[petsc-users] FGMRES and BCGS

[Marco Cisternino]

Good Morning,
I usually solve a non-symmetric discretization of the Poisson equation using GAMG+FGMRES.
In the last days I tried to use BCGS in place of FGMRES, still using GAMG as preconditioner.
No problem in finding the solution but I'm experiencing something I didn't expect.
The test case is a 25 millions cells domain with Dirichlet and Neumann boundary conditions.
Both the solvers are able to solve the problem with an increasing number of MPI processes, but:

  *   FGMRES is about 25% faster than BCGS for all the processes number
  *   Both solvers have the same scalability from 48 to 384 processes
  *   Both solvers almost use the same amount of memory (FGMRES use a restart=30)
Am I wrong expecting less memory consumption and more performance from BCGS with respect to FGMRES?
Thank you in advance for any help.

Best regards,
Marco Cisternino


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