[petsc-dev] PETSc amg solver with gpu seems run slowly

[Qi Yang]

To whom it may concern,

I have tried petsc ex50(Possion) with cuda, ksp cg solver and
gamg precondition, however, it run for about 30s. I also tried NVIDIA AMGX
with the same solver and same grid (3000*3000), it only took 2s. I used
nsight system software to analyze those two cases, found petsc took much
time in the memory process (63% of total time, however, amgx only took
19%). Attached are screenshots of them.

The petsc command is : mpiexec -n 1 ./ex50  -da_grid_x 3000 -da_grid_y 3000
-ksp_type cg -pc_type gamg -pc_gamg_type agg -pc_gamg_agg_nsmooths 1
-vec_type cuda -mat_type aijcusparse -ksp_monitor -ksp_view -log-view

The log file is also attached.

Regards,
Qi

[image: 1.png]
[image: 2.png]
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