Barry, Mark and Matt, Thank you all for the suggestions. I will modify the code so we can pass runtime options.
Cho ________________________________ From: Barry Smith <bsm...@petsc.dev> Sent: Friday, June 30, 2023 7:01 AM To: Mark Adams <mfad...@lbl.gov> Cc: Matthew Knepley <knep...@gmail.com>; Ng, Cho-Kuen <c...@slac.stanford.edu>; petsc-users@mcs.anl.gov <petsc-users@mcs.anl.gov> Subject: Re: [petsc-users] Using PETSc GPU backend Note that options like -mat_type aijcusparse -vec_type cuda only work if the program is set up to allow runtime swapping of matrix and vector types. If you have a call to MatCreateMPIAIJ() or other specific types then then these options do nothing but because Mark had you use -options_left the program will tell you at the end that it did not use the option so you will know. On Jun 30, 2023, at 9:30 AM, Mark Adams <mfad...@lbl.gov> wrote: PetscCall(PetscInitialize(&argc, &argv, NULL, help)); gives us the args and you run: a.out -mat_type aijcusparse -vec_type cuda -log_view -options_left Mark On Fri, Jun 30, 2023 at 6:16 AM Matthew Knepley <knep...@gmail.com<mailto:knep...@gmail.com>> wrote: On Fri, Jun 30, 2023 at 1:13 AM Ng, Cho-Kuen via petsc-users <petsc-users@mcs.anl.gov<mailto:petsc-users@mcs.anl.gov>> wrote: Mark, The application code reads in parameters from an input file, where we can put the PETSc runtime options. Then we pass the options to PetscInitialize(...). Does that sounds right? PETSc will read command line argument automatically in PetscInitialize() unless you shut it off. Thanks, Matt Cho ________________________________ From: Ng, Cho-Kuen <c...@slac.stanford.edu<mailto:c...@slac.stanford.edu>> Sent: Thursday, June 29, 2023 8:32 PM To: Mark Adams <mfad...@lbl.gov<mailto:mfad...@lbl.gov>> Cc: petsc-users@mcs.anl.gov<mailto:petsc-users@mcs.anl.gov> <petsc-users@mcs.anl.gov<mailto:petsc-users@mcs.anl.gov>> Subject: Re: [petsc-users] Using PETSc GPU backend Mark, Thanks for the information. How do I put the runtime options for the executable, say, a.out, which does not have the provision to append arguments? Do I need to change the C++ main to read in the options? Cho ________________________________ From: Mark Adams <mfad...@lbl.gov<mailto:mfad...@lbl.gov>> Sent: Thursday, June 29, 2023 5:55 PM To: Ng, Cho-Kuen <c...@slac.stanford.edu<mailto:c...@slac.stanford.edu>> Cc: petsc-users@mcs.anl.gov<mailto:petsc-users@mcs.anl.gov> <petsc-users@mcs.anl.gov<mailto:petsc-users@mcs.anl.gov>> Subject: Re: [petsc-users] Using PETSc GPU backend Run with options: -mat_type aijcusparse -vec_type cuda -log_view -options_left The last column of the performance data (from -log_view) will be the percent flops on the GPU. Check that that is > 0. The end of the output will list the options that were used and options that were _not_ used (if any). Check that there are no options left. Mark On Thu, Jun 29, 2023 at 7:50 PM Ng, Cho-Kuen via petsc-users <petsc-users@mcs.anl.gov<mailto:petsc-users@mcs.anl.gov>> wrote: I installed PETSc on Perlmutter using "spack install petsc+cuda+zoltan" and used it by "spack load petsc/fwge6pf". Then I compiled the application code (purely CPU code) linking to the petsc package, hoping that I can get performance improvement using the petsc GPU backend. However, the timing was the same using the same number of MPI tasks with and without GPU accelerators. Have I missed something in the process, for example, setting up PETSc options at runtime to use the GPU backend? Thanks, Cho -- 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/>
