[WIP] Multigrid with 3D implicit line agglomeration - #2863
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remove multigrid turbulence Co-authored-by: Nijso <nijso@hotmail.com>
Co-authored-by: Nijso <nijso@hotmail.com>
Co-authored-by: Nijso <nijso@hotmail.com>
Co-authored-by: Nijso <nijso@hotmail.com>
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## Proposed Changes This is a split from #2863 to clean up the different implementations. This PR does not really improve convergence, it merely implements some configuration options and makes it work robustly. An improvement comes from the CFL ramping: every level of the startup phase in FMG gets its own scaled CFL, then for this level CFL increases from the max CFL of the previous level to the new CFL of this level over MG_STARTUP_ITER iterations. This does mean some CFL jumps when you converge early. Also, when you exit the startup phase and enter the final v-cycle phase, you immediately jump to CFL_NUMBER, no ramping here. The real future improvement is probably stepping away from the piecewise constant interpolation. At the moment there is no improvement because the coarser levels do not result in a better starting point for the final v-cycle. Implementation details: MG_STARTUP_ITER= 100 %Full multigrid iterations per level for the warmup phase. MG_CFL_SCALING= 0.5, 0.5, 0.5 %Full multigrid now has CFL scaling for the coarser levels during warmup phase MG_STARTUP_CONVERGENCE= -2 %Full multigrid now exits the current level during the warmup phase when convergence dropped. MG_STARTUP_STAGNATION_ITER= 0.99 %Full multigrid now exits the current level during the warmup phase when the level residual stalls. MG_STARTUP_STAGNATION_ITER= 5 % 5 consecutive iteration of stagnation before exiting. ## Related Work #2863 ## PR Checklist *Put an X by all that apply. You can fill this out after submitting the PR. If you have any questions, don't hesitate to ask! We want to help. These are a guide for you to know what the reviewers will be looking for in your contribution.* - [x] I am submitting my contribution to the develop branch. - [x] My contribution generates no new compiler warnings (try with --warnlevel=3 when using meson). - [x] My contribution is commented and consistent with SU2 style (https://su2code.github.io/docs_v7/Style-Guide/). - [x] I used the pre-commit hook to prevent dirty commits and used `pre-commit run --all` to format old commits. - [x] I have added a test case that demonstrates my contribution, if necessary. - [ ] I have updated appropriate documentation (Tutorials, Docs Page, config_template.cpp), if necessary. --------- Co-authored-by: Claude Opus 5 <noreply@anthropic.com> Co-authored-by: Pedro Gomes <38071223+pcarruscag@users.noreply.github.com>
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Proposed Changes
[EDIT] moving the Full Multi-Grid stuff to a separate PR
fix full multigrid
MG_STARTUP_ITER= 50 as config option.
fix implicit line agglomeration
MG_IMPLICIT_LINES= YES
MG_IMPLICIT_LINES_MAX_LENGTH= 1000
MG_IMPLICIT_LINES_ISOTROPIC= YES
For isotropic=yes, every pair of 2x2 nodes is agglomerated, for isotropic=no, we only agglomerate in the direction normal to the implicit line, so the y+ values are preserved.
The implicit line agglomeration works for 2D and 3D, but has been tested more intensively on 2D cases.
Related Work
PR Checklist
Put an X by all that apply. You can fill this out after submitting the PR. If you have any questions, don't hesitate to ask! We want to help. These are a guide for you to know what the reviewers will be looking for in your contribution.
pre-commit run --allto format old commits.