On Sun, Oct 30, 2022 at 3:52 PM Barry Smith <bsm...@petsc.dev> wrote:
> > In general you should expect similar but not identical conference > behavior. > > I suggest running with all the monitoring you can. > -ksp_monitor_true_residual > -fieldsplit_0_monitor_true_residual -fieldsplit_1_monitor_true_residual and > compare the various convergence between the CPU and GPU. Also run with > -ksp_view and check that the various solver options are the same (they > should be). > Is the GPU using float or double? Matt > Barry > > > On Oct 30, 2022, at 11:02 AM, Carl-Johan Thore via petsc-users < > petsc-users@mcs.anl.gov> wrote: > > Hi, > > I'm solving a topology optimization problem with Stokes flow discretized > by a stabilized Q1-Q0 finite element method > and using BiCGStab with the fieldsplit preconditioner to solve the linear > systems. The implementation > is based on DMStag, runs on Ubuntu via WSL2, and works fine with > PETSc-3.18.1 on multiple CPU cores and the following > options for the preconditioner: > > -fieldsplit_0_ksp_type preonly \ > -fieldsplit_0_pc_type gamg \ > -fieldsplit_0_pc_gamg_reuse_interpolation 0 \ > -fieldsplit_1_ksp_type preonly \ > -fieldsplit_1_pc_type jacobi > > However, when I enable GPU computations by adding two options - > > ... > -dm_vec_type cuda \ > -dm_mat_type aijcusparse \ > -fieldsplit_0_ksp_type preonly \ > -fieldsplit_0_pc_type gamg \ > -fieldsplit_0_pc_gamg_reuse_interpolation 0 \ > -fieldsplit_1_ksp_type preonly \ > -fieldsplit_1_pc_type jacobi > > - KSP still works fine the first couple of topology optimization > iterations but then > stops with "Linear solve did not converge due to DIVERGED_DTOL ..". > > My question is whether I should expect the GPU versions of the linear > solvers and pre-conditioners > to function exactly as their CPU counterparts (I got this impression from > the documentation), > in which case I've probably made some mistake in my own code, or whether > there are other/additional > settings or modifications I should use to run on the GPU (an NVIDIA Quadro > T2000)? > > Kind regards, > > Carl-Johan > > > -- 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/>