSPSolve (ksp=0x23c3090, b=0x1a916c0,
> x=0x1d89dc0)
> > > at /depot/ncn/apps/conte/conte-gcc-petsc35-dbg/libs/petsc/
> build-real/src/ksp/ksp/interface/itfunc.c:460
> > > #4 0x00002b1430bb3905 in SNESSolve_NEWTONTR (snes=0x1ea2490) at
> /depot/ncn/apps/conte/conte-gcc-petsc35-dbg/libs/petsc/
> build-real/src/snes/impls/tr/tr.c:160
> > > #5 0x00002b1430655b57 in SNESSolve (snes=0x1ea2490, b=0x0,
> x=0x1a27420)
> > > at /depot/ncn/apps/conte/conte-gcc-petsc35-dbg/libs/petsc/
> build-real/src/snes/interface/snes.c:3743
> > > #6 0x00002b142f606780 in libMesh::PetscNonlinearSolver<double>::solve
> (this=0x1a1d8c0, jac_in=..., x_in=..., r_in=...) at
> src/solvers/petsc_nonlinear_solver.C:714
> > > #7 0x00002b142f67561d in libMesh::NonlinearImplicitSystem::solve
> (this=0x1a14fe0) at src/systems/nonlinear_implicit_system.C:183
> > > #8 0x00002b1429548ceb in NonlinearPoisson::execute_solver
> (this=0x1110500) at NonlinearPoisson.cpp:1191
> > > #9 0x00002b142952233c in NonlinearPoisson::do_solve (this=0x1110500)
> at NonlinearPoisson.cpp:948
> > > #10 0x00002b1429b9e785 in Simulation::solve (this=0x1110500) at
> Simulation.cpp:781
> > > #11 0x00002b1429ac326e in Nemo::run_simulations (this=0x63b020) at
> Nemo.cpp:1313
> > > #12 0x0000000000426d0d in main (argc=6, argv=0x7ffdcf2d7908) at
> main.cpp:447
> > >
> > >
> > > Thanks!
> > > Harshad
> > >
> > > On Wed, Sep 14, 2016 at 10:10 AM, Harshad Sahasrabudhe <
> hsahasra at purdue.edu> wrote:
> > > I think I found the problem. I configured PETSc with COPTFLAGS=-O3.
> I'll remove that option and try again.
> > >
> > > Thanks!
> > > Harshad
> > >
> > > On Wed, Sep 14, 2016 at 10:06 AM, Harshad Sahasrabudhe <
> hsahasra at purdue.edu> wrote:
> > > Hi Barry,
> > >
> > > Thanks for your inputs. I tried to set a watchpoint on
> ((_p_KSP*)ksp)->reason, but gdb says no symbol _p_KSP in context.
> Basically, GDB isn't able to find the PETSc source code. I built PETSc with
> --with-debugging=1 statically and -fPIC, but it seems the libpetsc.a I get
> doesn't contain debugging symbols (checked using objdump -g). How do I get
> PETSc library to have debugging info?
> > >
> > > Thanks,
> > > Harshad
> > >
> > > On Tue, Sep 13, 2016 at 2:47 PM, Barry Smith <bsmith at mcs.anl.gov>
> wrote:
> > >
> > > > On Sep 13, 2016, at 1:01 PM, Harshad Sahasrabudhe <
> hsahasra at purdue.edu> wrote:
> > > >
> > > > Hi Barry,
> > > >
> > > > I compiled with mpich configured using --enable-g=meminit to get rid
> of MPI errors in Valgrind. Doing this reduced the number of errors to 2. I
> have attached the Valgrind output.
> > >
> > > This isn't helpful but it seems not to be a memory corruption issue
> :-(
> > > >
> > > > I'm using GAMG+GMRES for in each linear iteration of SNES. The
> linear solver converges with CONVERGED_RTOL for the first 6 iterations and
> with CONVERGED_STEP_LENGTH after that. I'm still very confused about why
> this is happening. Any thoughts/ideas?
> > >
> > > Does this happen on one process? If so I would run in the debugger
> and track the variable to see everyplace the variable is changed, this
> would point to exactly what piece of code is changing the variable to this
> unexpected value.
> > >
> > > For example with lldb one can use watch
> http://lldb.llvm.org/tutorial.html to see each time a variable gets
> changed. Similar thing with gdb.
> > >
> > > The variable to watch is ksp->reason Once you get the hang of this
> it can take just a few minutes to track down the code that is making this
> unexpected value, though I understand if you haven't done it before it can
> be intimidating.
> > >
> > > Barry
> > >
> > > You can do the same thing in parallel (like on two processes) if you
> need to but it is more cumbersome since you need run multiple debuggers.
> You can have PETSc start up multiple debuggers with mpiexec -n 2 ./ex
> -start_in_debugger
> > >
> > >
> > >
> > >
> > > >
> > > > Thanks,
> > > > Harshad
> > > >
> > > > On Thu, Sep 8, 2016 at 11:26 PM, Barry Smith <bsmith at mcs.anl.gov>
> wrote:
> > > >
> > > > Install your MPI with --download-mpich as a PETSc ./configure
> option, this will eliminate all the MPICH valgrind errors. Then send as an
> attachment the resulting valgrind file.
> > > >
> > > > I do not 100 % trust any code that produces such valgrind errors.
> > > >
> > > > Barry
> > > >
> > > >
> > > >
> > > > > On Sep 8, 2016, at 10:12 PM, Harshad Sahasrabudhe <
> hsahasra at purdue.edu> wrote:
> > > > >
> > > > > Hi Barry,
> > > > >
> > > > > Thanks for the reply. My code is in C. I ran with Valgrind and
> found many "Conditional jump or move depends on uninitialized value(s)",
> "Invalid read" and "Use of uninitialized value" errors. I think all of them
> are from the libraries I'm using (LibMesh, Boost, MPI, etc.). I'm not
> really sure what I'm looking for in the Valgrind output. At the end of the
> file, I get:
> > > > >
> > > > > ==40223== More than 10000000 total errors detected. I'm not
> reporting any more.
> > > > > ==40223== Final error counts will be inaccurate. Go fix your
> program!
> > > > > ==40223== Rerun with --error-limit=no to disable this cutoff. Note
> > > > > ==40223== that errors may occur in your program without prior
> warning from
> > > > > ==40223== Valgrind, because errors are no longer being displayed.
> > > > >
> > > > > Can you give some suggestions on how I should proceed?
> > > > >
> > > > > Thanks,
> > > > > Harshad
> > > > >
> > > > > On Thu, Sep 8, 2016 at 1:59 PM, Barry Smith <bsmith at mcs.anl.gov>
> wrote:
> > > > >
> > > > > This is very odd. CONVERGED_STEP_LENGTH for KSP is very
> specialized and should never occur with GMRES.
> > > > >
> > > > > Can you run with valgrind to make sure there is no memory
> corruption? http://www.mcs.anl.gov/petsc/documentation/faq.html#valgrind
> > > > >
> > > > > Is your code fortran or C?
> > > > >
> > > > > Barry
> > > > >
> > > > > > On Sep 8, 2016, at 10:38 AM, Harshad Sahasrabudhe <
> hsahasra at purdue.edu> wrote:
> > > > > >
> > > > > > Hi,
> > > > > >
> > > > > > I'm using GAMG + GMRES for my Poisson problem. The solver
> converges with KSP_CONVERGED_STEP_LENGTH at a residual of
> 9.773346857844e-02, which is much higher than what I need (I need a
> tolerance of at least 1E-8). I am not able to figure out which tolerance I
> need to set to avoid convergence due to CONVERGED_STEP_LENGTH.
> > > > > >
> > > > > > Any help is appreciated! Output of -ksp_view and -ksp_monitor:
> > > > > >
> > > > > > 0 KSP Residual norm 3.121347818142e+00
> > > > > > 1 KSP Residual norm 9.773346857844e-02
> > > > > > Linear solve converged due to CONVERGED_STEP_LENGTH iterations
> 1
> > > > > > KSP Object: 1 MPI processes
> > > > > > type: gmres
> > > > > > GMRES: restart=30, using Classical (unmodified) Gram-Schmidt
> Orthogonalization with no iterative refinement
> > > > > > GMRES: happy breakdown tolerance 1e-30
> > > > > > maximum iterations=10000, initial guess is zero
> > > > > > tolerances: relative=1e-08, absolute=1e-50, divergence=10000
> > > > > > left preconditioning
> > > > > > using PRECONDITIONED norm type for convergence test
> > > > > > PC Object: 1 MPI processes
> > > > > > type: gamg
> > > > > > MG: type is MULTIPLICATIVE, levels=2 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: bjacobi
> > > > > > block Jacobi: number of blocks = 1
> > > > > > Local solve is same for all blocks, in the following KSP
> and PC objects:
> > > > > > KSP Object: (mg_coarse_sub_) 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_sub_) 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 5, needed 1.91048
> > > > > > Factored matrix follows:
> > > > > > Mat Object: 1 MPI processes
> > > > > > type: seqaij
> > > > > > rows=284, cols=284
> > > > > > package used to perform factorization: petsc
> > > > > > total: nonzeros=7726, allocated nonzeros=7726
> > > > > > total number of mallocs used during
> MatSetValues calls =0
> > > > > > using I-node routines: found 133 nodes,
> limit used is 5
> > > > > > linear system matrix = precond matrix:
> > > > > > Mat Object: 1 MPI processes
> > > > > > type: seqaij
> > > > > > rows=284, cols=284
> > > > > > total: nonzeros=4044, allocated nonzeros=4044
> > > > > > total number of mallocs used during MatSetValues
> calls =0
> > > > > > not using I-node routines
> > > > > > linear system matrix = precond matrix:
> > > > > > Mat Object: 1 MPI processes
> > > > > > type: seqaij
> > > > > > rows=284, cols=284
> > > > > > total: nonzeros=4044, allocated nonzeros=4044
> > > > > > 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: chebyshev
> > > > > > Chebyshev: eigenvalue estimates: min = 0.195339, max =
> 4.10212
> > > > > > 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=9036, cols=9036
> > > > > > total: nonzeros=192256, allocated nonzeros=192256
> > > > > > total number of mallocs used during MatSetValues calls =0
> > > > > > 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=9036, cols=9036
> > > > > > total: nonzeros=192256, allocated nonzeros=192256
> > > > > > total number of mallocs used during MatSetValues calls =0
> > > > > > not using I-node routines
> > > > > >
> > > > > > Thanks,
> > > > > > Harshad
> > > > >
> > > > >
> > > >
> > > >
> > > > <valgrind.log.33199>
> > >
> > >
> > >
> > >
> >
> >
>
>
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