BiCGStab and CG implementations: possible improvements #3587
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…s implemented in MLCGSolverT class.
eebasso
commented
Oct 6, 2023
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| MF sorig(ba, dm, ncomp, nghost, MFInfo(), factory); | ||
| MF p (ba, dm, ncomp, nghost, MFInfo(), factory); | ||
| MF r (ba, dm, ncomp, nghost, MFInfo(), factory); | ||
| MF s (ba, dm, ncomp, nghost, MFInfo(), factory); |
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The variable s can be eliminated by using residual r
eebasso
commented
Oct 6, 2023
| @@ -225,7 +215,14 @@ MLCGSolverT<MF>::solve_bicgstab (MF& sol, const MF& rhs, RT eps_rel, RT eps_abs) | |||
| { | |||
| ret = 4; break; | |||
| } | |||
| rho_1 = rho; | |||
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No need to save old rho as we only need rhTv to compute beta
eebasso
changed the title
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@eebasso A number of regression tests have failed. Some of them were just roundoff errors, but some produced NaNs. https://ccse.lbl.gov/pub/GpuRegressionTesting/AMReX/2023-11-01-003/index.html If it makes sense, baybe you could split this into a few small PRs. |
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I think splitting up into multiple PRs is quite reasonable. Shall I update this PR with a smaller change or close it and make a new PR ? |
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It might be cleaner to start new PRs. |
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Summary
Corrects some possible minor inefficiencies in the implementation of biconjugate gradient stabilized (BiCGStab) and conjugate gradient (CG) methods defined in MLCGSolverT class. The changes have not been tested yet. This should lead to no change in the outcomes, but hopefully will be faster by reducing memory usage and copy operations.
Additional background
See the attached pdf for a more in-depth explanation and comparison of current vs proposed
implementations. BiCGStab and CG algorithm summary.pdf
Checklist
The proposed changes: