> Message: 5 > Date: Fri, 24 Jun 2016 08:59:57 -0500 > From: Barry Smith <[email protected]> > To: Mark Adams <[email protected]> > Cc: For users of the development version of PETSc > <[email protected]> > Subject: Re: [petsc-dev] asm / gasm > Message-ID: <[email protected]> > Content-Type: text/plain; charset="us-ascii" > > > > On Jun 24, 2016, at 1:35 AM, Mark Adams <[email protected]> wrote: > > > > > > > > On Thu, Jun 23, 2016 at 11:46 PM, Barry Smith <[email protected]> > wrote: > > > > Mark, > > > > It is not as simple as this to convert to ASM. It will take a little > bit of work to use ASM here instead of GASM. > > > > > > Just to be clear: ASM used to work. Did the semantics of ASM change? >
Hi Mark, Assume that you said GASM used to work, and now is not working any more. GASM was originally written by Dmitry. The basic idea is to allow mulit-rank blocks, that is, a mulit-rank subdomain problem could be solved using a small number of processor cores in parallel. This is different from ASM. I was involved into the development of GASM last summer. There are some changes: (1) Added a function to increase overlap of the multi-rank subdomains. The function is called by GASM in default. (2) Added a hierarchical partitioning to optimize data exchange. Ensure that small subdomains in a multi-rank subdomain are geometrically connected. GASM does not use this functionality in default. Any way, if you have an example (like Barry asked) showing the broken GASM, I will debug into it (of course, if Barry does not mind). Fande Kong, > > Show me a commit where ASM worked! Do you mean that the GASM worked? > The code has GASM calls in it, not ASM so how could ASM have previously > worked? It is possible that something changed in GASM that broke GAMG's > usage of GASM. Once you tell me how to reproduce the problem with GASM I > can try to track down the problem. > > > > > But before that please please tell me the command line argument and > example you use where the GASM crashes so I can get that fixed. Then I will > look at using ASM instead after I have the current GASM code running again. > > > > In branch mark/gamg-agg-asm in ksp ex56, 'make runex56': > > I don't care about this! This is where you have tried to change from > GASM to ASM which I told you is non-trivial. Give me the example and > command line where the GASM version in master (or maint) doesn't work where > the error message includes ** Max-trans not allowed because matrix is > distributed > > We are not communicating very well, you jumped from stating GASM > crashed to monkeying with ASM and now refuse to tell me how to reproduce > the GASM crash. We have to start by fixing the current code to work with > GASM (if it ever worked) and then move on to using ASM (which is just an > optimization of the GASM usage.) > > > Barry > > > > > > 14:12 nid00495 ~/petsc/src/ksp/ksp/examples/tutorials$ make runex56 > > [0]PETSC ERROR: --------------------- Error Message > -------------------------------------------------------------- > > [0]PETSC ERROR: Petsc has generated inconsistent data > > [0]PETSC ERROR: MPI_Allreduce() called in different locations (code > lines) on different processors > > [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html > for trouble shooting. > > [0]PETSC ERROR: Petsc Development GIT revision: v3.7.2-633-g4f88208 GIT > Date: 2016-06-23 18:53:31 +0200 > > [0]PETSC ERROR: > /global/u2/m/madams/petsc/src/ksp/ksp/examples/tutorials/./ex56 on a > arch-xc30-dbg64-intel named nid00495 by madams Thu Jun 23 14:12:57 2016 > > [0]PETSC ERROR: Configure options --COPTFLAGS="-no-ipo -g -O0" > --CXXOPTFLAGS="-no-ipo -g -O0" --FOPTFLAGS="-fast -no-ipo -g -O0" > --download-parmetis --download-metis --with-ssl=0 --with-cc=cc > --with-clib-autodetect=0 --with-cxx=CC --with-cxxlib-autodetect=0 > --with-debugging=1 --with-fc=0 --with-shared-libraries=0 --with-x=0 > --with-mpiexec=srun LIBS=-lstdc++ --with-64-bit-indices > PETSC_ARCH=arch-xc30-dbg64-intel > > [0]PETSC ERROR: #1 MatGetSubMatrices_MPIAIJ() li > > > > > > > > > > > > > > > > > > > > > > Barry > > > > > > > On Jun 23, 2016, at 4:19 PM, Mark Adams <[email protected]> wrote: > > > > > > The question boils down to, for empty processors do we: > > > > > > 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); > > > > > > or > > > > > > PCASMSetLocalSubdomains(subpc, 0, NULL, NULL); > > > > > > The later gives and error that one domain is need and the later gives > an error (appended). > > > > > > I've checked in the code for this second error in ksp (make runex56) > > > > > > Thanks, > > > > > > [0]PETSC ERROR: --------------------- Error Message > -------------------------------------------------------------- > > > [0]PETSC ERROR: Petsc has generated inconsistent data > > > [0]PETSC ERROR: MPI_Allreduce() called in different locations (code > lines) on different processors > > > [0]PETSC ERROR: See > http://www.mcs.anl.gov/petsc/documentation/faq.html for trouble shooting. > > > [0]PETSC ERROR: Petsc Development GIT revision: v3.7.2-633-g4f88208 > GIT Date: 2016-06-23 18:53:31 +0200 > > > [0]PETSC ERROR: > /global/u2/m/madams/petsc/src/ksp/ksp/examples/tutorials/./ex56 on a > arch-xc30-dbg64-intel named nid00495 by madams Thu Jun 23 14:12:57 2016 > > > [0]PETSC ERROR: Configure options --COPTFLAGS="-no-ipo -g -O0" > --CXXOPTFLAGS="-no-ipo -g -O0" --FOPTFLAGS="-fast -no-ipo -g -O0" > --download-parmetis --download-metis --with-ssl=0 --with-cc=cc > --with-clib-autodetect=0 --with-cxx=CC --with-cxxlib-autodetect=0 > --with-debugging=1 --with-fc=0 --with-shared-libraries=0 --with-x=0 > --with-mpiexec=srun LIBS=-lstdc++ --with-64-bit-indices > PETSC_ARCH=arch-xc30-dbg64-intel > > > [0]PETSC ERROR: #1 MatGetSubMatrices_MPIAIJ() line 1147 in > /global/u2/m/madams/petsc/src/mat/impls/aij/mpi/mpiov.c > > > [0]PETSC ERROR: #2 MatGetSubMatrices_MPIAIJ() line 1147 in > /global/u2/m/madams/petsc/src/mat/impls/aij/mpi/mpiov.c > > > [1]PETSC ERROR: --------------------- Error Message > -------------------------------------------------------------- > > > > > > On Thu, Jun 23, 2016 at 8:05 PM, Barry Smith <[email protected]> > wrote: > > > > > > Where is the command line that generates the error? > > > > > > > > > > On Jun 23, 2016, at 12:08 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 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > ------------------------------ > > _______________________________________________ > petsc-dev mailing list > [email protected] > https://lists.mcs.anl.gov/mailman/listinfo/petsc-dev > > > End of petsc-dev Digest, Vol 90, Issue 30 > ***************************************** >
