> On Jan 20, 2017, at 7:01 PM, Matthew Knepley <[email protected]> wrote: > > On Fri, Jan 20, 2017 at 3:08 PM, Barry Smith <[email protected]> wrote: > > > On Jan 20, 2017, at 3:01 PM, Zhang, Hong <[email protected]> wrote: > > > > We set C->submat_singleis = false as default. > > User turns it on when he knows a single IS will be used for > > MatGetSubMatrices(), e.g., when asm is used. > > User should turn the flag off after it is being used. > > Right, this is why I am confused why this is messing up Mat since > presumably he is not setting it? > > ASM is turning this flag on, and it is corrupting my UNRELATED call to > MatGetSubMatrices().
Yes, but you need to tell us exactly how. The flag is set into C->submat_singleis which is associated with the C from ASM, so why is it affecting your UNRELATED call to MatGetSubMatrices(). It is not a global variable so shouldn't. Explain or send a code that reproduces the problem. Barry > > Matt > > > > > This flag is for optimization -- avoid MPI_Allreduce, which is expensive > > for np>10k. > > MatGetSubMatrices() works without this flag turns on. > > I just merged the improved MatGetSubMatrices_MPIAIJ() which only calls > > MPI_Allreduce once > > for repeated use. Previously, it calls MPI_Allreduce twice for each call of > > MatGetSubMatrices_MPIAIJ(). > > > > Hong > > > > ________________________________________ > > From: Barry Smith [[email protected]] > > Sent: Friday, January 20, 2017 1:11 PM > > To: Matthew Knepley > > Cc: Zhang, Hong; PETSc > > Subject: Re: [petsc-dev] Bug introduced in MatGetSubmatrices() > > > >> On Jan 20, 2017, at 12:45 PM, Matthew Knepley <[email protected]> wrote: > >> > >> On Fri, Jan 20, 2017 at 11:55 AM, Barry Smith <[email protected]> wrote: > >> > >>> On Jan 20, 2017, at 11:49 AM, Matthew Knepley <[email protected]> wrote: > >>> > >>> On Fri, Jan 20, 2017 at 10:49 AM, Hong <[email protected]> wrote: > >>> Matt, > >>> By default, the flag C->submat_singleis = false. > >>> In PCSetUp_ASM(), we set it as 'true' to use > >>> MatGetSubMatrices_MPIAIJ_SingleIS(). > >>> > >>> Can you check the value of this flag in your case? > >>> > >>> The problem is the following: > >>> > >>> 1) We use MatGetSubMatrices() to extract small matrices in order to form > >>> a preconditioner > >>> > >>> 2) We do this at each Newton iteration > >>> > >>> 3) We use ASM as a preconditioner for the eventual Newton solve > >>> > >>> 4) The second time we call MatGetSubMatrices(), it has this flag set, > >>> even though we are using multiple ISes > >>> > >>> Solution: ALSO check that the user is in fact passing a single IS. > >>> > >> This requires a communication. I am confused, is the number of IS > >> changing each time? If not why is the flag set? > >> > >> ASM sets this flag because it knows that IT is going to call > >> MatGetSubMatrices() later, but it unsafe if any user calls > >> MatGetSubMatrices() as well. I think overall its a fragile design and > >> should be scrapped. > > > > You mean the user calls the SAME MatGetSubMatrices with the same > > matrices, right? Not a completely different unrelated MatGetSubMatrices() > > which should not be affect by the previous unrelated call. > > > > > > Barry > > > >> > >> Matt > >> > >> > >> Barry > >> > >>> Matt > >>> > >>> Hong > >>> > >>> It comes from here: > >>> > >>> > >>> https://bitbucket.org/petsc/petsc/commits/c10200c1442b553b7ad65c70101560db4fa22e78 > >>> > >>> If we ask for more than 1 matrix, it dispatches to > >>> > >>> MatGetSubMatrices_MPIAIJ_SingleIS() > >>> > >>> but then fails here > >>> > >>> > >>> https://bitbucket.org/petsc/petsc/annotate/2e559809f9aee9c95ee79eb0939630cfe5502c8d/src/mat/impls/aij/mpi/mpiov.c?at=master&fileviewer=file-view-default#mpiov.c-1306 > >>> > >>> because ismax > 1. I think the ismax check needs to move up to here > >>> > >>> > >>> https://bitbucket.org/petsc/petsc/annotate/2e559809f9aee9c95ee79eb0939630cfe5502c8d/src/mat/impls/aij/mpi/mpiov.c?at=master&fileviewer=file-view-default#mpiov.c-2012 > >>> > >>> but I don't know for sure. Please fix this since it is breaking PyLith. > >>> > >>> Matt > >>> > >>> -- > >>> 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 > >>> > >>> > >>> > >>> > >>> > >>> -- > >>> 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 > >> > >> > >> > >> > >> -- > >> 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 > > > > > > > > > -- > 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
