Hong, as far as I can tell, none of these changes should be merged to petsc-dev right now. If you go through with the merge, use hg diff -r SHA1_OF_UPSTREAM_PETSC_DEV to make sure that none of this 3.3 stuff gets merged. Otherwise, one of us can do the merge.
On Tue, Aug 21, 2012 at 11:08 AM, Hong Zhang <hzhang at mcs.anl.gov> wrote: > Dmitry : > I pushed a bugfix of mumps interface to 3.3. When merging it to petsc-dev, > I get > > merging src/ksp/pc/impls/fieldsplit/fieldsplit.c failed! > > Hong > > >> >> On Mon, Aug 20, 2012 at 8:36 AM, Jed Brown <jedbrown at mcs.anl.gov> wrote: >> >>> On Mon, Aug 20, 2012 at 4:02 AM, Dmitry Karpeev <karpeev at >>> mcs.anl.gov>wrote: >>> >>>> >>>> >>>> On Sun, Aug 19, 2012 at 1:17 PM, Jed Brown <jedbrown at mcs.anl.gov>wrote: >>>> >>>>> On Sun, Aug 19, 2012 at 12:48 PM, Dmitry Karpeev <karpeev at >>>>> mcs.anl.gov>wrote: >>>>> >>>>>> The main reason for this being a patch in 3.3 is that recursive >>>>>> FieldSplit is broken there (which is why I couldn't enable it in >>>>>> libMesh/Moose correctly). >>>>> >>>>> >>>>> The current interface doesn't explicitly support all the ways to get >>>>> information into the split, but several people have worked around the >>>>> limitations to get the necessary information in there. Having you and Matt >>>>> changing things to rely on mutually incompatible side-effects does not >>>>> help. >>>>> >>>> I don't think the present fix is about the API or working through side >>>> effects (nullspace stuff excluded and partially backed out here: >>>> http://petsc.cs.iit.edu/petsc/releases/petsc-3.3/rev/1723d4624521) >>>> >>> >>> What do you call this external DM futzing? >>> >> It's no different than holding onto the ISs set in >> PCFieldSplitSetDefaults() or directly via PCFieldSplitSetIS() until they >> can be used in PCSetUp_FieldSplit(). I don't see how this can be avoided >> here or in the future, unless we do something to fundamentally change the >> set up process. >> >>> >>> >>>> The current interface assumes that the A00 solver and the Schur inner >>>> solver are to be set up identically >>>> >>> >>> If they are being set up identically, they should literally be the same >>> object. This is often the biggest setup cost in the whole problem (e.g. >>> AMG). >>> >> I agree, but that's available only in petsc-dev, not in petsc-3.3. The >> duplicate setup has been occurring all along, now it is actually consistent >> with the DM being forwarded to the inner solver. >> >>> >>> >>>> (something we relaxed in petsc-dev). In order to use fieldsplit on >>>> these solvers the DM for the corresponding split must be forwarded to both >>>> of these A00 solvers. It was being set only on the "outer" A00 solver. >>>> Partly this is an artifact of our "split" setup process: some of it occurs >>>> in PCFieldSplitSetDefaults(), some later in PCSetUp_FieldSplit(). Some >>>> objects obtained in PCFieldSplitSetDefaults() need to be cached until >>>> PCSetUp_FieldSplit(), and the splits' DMs are among those. I now put in >>>> proper reference counting for them here: >>>> http://petsc.cs.iit.edu/petsc/releases/petsc-3.3/rev/188af9799779 >>>> >>>> >>>>> Maybe we can reach some agreement on the proper way to do things. >>>>> >>>> That's fine with me. The reason I wanted to fix this particular >>>> problem now is that some dependent packages (e.g., Moose) only rely on >>>> release versions of petsc and would not be able to use this functionality >>>> properly for quite some time. >>>> >>> >>> Why do packages do this? Because petsc-dev is sometimes unstable. >>> >>> Now what happens when code that is pushed to the release changes >>> behavior and uses uninitialized memory? The release becomes unstable. >>> >>> Even worse, our nightly testing is targeted at petsc-dev because the >>> expectation is that only trivial and well-tested bug-fix patches are pushed >>> to release. If we are changing that model by introducing significant >>> changes, we MUST have nightly tests for the release, we have to actually >>> look at the results, and I would be strongly in favor of switching from >>> 3.3p3 numbering to 3.3.1. >>> >>> In all cases, these subminor or patch releases MUST be binary and >>> source-level backward compatible. >>> >>> >>>> Let's fix that "down the line". Setting a DM should never force it to >>>>> be used or cause an error due to unsupported operation in a case where not >>>>> having a DM is also acceptable. >>>>> >>>> Currently the inner and outer A00 solvers are essentially identified >>>> (duplicated), so they should be set up identically, including the DM. >>>> Especially when that DM defines a recursive split. This is in part >>>> because there is no way to configure those two differently programmatically >>>> or from the command line. So if the outer A00 is using >>>> -fieldsplit_0_pc_type_fieldsplit, the inner A00 will as well. >>>> However, the DM on the inner A00 will be rather different (or absent) >>>> and produce splits incompatible with the rest of the options (e.g., a >>>> single default split, while -fieldsplit_0_pc_fieldsplit_type schur). >>>> >>>> Incidentally, this raises this question down the road: in petsc-dev the >>>> inner and outer A00 can be configure separately using different prefixes, >>>> but how should the inner A00 DM be configured? >>>> >>> >>> The KSPs should only be different if the solver is different. Having >>> them separate, but using the same DM is one reason I was not wild about >>> having physics in the DM, but I don't see a good way to plumb in the extra >>> information. In any case, we need to come up with a solution before pushing >>> code. >>> >>> >>>> Okay, I'll back out that part of the second patch, since A11's >>>>>> nullspace is assumed to be meant for S. I'm not sure what's incorrect >>>>>> about the comment, though: if a vector is in the A11's kernel, but not in >>>>>> S's, I call it a "false positive". This terminology may be wanting, but >>>>>> what's incorrect about it? >>>>>> >>>>> >>>>> "force an inconsistent rhs" >>>>> >>>> The KSP solve will fail only if the search space X is contracted to the >>>> point where the rhs b is not in the range AX, hence, >>>> inconsistent. >>>> >>> >>> Okay, I just would have said that it changes the operator. Also, the >>> Krylov methods are not necessarily correct if the matrix does not have the >>> stated null space (since it's expected that the matrix has the null space >>> and only the preconditioner needs to be filtered). >>> >>> >>>> I backed out this hunk, however. >>>> >>>>> >>>>> S may well be nonsingular. >>>>> >>>>> >>>>>> >>>>>> >>>>>>> I think that's confusing and we need a specific API for it, but if >>>>>>> people are using it that way, we shouldn't change it in 3.3. >>>>>>> >>>>>>> I'd prefer to backout the first patch, split it into separate >>>>>>> pieces, and review each before pushing. I think it's a potentially big >>>>>>> behavior change for 3.3. >>>>>>> >>>>>> Which pieces of the first patch do you think are too big for 3.3? >>>>>> The splits' and Schur KSPs have to be set up (maybe not all in every >>>>>> situation) in order for recursive splitting to work. Should we declare >>>>>> that capability unavailable for 3.3? I can eliminate the unneeded >>>>>> KSPSetUp() calls. >>>>>> >>>>> >>>>> 1. I hate those hacky dm reference-non-references. >>>>> >>>>> 2. I don't want unused KSPs to be set up. (We should eventually fix >>>>> the model so they don't exist...) >>>>> >>>>> 3. Two of the three IncrementTabLevels that you introduced are not >>>>> necessary because the KSP's tab level was incremented before getting the >>>>> PC. >>>>> >>>> Where? >>>> >>> >>> ierr = >>> KSPCreate(((PetscObject)pc)->comm,&jac->kspschur);CHKERRQ(ierr); >>> ierr = >>> PetscLogObjectParent((PetscObject)pc,(PetscObject)jac->kspschur);CHKERRQ(ierr); >>> ierr = >>> PetscObjectIncrementTabLevel((PetscObject)jac->kspschur,(PetscObject)pc,1);CHKERRQ(ierr); >>> + { >>> + PC pcschur; >>> + ierr = KSPGetPC(jac->kspschur, &pcschur); >>> CHKERRQ(ierr); >>> + ierr = >>> PetscObjectIncrementTabLevel((PetscObject)pcschur,(PetscObject)pc,1);CHKERRQ(ierr); >>> + } >>> >>> >>> ierr = >>> KSPCreate(((PetscObject)pc)->comm,&ilink->ksp);CHKERRQ(ierr); >>> ierr = >>> PetscObjectIncrementTabLevel((PetscObject)ilink->ksp,(PetscObject)pc,1);CHKERRQ(ierr); >>> + { >>> + PC ilinkpc; >>> + ierr = KSPGetPC(ilink->ksp, &ilinkpc); CHKERRQ(ierr); >>> + ierr = >>> PetscObjectIncrementTabLevel((PetscObject)ilinkpc,(PetscObject)pc,1);CHKERRQ(ierr); >>> + } >>> >>> >>> This is the pattern used everywhere else in PETSc so that sub-pcs always >>> have the correct tab level. >>> >> >> > -------------- next part -------------- An HTML attachment was scrubbed... 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