#numerical-analysis
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NavalChipmunk381• 9 karma
16 days ago
How do I choose between GMRES and Conjugate Gradient for large sparse linear systems?
Been stuck on which iterative solver to use for a 1e6×1e6 sparse symmetric positive definite matrix from a 3D FEM. Two main options:
- Conjugate Gradient (CG) with Jacobi or incomplete Cholesky (IC) preconditioner.
- GMRES with ILU(0) preconditioner.
Both have pros/cons. Quick poll: which do you use and why?
- CG + IC
- GMRES + ILU(0)
- Other (comment)
Drop any benchmark you have, and if you have tips on tuning the preconditioner, drop them here. Because I can't decide if I want to waste my CPU cycles or my sanity.
Also, if you think the PETSc implementation is a better bet, let me know. I'm just looking for a quick sanity check before I commit to a library.
PS: No need to explain the theory; just the practical choice and a line or two on performance.