Ling, ILU(level) is used for saving storage space with more computations. Normally, we use level=1 or 2. It does not make sense to use level 15. If you have sufficient space, LU would be the best. Hong
________________________________ From: petsc-users <petsc-users-boun...@mcs.anl.gov> on behalf of Zou, Ling via petsc-users <petsc-users@mcs.anl.gov> Sent: Wednesday, March 27, 2024 4:24 PM To: petsc-users@mcs.anl.gov <petsc-users@mcs.anl.gov> Subject: [petsc-users] Does ILU(15) still make sense or should just use LU? Hi, I’d like to avoid using LU, but in some cases to use ILU and still converge, I have to go to ILU(15), i.e., `-pc_factor_levels 15`. Does it still make sense, or should I give it up and switch to LU? For this particular case, ~2k DoF, and both ILU(15) and LU perform similarly in terms of wall time. -Ling
