On Thu, Dec 21, 2023 at 6:46 AM Sreeram R Venkat <srven...@utexas.edu> wrote:
> Ok, I think the error I'm getting has something to do with how the > multiple solves are being done in succession. I'll try to see if there's > anything I'm doing wrong there. > > One question about the -pc_type lu -ksp_type preonly method: do you know > which parts of the solve (factorization/triangular solves) are done on host > and which are done on device? > For SEQDENSE, I believe both the factorization and solve is on device. It is hard to see, but I believe the dispatch code is here: https://gitlab.com/petsc/petsc/-/blob/main/src/mat/impls/dense/seq/cupm/matseqdensecupm.hpp?ref_type=heads#L368 Thanks, Matt > Thanks, > Sreeram > > On Sat, Dec 16, 2023 at 10:56 PM Pierre Jolivet <pie...@joliv.et> wrote: > >> Unfortunately, I am not able to reproduce such a failure with your input >> matrix. >> I’ve used ex79 that I linked previously and the system is properly solved. >> $ ./ex79 -pc_type hypre -ksp_type hpddm -ksp_hpddm_type cg >> -ksp_converged_reason -ksp_view_mat ascii::ascii_info -ksp_view_rhs >> ascii::ascii_info >> Linear solve converged due to CONVERGED_RTOL iterations 6 >> Mat Object: 1 MPI process >> type: seqaijcusparse >> rows=289, cols=289 >> total: nonzeros=2401, allocated nonzeros=2401 >> total number of mallocs used during MatSetValues calls=0 >> not using I-node routines >> Mat Object: 1 MPI process >> type: seqdensecuda >> rows=289, cols=10 >> total: nonzeros=2890, allocated nonzeros=2890 >> total number of mallocs used during MatSetValues calls=0 >> >> You mentioned in a subsequent email that you are interested in systems >> with at most 1E6 unknowns, and up to 1E4 right-hand sides. >> I’m not sure you can expect significant gains from using GPU for such >> systems. >> Probably, the fastest approach would indeed be -pc_type lu -ksp_type >> preonly -ksp_matsolve_batch_size 100 or something, depending on the memory >> available on your host. >> >> Thanks, >> Pierre >> >> On 15 Dec 2023, at 9:52 PM, Sreeram R Venkat <srven...@utexas.edu> wrote: >> >> Here are the ksp_view files. I set the options >> -ksp_error_if_not_converged to try to get the vectors that caused the >> error. I noticed that some of the KSPMatSolves converge while others don't. >> In the code, the solves are called as: >> >> input vector v --> insert data of v into a dense mat --> KSPMatSolve() >> --> MatMatMult() --> KSPMatSolve() --> insert data of dense mat into output >> vector w -- output w >> >> The operator used in the KSP is a Laplacian-like operator, and the >> MatMatMult is with a Mass Matrix. The whole thing is supposed to be a solve >> with a biharmonic-like operator. I can also run it with only the first >> KSPMatSolve (i.e. just a Laplacian-like operator). In that case, the KSP >> reportedly converges after 0 iterations (see the next line), but this >> causes problems in other parts of the code later on. >> >> I saw that sometimes the first KSPMatSolve "converges" after 0 iterations >> due to CONVERGED_RTOL. Then, the second KSPMatSolve produces a NaN/Inf. I >> tried setting ksp_min_it, but that didn't seem to do anything. >> >> I'll keep trying different options and also try to get the MWE made (this >> KSPMatSolve is pretty performance critical for us). >> >> Thanks for all your help, >> Sreeram >> >> On Fri, Dec 15, 2023 at 1:01 AM Pierre Jolivet <pie...@joliv.et> wrote: >> >>> >>> On 14 Dec 2023, at 11:45 PM, Sreeram R Venkat <srven...@utexas.edu> >>> wrote: >>> >>> Thanks, I will try to create a minimal reproducible example. This may >>> take me some time though, as I need to figure out how to extract only the >>> relevant parts (the full program this solve is used in is getting quite >>> complex). >>> >>> >>> You could just do -ksp_view_mat binary:Amat.bin -ksp_view_pmat >>> binary:Pmat.bin -ksp_view_rhs binary:rhs.bin and send me those three files >>> (I’m guessing your are using double-precision scalars with 32-bit PetscInt). >>> >>> I'll also try out some of the BoomerAMG options to see if that helps. >>> >>> >>> These should work (this is where all “PCMatApply()-ready” PC are being >>> tested): >>> https://petsc.org/release/src/ksp/ksp/tutorials/ex79.c.html#line215 >>> You can see it’s also testing PCHYPRE + KSPHPDDM on device (but not with >>> HIP). >>> I’m aware the performance should not be optimal (see your comment about >>> host/device copies), I’ve money to hire someone to work on this but: a) I >>> need to find the correct engineer/post-doc, b) I currently don’t have good >>> use cases (of course, I could generate a synthetic benchmark, for science). >>> So even if you send me the three Mat, a MWE would be appreciated if the >>> KSPMatSolve() is performance-critical for you (see point b) from above). >>> >>> Thanks, >>> Pierre >>> >>> Thanks, >>> Sreeram >>> >>> On Thu, Dec 14, 2023, 1:12 PM Pierre Jolivet <pie...@joliv.et> wrote: >>> >>>> >>>> >>>> On 14 Dec 2023, at 8:02 PM, Sreeram R Venkat <srven...@utexas.edu> >>>> wrote: >>>> >>>> Hello Pierre, >>>> >>>> Thank you for your reply. I tried out the HPDDM CG as you said, and it >>>> seems to be doing the batched solves, but the KSP is not converging due to >>>> a NaN or Inf being generated. I also noticed there are a lot of >>>> host-to-device and device-to-host copies of the matrices (the non-batched >>>> KSP solve did not have any memcopies). I have attached dump.0 again. Could >>>> you please take a look? >>>> >>>> >>>> Yes, but you’d need to send me something I can run with your set of >>>> options (if you are more confident doing this in private, you can remove >>>> the list from c/c). >>>> Not all BoomerAMG smoothers handle blocks of right-hand sides, and >>>> there is not much error checking, so instead of erroring out, this may be >>>> the reason why you are getting garbage. >>>> >>>> Thanks, >>>> Pierre >>>> >>>> Thanks, >>>> Sreeram >>>> >>>> On Thu, Dec 14, 2023 at 12:42 AM Pierre Jolivet <pie...@joliv.et> >>>> wrote: >>>> >>>>> Hello Sreeram, >>>>> KSPCG (PETSc implementation of CG) does not handle solves with >>>>> multiple columns at once. >>>>> There is only a single native PETSc KSP implementation which handles >>>>> solves with multiple columns at once: KSPPREONLY. >>>>> If you use --download-hpddm, you can use a CG (or GMRES, or more >>>>> advanced methods) implementation which handles solves with multiple >>>>> columns >>>>> at once (via -ksp_type hpddm -ksp_hpddm_type cg or KSPSetType(ksp, >>>>> KSPHPDDM); KSPHPDDMSetType(ksp, KSP_HPDDM_TYPE_CG);). >>>>> I’m the main author of HPDDM, there is preliminary support for device >>>>> matrices, but if it’s not working as intended/not faster than column by >>>>> column, I’d be happy to have a deeper look (maybe in private), because >>>>> most >>>>> (if not all) of my users interested in (pseudo-)block Krylov solvers >>>>> (i.e., >>>>> solvers that treat right-hand sides in a single go) are using plain host >>>>> matrices. >>>>> >>>>> Thanks, >>>>> Pierre >>>>> >>>>> PS: you could have a look at >>>>> https://www.sciencedirect.com/science/article/abs/pii/S0898122121000055 to >>>>> understand the philosophy behind block iterative methods in PETSc (and in >>>>> HPDDM), src/mat/tests/ex237.c, the benchmark I mentioned earlier, was >>>>> developed in the context of this paper to produce Figures 2-3. Note that >>>>> this paper is now slightly outdated, since then, PCHYPRE and PCMG (among >>>>> others) have been made “PCMatApply()-ready”. >>>>> >>>>> On 13 Dec 2023, at 11:05 PM, Sreeram R Venkat <srven...@utexas.edu> >>>>> wrote: >>>>> >>>>> Hello Pierre, >>>>> >>>>> I am trying out the KSPMatSolve with the BoomerAMG preconditioner. >>>>> However, I am noticing that it is still solving column by column (this is >>>>> stated explicitly in the info dump attached). I looked at the code for >>>>> KSPMatSolve_Private() and saw that as long as ksp->ops->matsolve is >>>>> true, it should do the batched solve, though I'm not sure where that gets >>>>> set. >>>>> >>>>> I am using the options -pc_type hypre -pc_hypre_type boomeramg when >>>>> running the code. >>>>> >>>>> Can you please help me with this? >>>>> >>>>> Thanks, >>>>> Sreeram >>>>> >>>>> >>>>> On Thu, Dec 7, 2023 at 4:04 PM Mark Adams <mfad...@lbl.gov> wrote: >>>>> >>>>>> N.B., AMGX interface is a bit experimental. >>>>>> Mark >>>>>> >>>>>> On Thu, Dec 7, 2023 at 4:11 PM Sreeram R Venkat <srven...@utexas.edu> >>>>>> wrote: >>>>>> >>>>>>> Oh, in that case I will try out BoomerAMG. Getting AMGX to build >>>>>>> correctly was also tricky so hopefully the HYPRE build will be easier. >>>>>>> >>>>>>> Thanks, >>>>>>> Sreeram >>>>>>> >>>>>>> On Thu, Dec 7, 2023, 3:03 PM Pierre Jolivet <pie...@joliv.et> wrote: >>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> On 7 Dec 2023, at 9:37 PM, Sreeram R Venkat <srven...@utexas.edu> >>>>>>>> wrote: >>>>>>>> >>>>>>>> Thank you Barry and Pierre; I will proceed with the first option. >>>>>>>> >>>>>>>> I want to use the AMGX preconditioner for the KSP. I will try it >>>>>>>> out and see how it performs. >>>>>>>> >>>>>>>> >>>>>>>> Just FYI, AMGX does not handle systems with multiple RHS, and thus >>>>>>>> has no PCMatApply() implementation. >>>>>>>> BoomerAMG does, and there is a PCMatApply_HYPRE_BoomerAMG() >>>>>>>> implementation. >>>>>>>> But let us know if you need assistance figuring things out. >>>>>>>> >>>>>>>> Thanks, >>>>>>>> Pierre >>>>>>>> >>>>>>>> Thanks, >>>>>>>> Sreeram >>>>>>>> >>>>>>>> On Thu, Dec 7, 2023 at 2:02 PM Pierre Jolivet <pie...@joliv.et> >>>>>>>> wrote: >>>>>>>> >>>>>>>>> To expand on Barry’s answer, we have observed repeatedly that >>>>>>>>> MatMatMult with MatAIJ performs better than MatMult with MatMAIJ, you >>>>>>>>> can >>>>>>>>> reproduce this on your own with >>>>>>>>> https://petsc.org/release/src/mat/tests/ex237.c.html. >>>>>>>>> Also, I’m guessing you are using some sort of preconditioner >>>>>>>>> within your KSP. >>>>>>>>> Not all are “KSPMatSolve-ready”, i.e., they may treat blocks of >>>>>>>>> right-hand sides column by column, which is very inefficient. >>>>>>>>> You could run your code with -info dump and send us dump.0 to see >>>>>>>>> what needs to be done on our end to make things more efficient, >>>>>>>>> should you >>>>>>>>> not be satisfied with the current performance of the code. >>>>>>>>> >>>>>>>>> Thanks, >>>>>>>>> Pierre >>>>>>>>> >>>>>>>>> On 7 Dec 2023, at 8:34 PM, Barry Smith <bsm...@petsc.dev> wrote: >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> On Dec 7, 2023, at 1:17 PM, Sreeram R Venkat <srven...@utexas.edu> >>>>>>>>> wrote: >>>>>>>>> >>>>>>>>> I have 2 sequential matrices M and R (both MATSEQAIJCUSPARSE of >>>>>>>>> size n x n) and a vector v of size n*m. v = [v_1 , v_2 ,... , v_m] >>>>>>>>> where >>>>>>>>> v_i has size n. The data for v can be stored either in column-major or >>>>>>>>> row-major order. Now, I want to do 2 types of operations: >>>>>>>>> >>>>>>>>> 1. Matvecs of the form M*v_i = w_i, for i = 1..m. >>>>>>>>> 2. KSPSolves of the form R*x_i = v_i, for i = 1..m. >>>>>>>>> >>>>>>>>> From what I have read on the documentation, I can think of 2 >>>>>>>>> approaches. >>>>>>>>> >>>>>>>>> 1. Get the pointer to the data in v (column-major) and use it to >>>>>>>>> create a dense matrix V. Then do a MatMatMult with M*V = W, and take >>>>>>>>> the >>>>>>>>> data pointer of W to create the vector w. For KSPSolves, use >>>>>>>>> KSPMatSolve >>>>>>>>> with R and V. >>>>>>>>> >>>>>>>>> 2. Create a MATMAIJ using M/R and use that for matvecs directly >>>>>>>>> with the vector v. I don't know if KSPSolve with the MATMAIJ will >>>>>>>>> know that >>>>>>>>> it is a multiple RHS system and act accordingly. >>>>>>>>> >>>>>>>>> Which would be the more efficient option? >>>>>>>>> >>>>>>>>> >>>>>>>>> Use 1. >>>>>>>>> >>>>>>>>> >>>>>>>>> As a side-note, I am also wondering if there is a way to use >>>>>>>>> row-major storage of the vector v. >>>>>>>>> >>>>>>>>> >>>>>>>>> No >>>>>>>>> >>>>>>>>> The reason is that this could allow for more coalesced memory >>>>>>>>> access when doing matvecs. >>>>>>>>> >>>>>>>>> >>>>>>>>> PETSc matrix-vector products use BLAS GMEV matrix-vector >>>>>>>>> products for the computation so in theory they should already be >>>>>>>>> well-optimized >>>>>>>>> >>>>>>>>> >>>>>>>>> Thanks, >>>>>>>>> Sreeram >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>> <dump.0> >>>>> >>>>> >>>>> <dump.0> >>>> >>>> >>>> >>> <Pmat.bin><Amat.bin><rhs.bin> >> >> >> -- 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/>