Mark,
This will be tricky. It will take a bit of working figuring out how to pass
the Aggs properly to ASM.
> On Jun 23, 2016, at 7:16 AM, Mark Adams <[email protected]> wrote:
>
> I'm not sure how to create an empty subdomain in ASM. I get this error in
> KSPSetup. I think this is empty subdomains. The old code, that worked once,
> was giving me the errors that I sent before. Now I do this:
>
> if (!sz) {
> IS is;
> ierr = ISCreateGeneral(PETSC_COMM_SELF, 0, NULL, PETSC_COPY_VALUES,
> &is);CHKERRQ(ierr);
> ierr = PCASMSetLocalSubdomains(subpc, 1, &is, NULL);CHKERRQ(ierr);
> ierr = ISDestroy(&is);CHKERRQ(ierr);
> } else {
>
> I will keep digging.
>
> 14:09 mark/gamg-agg-asm *= ~/Codes/petsc/src/ksp/ksp/examples/tutorials$ make
> PETSC_ARCH=arch-macosx-gnu-O runex56
> [2]PETSC ERROR: #1 VecScatterCreate() line 1492 in
> /Users/markadams/Codes/petsc/src/vec/vec/utils/vscat.c
> [2]PETSC ERROR: #2 PCSetUp_ASM() line 279 in
> /Users/markadams/Codes/petsc/src/ksp/pc/impls/asm/asm.c
> [2]PETSC ERROR: #3 PCSetUp() line 968 in
> /Users/markadams/Codes/petsc/src/ksp/pc/interface/precon.c
> [2]PETSC ERROR: #4 KSPSetUp() line 390 in
> /Users/markadams/Codes/petsc/src/ksp/ksp/interface/itfunc.c
> [2]PETSC ERROR: #5 PCSetUp_MG() line 783 in
> /Users/markadams/Codes/petsc/src/ksp/pc/impls/mg/mg.c
> [2]PETSC ERROR: #6 PCSetUp_GAMG() line 675 in
> /Users/markadams/Codes/petsc/src/ksp/pc/impls/gamg/gamg.c
> [2]PETSC ERROR: #7 PCSetUp() line 968 in
> /Users/markadams/Codes/petsc/src/ksp/pc/interface/precon.c
> [2]PETSC ERROR: #8 KSPSetUp() line 390 in
> /Users/markadams/Codes/petsc/src/ksp/ksp/interface/itfunc.c
> [2]PETSC ERROR: #9 main() line 279 in
> /Users/markadams/Codes/petsc/src/ksp/ksp/examples/tutorials/ex56.c
>
>
> On Thu, Jun 23, 2016 at 7:08 AM, Mark Adams <[email protected]> wrote:
> [adding Garth]
>
> On Thu, Jun 23, 2016 at 12:52 AM, Barry Smith <[email protected]> wrote:
>
> Mark,
>
> I think there is a misunderstanding here. With GASM an individual block
> problem is __solved__ (via a parallel KSP) in parallel by several processes,
> with ASM each block is "owned" by and solved on a single process.
>
> Ah, OK, so this is for multiple processors in a block. Yes, we are looking at
> small, smother, blocks.
>
>
> With both the "block" can come from any unknowns on any processes. You can
> have, for example a block that comes from a region snaking across several
> processes if you like (or it makes sense due to coupling in the matrix).
>
> By default if you use ASM it will create one non-overlapping block defined
> by all unknowns owned by a single process and then extend it by "one level"
> (defined by the nonzero structure of the matrix) to get overlapping.
>
> The default in ASM is one level of overlap? That is new. (OK, I have not
> looked at ASM in like over 10 years)
>
> If you use multiple blocks per process it defines the non-overlapping blocks
> within a single process's unknowns
>
> I assume this still chops the matrix and does not call a partitioner.
>
> and extends each of them to have overlap (again by the non-zero structure of
> the matrix). The default is simple because the user only need indicate the
> number of blocks per process, the drawback is of course that it does depend
> on the process layout, number of processes etc and does not take into account
> particular "coupling information" that the user may know about with their
> problem.
>
> If the user wishes to defined the blocks themselves that is also possible
> with PCASMSetSubLocalSubdomains(). Each process provides 1 or more index sets
> for the subdomains it will solve on. Note that the index sets can contain any
> unknowns in the entire problem so the blocks do not have to "line up" with
> the parallel decomposition at all.
>
> Oh, OK, this is what I want. (I thought this worked).
>
> Of course determining and providing good such subdomains may not always be
> clear.
>
> In smoothed aggregation there is an argument that the aggregates are good,
> but the scale is fixed obviously. On a regular grid smoothed aggregation
> wants 3^D sized aggregates, which is obviously wonderful for AMS. And for
> anisotropy you want your ASM blocks to be on strongly connected components,
> which is what smoothed aggregation wants (not that I do this very well).
>
>
> I see in GAMG you have PCGAMGSetUseASMAggs
>
> But the code calls PCGASMSetSubdomains and the command line is
> -pc_gamg_use_agg_gasm, so this is all messed up. (more below)
>
> which sadly does not have an explanation in the users manual and sadly does
> not have a matching options data base name -pc_gamg_use_agg_gasm following
> the rule of drop the word set, all lower case, and put _ between words the
> option should be -pc_gamg_use_asm_aggs.
>
> BUT, THIS IS THE WAY IT WAS! It looks like someone hijacked this code and
> made it gasm. I never did this.
>
> Barry: you did this apparently in 2013.
>
>
> In addition to this one you could also have one that uses the aggs but use
> the PCASM to manage the solves instead of GASM, it would likely be less buggy
> and more efficient.
>
> yes
>
>
> Please tell me exactly what example you tried to run with what options and
> I will debug it.
>
> We got an error message:
>
> ** Max-trans not allowed because matrix is distributed
>
> Garth: is this from your code perhaps? I don't see it in PETSc.
>
> Note that ALL functionality that is included in PETSc should have tests that
> test that functionality then we will find out immediately when it is broken
> instead of two years later when it is much harder to debug. If this
> -pc_gamg_use_agg_gasm had had a test we won't be in this mess now. (Jed's
> damn code reviews sure don't pick up this stuff).
>
> First we need to change gasm to asm.
>
> We could add this argument pc_gamg_use_agg_asm to ksp/ex56 (runex56 or make
> a new test). The SNES version (also ex56) is my current test that I like to
> refer to as recommended parameters for elasticity. So I'd like to keep that
> clean, but we can add junk to ksp/ex56.
>
> I've done this in a branch mark/gamg-agg-asm. I get an error (appended). It
> looks like the second coarsest grid, which has 36 dof on one processor has an
> index 36 in the block on every processor. Strange. I can take a look at it
> later.
>
> Mark
>
> > [3]PETSC ERROR: [4]PETSC ERROR: --------------------- Error Message
> > --------------------------------------------------------------
> > [4]PETSC ERROR: Petsc has generated inconsistent data
> > [4]PETSC ERROR: ith 0 block entry 36 not owned by any process, upper bound
> > 36
> > [4]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for
> > trouble shooting.
> > [4]PETSC ERROR: Petsc Development GIT revision: v3.7.2-630-g96e0c40 GIT
> > Date: 2016-06-22 10:03:02 -0500
> > [4]PETSC ERROR: ./ex56 on a arch-macosx-gnu-g named MarksMac-3.local by
> > markadams Thu Jun 23 06:53:27 2016
> > [4]PETSC ERROR: Configure options COPTFLAGS="-g -O0" CXXOPTFLAGS="-g -O0"
> > FOPTFLAGS="-g -O0" --download-hypre=1 --download-parmetis=1
> > --download-metis=1 --download-ml=1 --download-p4est=1 --download-exodus=1
> > --download-triangle=1 --with-hdf5-dir=/Users/markadams/Codes/hdf5
> > --with-x=0 --with-debugging=1 PETSC_ARCH=arch-macosx-gnu-g --download-chaco
> > [4]PETSC ERROR: #1 VecScatterCreate_PtoS() line 2348 in
> > /Users/markadams/Codes/petsc/src/vec/vec/utils/vpscat.c
> > [4]PETSC ERROR: #2 VecScatterCreate() line 1552 in
> > /Users/markadams/Codes/petsc/src/vec/vec/utils/vscat.c
> > [4]PETSC ERROR: Petsc has generated inconsistent data
> > [3]PETSC ERROR: ith 0 block entry 36 not owned by any process, upper bound
> > 36
> > [3]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for
> > trouble shooting.
> > [3]PETSC ERROR: Petsc Development GIT revision: v3.7.2-630-g96e0c40 GIT
> > Date: 2016-06-22 10:03:02 -0500
> > [3]PETSC ERROR: ./ex56 on a arch-macosx-gnu-g named MarksMac-3.local by
> > markadams Thu Jun 23 06:53:27 2016
> > [3]PETSC ERROR: Configure options COPTFLAGS="-g -O0" CXXOPTFLAGS="-g -O0"
> > FOPTFLAGS="-g -O0" --download-hypre=1 --download-parmetis=1
> > --download-metis=1 --download-ml=1 --download-p4est=1 --download-exodus=1
> > --download-triangle=1 --with-hdf5-dir=/Users/markadams/Codes/hdf5
> > --with-x=0 --with-debugging=1 PETSC_ARCH=arch-macosx-gnu-g --download-chaco
> > [3]PETSC ERROR: #1 VecScatterCreate_PtoS() line 2348 in
> > /Users/markadams/Codes/petsc/src/vec/vec/utils/vpscat.c
> > [3]PETSC ERROR: #2 VecScatterCreate() line 1552 in
> > /Users/markadams/Codes/petsc/src/vec/vec/utils/vscat.c
> > [3]PETSC ERROR: #3 PCSetUp_ASM() line 279 in
> > /Users/markadams/Codes/petsc/src/ksp/pc/impls/asm/asm.c
>
>
>
>
>
>
>
> Barry
>
>
>
>
>
>
> > On Jun 22, 2016, at 5:20 PM, Mark Adams <[email protected]> wrote:
> >
> >
> >
> > On Wed, Jun 22, 2016 at 8:06 PM, Barry Smith <[email protected]> wrote:
> >
> > I suggest focusing on asm.
> >
> > OK, I will switch gasm to asm, this does not work anyway.
> >
> > Having blocks that span multiple processes seems like over kill for a
> > smoother ?
> >
> > No, because it is a pain to have the math convolved with the parallel
> > decompositions strategy (ie, I can't tell an application how to partition
> > their problem). If an aggregate spans processor boundaries, which is fine
> > and needed, and let's say we have a pretty uniform problem, then if the
> > block gets split up, H is small in part of the domain and convergence could
> > suffer along processor boundaries. And having the math change as the
> > parallel decomposition changes is annoying.
> >
> > (Major league overkill) in fact doesn't one want multiple blocks per
> > process, ie. pretty small blocks.
> >
> > No, it is just doing what would be done in serial. If the cost of moving
> > the data across the processor is a problem then that is a tradeoff to
> > consider.
> >
> > And I think you are misunderstanding me. There are lots of blocks per
> > process (the aggregates are say 3^D in size). And many of the
> > aggregates/blocks along the processor boundary will be split between
> > processors, resulting is mall blocks and weak ASM PC on processor
> > boundaries.
> >
> > I can understand ASM not being general and not letting blocks span
> > processor boundaries, but I don't think the extra matrix communication
> > costs are a big deal (done just once) and the vector communication costs
> > are not bad, it probably does not include (too many) new processors to
> > communicate with.
> >
> >
> > Barry
> >
> > > On Jun 22, 2016, at 7:51 AM, Mark Adams <[email protected]> wrote:
> > >
> > > I'm trying to get block smoothers to work for gamg. We (Garth) tried
> > > this and got this error:
> > >
> > >
> > > - Another option is use '-pc_gamg_use_agg_gasm true' and use
> > > '-mg_levels_pc_type gasm'.
> > >
> > >
> > > Running in parallel, I get
> > >
> > > ** Max-trans not allowed because matrix is distributed
> > > ----
> > >
> > > First, what is the difference between asm and gasm?
> > >
> > > Second, I need to fix this to get block smoothers. This used to work.
> > > Did we lose the capability to have blocks that span processor subdomains?
> > >
> > > gamg only aggregates across processor subdomains within one layer, so
> > > maybe I could use one layer of overlap in some way?
> > >
> > > Thanks,
> > > Mark
> > >
> >
> >
>
>
>
