Hi, Justin, I don't know ASM well enough. I just browsed its code. It seems it has a lot of matrix partitioning and indexing operations, which definitely are not done on GPUs currently. But you could still try that, as petsc will copy data from the device to the host as needed to perform host-only operations. You can profile with -log_vew -log_view_gpu_time so that we can see how expensive these operations are.
Barry should know more about ASM. --Junchao Zhang On Tue, Apr 15, 2025 at 10:43 AM Angus, Justin Ray <ang...@llnl.gov> wrote: > Hi Junchao, > > > > Thanks for the reply. > > > > Does ASM work the same on GPU systems as it does on CPU systems? > > > > *From: *Junchao Zhang <junchao.zh...@gmail.com> > *Date: *Monday, April 14, 2025 at 7:35 PM > *To: *Angus, Justin Ray <ang...@llnl.gov> > *Cc: *petsc-dev@mcs.anl.gov <petsc-dev@mcs.anl.gov>, Ghosh, Debojyoti < > gho...@llnl.gov> > *Subject: *Re: [petsc-dev] Additive Schwarz Method + ILU on GPU platforms > > Petsc supports ILU0/ICC0 numeric factorization (without reordering) and > then triangular solve on GPUs. It is done by calling vendor libraries (ex. > cusparse). > > We have options -pc_factor_mat_factor_on_host <bool> > -pc_factor_mat_solve_on_host <bool> to force doing the factorization and > MatSolve on the host for device matrix types. > > > > You can try to see if it works for your case. > > > > --Junchao Zhang > > > > > > On Mon, Apr 14, 2025 at 4:39 PM Angus, Justin Ray via petsc-dev < > petsc-dev@mcs.anl.gov> wrote: > > Hello, > > > > A project I work on uses GMRES via PETSc. In particular, we have had good > successes using the Additive Schwarz Method + ILU preconditioner setup > using a CPU-based code. I found online where it is stated that “Parts of > most preconditioners run directly on the GPU” ( > https://urldefense.us/v3/__https://petsc.org/release/faq/__;!!G_uCfscf7eWS!Z8bOHrIJpUl9O8A9Z3SKLCa5vOhktluqMMJsYNsnLi92XNwl0gLCRaWy6TPoNDZns8N8wpd1UmnSEVkpvySgQkVMSsIT$ > > <https://urldefense.us/v3/__https:/petsc.org/release/faq/__;!!G_uCfscf7eWS!bw6qeKcY7MKSvlEgcogdKR7fpjZSOFvka6zfDprUZ_sJHdE-YZmRD6UTqWQW3_uGVBII4P-AG0zaGTLbI67_fQ$>). > Is ASM + ILU also available for GPU platforms? > > > > -Justin > >
