[petsc-users] Reuse hypre interpolations between successive KSPOnly solves associated with TSStep ?

[Sajid Ali]

Hi PETSc-developers,

For a linear TS, when solving with -ts_type cn -ksp_type fgmres -pc_type
gamg, the flag -pc_gamg_reuse_interpolation can be used to re-use the GAMG
interpolation calculated when solving the first time step. Increasing the
number of time steps only increases the time spent in application of the
precondition and the setup time is constant.

Is there an equivalent way to do this with Hypre’s BoomerAMG ? I’m using
euclid as the smoother but adding the -pc_hypre_euclid_reuse flag only
seems to make it reuse the euclid ILU smoothing within a particular TS time
step, i.e. increasing the number of time steps linearly increases the time
spent in setting up the preconditioner.

Another approach I tried was to use hypre within the PCHMG preconditioner
(which I hoped would allow me to use BoomerAMG to computer interpolations
while also reusing the interpolations via the -pc_hmg_reuse_interpolation
flag.) However, I’m unable to pass the parameter to BoomerAMG when Hypre is
set as the inner PC for the HMG preconditioner. I didn’t see any options
for doing so when I searched the -help output and neither does setting
options via -hmg_inner_pc_hypre_boomeramg_option value work. What am I
missing here ?

For reference, I’m adding the exact solver options used (and the associated
log files) for each of the above cases if it helps. (GAMG was used on the
system of equations arising out of the complex PDE but since I was unable
to get good convergence rates with GAMG for the real equivalent of the
same, I switched to Hypre which performed better. Hence I’m looking for a
way to set the reuse interpolation feature for this as well.)

Thank You,
Sajid Ali | PhD Candidate
Applied Physics
Northwestern University
s-sajid-ali.github.io
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