Hey,
On 13 February 2017 at 19:41, Barry Smith <[email protected]> wrote: > > From the manual page: KSPSetComputeOperators() is not propagated to the > sub KSP. > Hmm - it does indeed say that. The statement is partially correct. If a DM is not attached to the KSP, the computeoperators method is NOT propagated. If a DM is attached, is in fact propagated, see telescope_dmda.c : 502 As usual the doc lags behind the implementation :( [my fault] > > Yet there is some code > sred->ignore_kspcomputeoperators = PETSC_FALSE; > if (sred->ignore_kspcomputeoperators) { > ierr = PetscViewerASCIIPrintf(subviewer," Telescope: ignoring > KSPComputeOperators\n");CHKERRQ(ierr); > } > ierr = PetscOptionsBool("-pc_telescope_ignore_kspcomputeoperators","Ignore > method used to compute A","PCTelescopeSetIgnoreKSPCom > puteOperators",sred->ignore_kspcomputeoperators,&sred->ignor > e_kspcomputeoperators,0);CHKERRQ(ierr); > etc > > that seems to indicate that Dave May intended to have support for > KSPComputeOperator ... but didn't complete it. > True - I didn't try this implementation out with any SNES examples. Note it is/was tested and to my knowledge does work for linear cases. Hopefully someone can confirm/deny this. I should also note that it was already fragile for the linear only case. For instance if the computeoperators function employed a matrix-free method which involved some stored data (e.g. viscosity on a quadrature point), then the user would have to cleverly (e.g. via a hack) also communicate said quadrature values from the parent comm to the sub-comm. I never found a clean way to manage this operation. > In this case it is using KSPComputeOperators_SNES(KSP ksp,Mat A,Mat > B,void *ctx); which needs a couple of things changed to get it to work: > > 1) KSPComputeOperators_SNES() needs to work when the subdm is on a smaller > set of processes so the call to SNESComputeJacobian() has to handle running > on a subset of process (which of course it cannot do normally because the > SNES has its full communicator while the DM only lives on a subset of > processes). > The motivating idea behind adding support for setcomputeoperators was to (i) avoid having to permute an assembled operator defined on the parent comm, into the ordering on the sub-comm and (ii) to permit people to use a matrix-free implementation. The SNES case, at least with an assembled jacobian, should be possible to make work. We would assemble J on the parent comm, then we can move the operator on the sub-comm and do what we like. Does that sound reasonable? > > 2) The DMRestrictHook_SNESVecSol() has to handle switching to a DM on a > smaller set of processes and remapping the "solution" vector to that > smaller set. > Hmmm - that seems awkward. Sounds like the user will have to do something magical in their hook definition... > > Dave and Jed, > > All and all looks awfully complex and fragile to get this working. > What do you think? > > Barry > > Curse whoever designed PETSc originally and didn't take into account in > its basic design the need to subcom PETSc objects to smaller communicators > :-( > LOL. Cheers, Dave > > > > On Feb 13, 2017, at 10:01 AM, Zhang, Hong <[email protected]> wrote: > > > > Hi Barry, > > > > When using telescope, I get an error complaining about missing Jacobian. > But apparently I have a Jacobian set by TSSetIJacobian(). > > > > [0]PETSC ERROR: --------------------- Error Message > -------------------------------------------------------------- > > [0]PETSC ERROR: > > [0]PETSC ERROR: Must call SNESSetJacobian(), DMSNESSetJacobian(), > DMDASNESSetJacobianLocal(), etc > > [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html > for trouble shooting. > > [0]PETSC ERROR: Petsc Development GIT revision: v3.7.4-2764-g0ff3c95 > GIT Date: 2017-01-10 15:40:21 -0600 > > [0]PETSC ERROR: ./ex5adj_ell on a arch-memalign-mkl-avx512-opt named > isdp001.cels.anl.gov by hongzh Mon Feb 13 09:56:48 2017 > > [0]PETSC ERROR: Configure options --COPTFLAGS="-g -O3 -xMIC-AVX512" > --CXXOPTFLAGS="-g -O3 -xMIC-AVX512" --FOPTFLAGS="-g -O3 -xMIC-AVX512" > --PETSC_ARCH=arch-memalign-mkl-avx512-opt > --PETSC_DIR=/homes/hongzh/Projects/petsc > --download-cmake --download-revolve=1 --with-blaslapack-dir=/opt/int > el/2017-initial/compilers_and_libraries_2017/linux/mkl/lib/intel64 > --with-cc=mpiicc --with-cxx=mpiicpc --with-debugging=no --with-fc=mpiifort > --with-memalign=64 --with-mpiexec=mpirun > > [0]PETSC ERROR: #1 SNESComputeJacobian() line 2242 in > /home/hongzh/Projects/petsc/src/snes/interface/snes.c > > [0]PETSC ERROR: #2 KSPComputeOperators_SNES() line 569 in > /home/hongzh/Projects/petsc/src/snes/interface/snes.c > > [0]PETSC ERROR: #3 KSPSetUp() line 327 in /home/hongzh/Projects/petsc/sr > c/ksp/ksp/interface/itfunc.c > > [0]PETSC ERROR: #4 KSPSolve() line 599 in /home/hongzh/Projects/petsc/sr > c/ksp/ksp/interface/itfunc.c > > [0]PETSC ERROR: #5 PCApply_Telescope_dmda() line 952 in > /home/hongzh/Projects/petsc/src/ksp/pc/impls/telescope/telescope_dmda.c > > [0]PETSC ERROR: #6 PCApply() line 458 in /home/hongzh/Projects/petsc/sr > c/ksp/pc/interface/precon.c > > [0]PETSC ERROR: #7 KSP_PCApply() line 251 in > /homes/hongzh/Projects/petsc/include/petsc/private/kspimpl.h > > [0]PETSC ERROR: #8 KSPSolve_PREONLY() line 22 in > /home/hongzh/Projects/petsc/src/ksp/ksp/impls/preonly/preonly.c > > [0]PETSC ERROR: #9 KSPSolve() line 656 in /home/hongzh/Projects/petsc/sr > c/ksp/ksp/interface/itfunc.c > > [0]PETSC ERROR: #10 PCMGMCycle_Private() line 19 in > /home/hongzh/Projects/petsc/src/ksp/pc/impls/mg/mg.c > > [0]PETSC ERROR: #11 PCMGMCycle_Private() line 53 in > /home/hongzh/Projects/petsc/src/ksp/pc/impls/mg/mg.c > > [0]PETSC ERROR: #12 PCMGMCycle_Private() line 53 in > /home/hongzh/Projects/petsc/src/ksp/pc/impls/mg/mg.c > > [0]PETSC ERROR: #13 PCMGMCycle_Private() line 53 in > /home/hongzh/Projects/petsc/src/ksp/pc/impls/mg/mg.c > > [0]PETSC ERROR: #14 PCMGMCycle_Private() line 53 in > /home/hongzh/Projects/petsc/src/ksp/pc/impls/mg/mg.c > > [0]PETSC ERROR: #15 PCApply_MG() line 331 in > /home/hongzh/Projects/petsc/src/ksp/pc/impls/mg/mg.c > > [0]PETSC ERROR: #16 PCApply() line 458 in /home/hongzh/Projects/petsc/sr > c/ksp/pc/interface/precon.c > > [0]PETSC ERROR: #17 KSP_PCApply() line 251 in > /homes/hongzh/Projects/petsc/include/petsc/private/kspimpl.h > > [0]PETSC ERROR: #18 KSPInitialResidual() line 67 in > /home/hongzh/Projects/petsc/src/ksp/ksp/interface/itres.c > > [0]PETSC ERROR: #19 KSPSolve_GMRES() line 233 in > /home/hongzh/Projects/petsc/src/ksp/ksp/impls/gmres/gmres.c > > [0]PETSC ERROR: #20 KSPSolve() line 656 in /home/hongzh/Projects/petsc/sr > c/ksp/ksp/interface/itfunc.c > > [0]PETSC ERROR: #21 SNESSolve_NEWTONLS() line 224 in > /home/hongzh/Projects/petsc/src/snes/impls/ls/ls.c > > [0]PETSC ERROR: #22 SNESSolve() line 3967 in > /home/hongzh/Projects/petsc/src/snes/interface/snes.c > > [0]PETSC ERROR: #23 TS_SNESSolve() line 171 in > /home/hongzh/Projects/petsc/src/ts/impls/implicit/theta/theta.c > > [0]PETSC ERROR: #24 TSStep_Theta() line 211 in > /home/hongzh/Projects/petsc/src/ts/impls/implicit/theta/theta.c > > [0]PETSC ERROR: #25 TSStep() line 3808 in /home/hongzh/Projects/petsc/sr > c/ts/interface/ts.c > > [0]PETSC ERROR: #26 TSSolve() line 4053 in /home/hongzh/Projects/petsc/sr > c/ts/interface/ts.c > > [0]PETSC ERROR: #27 main() line 171 in /homes/hongzh/Projects/petsc/s > rc/ts/examples/tutorials/advection-diffusion-reaction/ex5adj_ell.c > > [0]PETSC ERROR: PETSc Option Table entries: > > [0]PETSC ERROR: -da_refine 4 > > [0]PETSC ERROR: -dm_mat_type aij > > [0]PETSC ERROR: -forwardonly > > [0]PETSC ERROR: -ksp_converged_reason > > [0]PETSC ERROR: -ksp_view > > [0]PETSC ERROR: -mg_coarse_pc_telescope_reduction_factor 2 > > [0]PETSC ERROR: -mg_coarse_pc_type telescope > > [0]PETSC ERROR: -mg_coarse_telescope_pc_type lu > > [0]PETSC ERROR: -mg_levels_pc_type jacobi > > [0]PETSC ERROR: -pc_type mg > > [0]PETSC ERROR: -ts_dt 1 > > [0]PETSC ERROR: -ts_max_steps 1 > > [0]PETSC ERROR: ----------------End of Error Message -------send entire > error message to [email protected] > > > > Thanks, > > Hong > >
