On Thu, Jan 21, 2021 at 1:44 PM Matthew Knepley <[email protected]> wrote:
> On Thu, Jan 21, 2021 at 11:16 AM Mark Adams <[email protected]> wrote: > >> Yes, the problem is that each KSP solver is running in an OMP thread (So >> at this point it only works for SELF and its Landau so it is all I need). >> It looks like MPI reductions called with a comm_self are not thread safe >> (eg, the could say, this is one proc, thus, just copy send --> recv, but >> they don't) >> > > Instead of using SELF, how about Comm_dup() for each thread? > OK, raw MPI_Comm_dup. I tried PetscCommDup. Let me this. Thanks, > > Matt > > >> On Thu, Jan 21, 2021 at 10:46 AM Matthew Knepley <[email protected]> >> wrote: >> >>> On Thu, Jan 21, 2021 at 10:34 AM Mark Adams <[email protected]> wrote: >>> >>>> It looks like PETSc is just too clever for me. I am trying to get a >>>> different MPI_Comm into each block, but PETSc is thwarting me: >>>> >>> >>> It looks like you are using SELF. Is that what you want? Do you want a >>> bunch of comms with the same group, but independent somehow? I am confused. >>> >>> Matt >>> >>> >>>> if (jac->use_openmp) { >>>> ierr = KSPCreate(MPI_COMM_SELF,&ilink->ksp);CHKERRQ(ierr); >>>> PetscPrintf(PETSC_COMM_SELF,"In PCFieldSplitSetFields_FieldSplit with >>>> -------------- link: %p. Comms %p >>>> %p\n",ilink,PetscObjectComm((PetscObject)pc),PetscObjectComm((PetscObject)ilink->ksp)); >>>> } else { >>>> ierr = >>>> KSPCreate(PetscObjectComm((PetscObject)pc),&ilink->ksp);CHKERRQ(ierr); >>>> } >>>> >>>> produces: >>>> >>>> In PCFieldSplitSetFields_FieldSplit with -------------- link: >>>> 0x7e9cb4f0. Comms 0x660c6ad0 0x660c6ad0 >>>> In PCFieldSplitSetFields_FieldSplit with -------------- link: >>>> 0x7e88f7d0. Comms 0x660c6ad0 0x660c6ad0 >>>> >>>> How can I work around this? >>>> >>>> >>>> On Thu, Jan 21, 2021 at 7:41 AM Mark Adams <[email protected]> wrote: >>>> >>>>> >>>>> >>>>> On Wed, Jan 20, 2021 at 6:21 PM Barry Smith <[email protected]> wrote: >>>>> >>>>>> >>>>>> >>>>>> On Jan 20, 2021, at 3:09 PM, Mark Adams <[email protected]> wrote: >>>>>> >>>>>> So I put in a temporary hack to get the first Fieldsplit apply to NOT >>>>>> use OMP and it sort of works. >>>>>> >>>>>> Preonly/lu is fine. GMRES calls vector creates/dups in every solve so >>>>>> that is a big problem. >>>>>> >>>>>> >>>>>> It should definitely not be creating vectors "in every" solve. But >>>>>> it does do lazy allocation of needed restarted vectors which may make it >>>>>> look like it is creating "every" vectors in every solve. You can >>>>>> use -ksp_gmres_preallocate to force it to create all the restart vectors >>>>>> up >>>>>> front at KSPSetUp(). >>>>>> >>>>> >>>>> Well, I run the first solve w/o OMP and I see Vec dups in cuSparse >>>>> Vecs in the 2nd solve. >>>>> >>>>> >>>>>> >>>>>> Why is creating vectors "at every solve" a problem? It is not >>>>>> thread safe I guess? >>>>>> >>>>> >>>>> It dies when it looks at the options database, in a Free in the >>>>> get-options method to be exact (see stacks). >>>>> >>>>> ======= Backtrace: ========= >>>>> /lib64/libc.so.6(cfree+0x4a0)[0x200021839be0] >>>>> >>>>> /gpfs/alpine/csc314/scratch/adams/petsc/arch-summit-opt-gnu-cuda-omp/lib/libpetsc.so.3.014(PetscFreeAlign+0x4c)[0x2000002a368c] >>>>> >>>>> /gpfs/alpine/csc314/scratch/adams/petsc/arch-summit-opt-gnu-cuda-omp/lib/libpetsc.so.3.014(PetscOptionsEnd_Private+0xf4)[0x2000002e53f0] >>>>> >>>>> /gpfs/alpine/csc314/scratch/adams/petsc/arch-summit-opt-gnu-cuda-omp/lib/libpetsc.so.3.014(+0x7c6c28)[0x2000008b6c28] >>>>> >>>>> /gpfs/alpine/csc314/scratch/adams/petsc/arch-summit-opt-gnu-cuda-omp/lib/libpetsc.so.3.014(VecCreate_SeqCUDA+0x11c)[0x20000052c510] >>>>> >>>>> /gpfs/alpine/csc314/scratch/adams/petsc/arch-summit-opt-gnu-cuda-omp/lib/libpetsc.so.3.014(VecSetType+0x670)[0x200000549664] >>>>> >>>>> /gpfs/alpine/csc314/scratch/adams/petsc/arch-summit-opt-gnu-cuda-omp/lib/libpetsc.so.3.014(VecCreateSeqCUDA+0x150)[0x20000052c0b0] >>>>> >>>>> /gpfs/alpine/csc314/scratch/adams/petsc/arch-summit-opt-gnu-cuda-omp/lib/libpetsc.so.3.014(+0x43c198)[0x20000052c198] >>>>> >>>>> /gpfs/alpine/csc314/scratch/adams/petsc/arch-summit-opt-gnu-cuda-omp/lib/libpetsc.so.3.014(VecDuplicate+0x44)[0x200000542168] >>>>> >>>>> /gpfs/alpine/csc314/scratch/adams/petsc/arch-summit-opt-gnu-cuda-omp/lib/libpetsc.so.3.014(VecDuplicateVecs_Default+0x148)[0x200000543820] >>>>> >>>>> /gpfs/alpine/csc314/scratch/adams/petsc/arch-summit-opt-gnu-cuda-omp/lib/libpetsc.so.3.014(VecDuplicateVecs+0x54)[0x2000005425f4] >>>>> >>>>> /gpfs/alpine/csc314/scratch/adams/petsc/arch-summit-opt-gnu-cuda-omp/lib/libpetsc.so.3.014(KSPCreateVecs+0x4b4)[0x2000016f0aec] >>>>> >>>>> >>>>> >>>>>> >>>>>> Richardson works except the convergence test gets confused, >>>>>> presumably because MPI reductions with PETSC_COMM_SELF is not threadsafe. >>>>>> >>>>>> >>>>>> >>>>>> One fix for the norms might be to create each subdomain solver with a >>>>>> different communicator. >>>>>> >>>>>> >>>>>> Yes you could do that. It might actually be the correct thing to >>>>>> do also, if you have multiple threads call MPI reductions on the same >>>>>> communicator that would be a problem. Each KSP should get a new MPI_Comm. >>>>>> >>>>> >>>>> OK. I will only do this. >>>>> >>>>> >>> >>> -- >>> What most experimenters take for granted before they begin their >>> experiments is infinitely more interesting than any results to which their >>> experiments lead. >>> -- Norbert Wiener >>> >>> https://www.cse.buffalo.edu/~knepley/ >>> <http://www.cse.buffalo.edu/~knepley/> >>> >> > > -- > What most experimenters take for granted before they begin their > experiments is infinitely more interesting than any results to which their > experiments lead. > -- Norbert Wiener > > https://www.cse.buffalo.edu/~knepley/ > <http://www.cse.buffalo.edu/~knepley/> >
