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? 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/>
