Implement subcell limiting for non-conservative systems by amrueda · Pull Request #1670 · trixi-framework/Trixi.jl

amrueda · 2023-10-10T15:55:56Z

This PR extends the subcell limiting strategies implemented in #1476 to non-conservative systems.

To do the subcell limiting, the DGSEM is formulated as a flux-differencing formula. For non-conservative systems, this formulation requires expressing non-conservative terms as the product of both local and symmetric components. I have included an example using the GLM-MHD equations, where the Powell and GLM non-conservative terms have been recast in the format of "local * symmetric."

…ative systems -> A working version of this implementation is added for the GLM-MHD system -> The flux-differencing formula requires non-conservative terms of the form (local * symmetric)... I modified equations/ideal_glm_mhd_2d.jl and solvers/dgsem_tree/dg_2d.jl to make it work -> In this first implementation, we only use the Powell term and deactivate the GLM term

…2d.jl back to its original state

…ve terms

…he modified Powell source term. This was needed due to incompatibility on non-conforming meshes.

github-actions · 2023-10-10T16:00:00Z

codecov · 2023-10-10T17:39:12Z

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (0f49e5b) 90.84% compared to head (e836b7f) 82.73%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1670      +/-   ##
==========================================
- Coverage   90.84%   82.73%   -8.11%     
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  Files         430      431       +1     
  Lines       34437    34672     +235     
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Files	Coverage Δ
...tree_2d_dgsem/elixir_mhd_shockcapturing_subcell.jl	`100.00% <100.00%> (ø)`
src/Trixi.jl	`43.48% <ø> (ø)`
...llbacks_stage/subcell_limiter_idp_correction_2d.jl	`94.12% <100.00%> (ø)`
src/equations/equations.jl	`98.11% <100.00%> (+0.07%)`	⬆️
src/equations/ideal_glm_mhd_2d.jl	`98.80% <100.00%> (+14.51%)`	⬆️
src/solvers/dgsem_tree/containers_2d.jl	`57.14% <100.00%> (-39.49%)`	⬇️
src/solvers/dgsem_tree/dg_2d_subcell_limiters.jl	`99.56% <100.00%> (+0.71%)`	⬆️
src/solvers/dgsem_tree/subcell_limiters_2d.jl	`94.74% <100.00%> (ø)`
src/time_integration/methods_SSP.jl	`83.70% <100.00%> (+0.36%)`	⬆️

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amrueda · 2023-10-11T09:02:43Z

I ran a convergence test (5 different meshes and polydeg = 3) with a modified version of examples/tree_2d_dgsem/elixir_mhd_alfven_wave.jl, where I activated the positivity limiter. The l2 and linf errors are equal to the ones produced by VolumeIntegralShockCapturingHG and VolumeIntegralFluxDifferencing to machine precision accuracy. Here are the convergence tables:

l2
rho                 rho_v1              rho_v2              rho_v3              rho_e               B1                  B2                  B3                  psi
error     EOC       error     EOC       error     EOC       error     EOC       error     EOC       error     EOC       error     EOC       error     EOC       error     EOC
5.51e-03  -         4.77e-04  -         4.77e-04  -         9.35e-04  -         2.84e-04  -         3.73e-04  -         3.73e-04  -         9.33e-04  -         3.80e-04  -
9.09e-04  2.60      5.81e-05  3.04      5.81e-05  3.04      8.11e-05  3.53      2.34e-05  3.60      2.09e-05  4.16      2.09e-05  4.16      4.08e-05  4.51      9.42e-06  5.33
1.11e-04  3.03      5.94e-06  3.29      5.94e-06  3.29      8.54e-06  3.25      1.32e-06  4.15      1.47e-06  3.83      1.47e-06  3.83      2.16e-06  4.24      4.65e-07  4.34
9.46e-06  3.56      4.82e-07  3.62      4.82e-07  3.62      7.11e-07  3.59      8.35e-08  3.98      1.19e-07  3.63      1.19e-07  3.63      1.67e-07  3.69      2.81e-08  4.05
3.17e-07  4.90      2.10e-08  4.52      2.10e-08  4.52      2.85e-08  4.64      4.19e-09  4.32      1.28e-08  3.21      1.28e-08  3.21      1.80e-08  3.22      1.74e-09  4.01

mean      3.52      mean      3.62      mean      3.62      mean      3.75      mean      4.01      mean      3.71      mean      3.71      mean      3.92      mean      4.43
----------------------------------------------------------------------------------------------------
linf
rho                 rho_v1              rho_v2              rho_v3              rho_e               B1                  B2                  B3                  psi
error     EOC       error     EOC       error     EOC       error     EOC       error     EOC       error     EOC       error     EOC       error     EOC       error     EOC
1.33e-02  -         1.97e-03  -         1.97e-03  -         2.68e-03  -         1.09e-03  -         1.99e-03  -         1.99e-03  -         3.71e-03  -         1.14e-03  -
1.86e-03  2.83      1.80e-04  3.45      1.80e-04  3.45      2.45e-04  3.45      8.61e-05  3.66      1.28e-04  3.95      1.28e-04  3.95      2.31e-04  4.00      3.86e-05  4.88
2.68e-04  2.80      1.73e-05  3.38      1.73e-05  3.38      2.61e-05  3.23      5.46e-06  3.98      9.23e-06  3.80      9.23e-06  3.80      1.40e-05  4.05      2.37e-06  4.02
2.35e-05  3.51      1.39e-06  3.64      1.39e-06  3.64      2.71e-06  3.27      3.56e-07  3.94      6.15e-07  3.91      6.15e-07  3.91      8.90e-07  3.97      1.47e-07  4.01
9.69e-07  4.60      9.39e-08  3.88      9.39e-08  3.88      9.04e-08  4.90      2.40e-08  3.89      4.71e-08  3.71      4.71e-08  3.71      6.77e-08  3.72      9.15e-09  4.00

mean      3.44      mean      3.59      mean      3.59      mean      3.71      mean      3.87      mean      3.84      mean      3.84      mean      3.94      mean      4.23
----------------------------------------------------------------------------------------------------

amrueda · 2023-10-11T15:26:40Z

When running the convergence test documented above, the following performance summary was obtained with the novel subcell limiting for non-conservative systems and one thread:

  ────────────────────────────────────────────────────────────────────────────────────────
                Trixi.jl                        Time                    Allocations
                                       ───────────────────────   ────────────────────────
           Tot / % measured:                 125s /  97.4%           3.03GiB /  99.9%

 Section                       ncalls     time    %tot     avg     alloc    %tot      avg
 ────────────────────────────────────────────────────────────────────────────────────────
 rhs!                           4.87k     103s   84.6%  21.2ms   11.5KiB    0.0%    2.43B
   volume integral              4.87k    84.0s   68.9%  17.3ms   2.20KiB    0.0%    0.46B
     calcflux_fhat!             19.9M    45.9s   37.6%  2.30μs     0.00B    0.0%    0.00B
     calcflux_fv!               19.9M    22.0s   18.1%  1.10μs     0.00B    0.0%    0.00B
     calcflux_antidiffusive!    19.9M    8.47s    6.9%   425ns     0.00B    0.0%    0.00B
     ~volume integral~          4.87k    7.67s    6.3%  1.58ms   2.20KiB    0.0%    0.46B
   interface flux               4.87k    11.7s    9.6%  2.40ms     0.00B    0.0%    0.00B
   prolong2interfaces           4.87k    3.37s    2.8%   693μs     0.00B    0.0%    0.00B
   surface integral             4.87k    2.04s    1.7%   419μs     0.00B    0.0%    0.00B
   reset ∂u/∂t                  4.87k    1.33s    1.1%   273μs     0.00B    0.0%    0.00B
   Jacobian                     4.87k    593ms    0.5%   122μs     0.00B    0.0%    0.00B
   ~rhs!~                       4.87k   24.6ms    0.0%  5.05μs   9.33KiB    0.0%    1.96B
   prolong2boundaries           4.87k   1.97ms    0.0%   406ns     0.00B    0.0%    0.00B
   prolong2mortars              4.87k   1.83ms    0.0%   376ns     0.00B    0.0%    0.00B
   mortar flux                  4.87k   1.44ms    0.0%   296ns     0.00B    0.0%    0.00B
   boundary flux                4.87k    266μs    0.0%  54.6ns     0.00B    0.0%    0.00B
   source terms                 4.87k    220μs    0.0%  45.2ns     0.00B    0.0%    0.00B
 a posteriori limiter           4.87k    12.1s   10.0%  2.49ms   1.47KiB    0.0%    0.31B
   blending factors             4.87k    7.01s    5.8%  1.44ms      752B    0.0%    0.15B
     positivity                 4.87k    6.41s    5.3%  1.32ms     0.00B    0.0%    0.00B
     ~blending factors~         4.87k    602ms    0.5%   124μs      752B    0.0%    0.15B
   ~a posteriori limiter~       4.87k    5.12s    4.2%  1.05ms      752B    0.0%    0.15B
 I/O                              165    3.64s    3.0%  22.1ms   2.17GiB   71.6%  13.4MiB
   save solution                  164    3.63s    3.0%  22.1ms   2.17GiB   71.5%  13.5MiB
   get element variables          164   7.10ms    0.0%  43.3μs   1.44MiB    0.0%  8.98KiB
   ~I/O~                          165   2.00ms    0.0%  12.1μs    379KiB    0.0%  2.30KiB
   save mesh                      164   59.1μs    0.0%   360ns     0.00B    0.0%    0.00B
 calculate dt                   1.62k    2.15s    1.8%  1.32ms     0.00B    0.0%    0.00B
 analyze solution                  18    888ms    0.7%  49.3ms    880MiB   28.4%  48.9MiB
 ────────────────────────────────────────────────────────────────────────────────────────

The summary obtained with VolumeIntegralShockCapturingHG and one thread is:

 ────────────────────────────────────────────────────────────────────────────────────
              Trixi.jl                      Time                    Allocations      
                                   ───────────────────────   ────────────────────────
         Tot / % measured:              49.9s /  94.0%           3.03GiB /  99.9%    

 Section                   ncalls     time    %tot     avg     alloc    %tot      avg
 ────────────────────────────────────────────────────────────────────────────────────
 rhs!                       4.87k    41.2s   87.8%  8.47ms   11.5KiB    0.0%    2.43B
   volume integral          4.87k    25.2s   53.6%  5.17ms   2.20KiB    0.0%    0.46B
     pure DG                4.87k    21.8s   46.5%  4.48ms     0.00B    0.0%    0.00B
     blending factors       4.87k    3.23s    6.9%   663μs     0.00B    0.0%    0.00B
     ~volume integral~      4.87k    103ms    0.2%  21.1μs   2.20KiB    0.0%    0.46B
     blended DG-FV          4.87k   1.04ms    0.0%   213ns     0.00B    0.0%    0.00B
   interface flux           4.87k    11.3s   24.0%  2.32ms     0.00B    0.0%    0.00B
   prolong2interfaces       4.87k    1.77s    3.8%   364μs     0.00B    0.0%    0.00B
   surface integral         4.87k    1.70s    3.6%   350μs     0.00B    0.0%    0.00B
   reset ∂u/∂t              4.87k    754ms    1.6%   155μs     0.00B    0.0%    0.00B
   Jacobian                 4.87k    556ms    1.2%   114μs     0.00B    0.0%    0.00B
   ~rhs!~                   4.87k   17.1ms    0.0%  3.51μs   9.33KiB    0.0%    1.96B
   prolong2mortars          4.87k   2.41ms    0.0%   496ns     0.00B    0.0%    0.00B
   prolong2boundaries       4.87k   2.28ms    0.0%   468ns     0.00B    0.0%    0.00B
   source terms             4.87k    716μs    0.0%   147ns     0.00B    0.0%    0.00B
   mortar flux              4.87k    687μs    0.0%   141ns     0.00B    0.0%    0.00B
   boundary flux            4.87k    371μs    0.0%  76.3ns     0.00B    0.0%    0.00B
 I/O                          165    2.96s    6.3%  17.9ms   2.17GiB   71.6%  13.4MiB
   save solution              164    2.84s    6.0%  17.3ms   2.17GiB   71.5%  13.5MiB
   get element variables      164    115ms    0.2%   704μs   1.41MiB    0.0%  8.80KiB
   ~I/O~                      165   1.89ms    0.0%  11.5μs    379KiB    0.0%  2.30KiB
   save mesh                  164   77.8μs    0.0%   474ns     0.00B    0.0%    0.00B
 calculate dt               1.62k    2.08s    4.4%  1.28ms     0.00B    0.0%    0.00B
 analyze solution              18    676ms    1.4%  37.5ms    881MiB   28.4%  48.9MiB
 ────────────────────────────────────────────────────────────────────────────────────

It is clear that the volume integral with subcell limiting is significantly more expensive than VolumeIntegralShockCapturingHG. Some extra cost was expected due to the fact that the new volume integral computes two non-conservative terms (Powell and GLM separately) instead of one. However, this seems like an extreme slow down. I tried to improve the performance, but so far this is the best I achieved...

Co-authored-by: Hendrik Ranocha <ranocha@users.noreply.github.com>

amrueda · 2023-10-12T09:13:19Z

Thanks for your comments, @ranocha! I already applied your suggestions and replied to your questions.

Do you have any clue of what might be making my code slow? (see performance post)

It seems that my problem is in the function calcflux_fhat!, which is taking a total of 45.9s to compute the DG volume integral with non-conservative terms for the test above. This is more than twice the time needed by flux_differencing_kernel!, which takes 21.8s to compute the DG volume integral with non-conservative terms.

As I wrote above,

Some extra cost was expected due to the fact that the new volume integral computes two non-conservative terms (Powell and GLM separately) instead of one. However, this seems like an extreme slow down.

Do you see any performance issues in calcflux_fhat!? or do you have any idea about how I can speed up that function?

ranocha · 2023-10-13T17:44:25Z

Do you have any clue of what might be making my code slow? (see performance post)

It seems that my problem is in the function calcflux_fhat!, which is taking a total of 45.9s to compute the DG volume integral with non-conservative terms for the test above. This is more than twice the time needed by flux_differencing_kernel!, which takes 21.8s to compute the DG volume integral with non-conservative terms.

As I wrote above,

Some extra cost was expected due to the fact that the new volume integral computes two non-conservative terms (Powell and GLM separately) instead of one. However, this seems like an extreme slow down.

Do you see any performance issues in calcflux_fhat!? or do you have any idea about how I can speed up that function?

Did you try starting Julia with the flag --check-bounds=no? It appears to make a significant difference for me in this case.

amrueda · 2023-10-16T07:35:46Z

Did you try starting Julia with the flag --check-bounds=no? It appears to make a significant difference for me in this case.

Yes, the results I reported were obtained with --check-bounds=no.

…d multiple dispatch

Co-authored-by: Michael Schlottke-Lakemper <michael@sloede.com>

…vative equations Co-authored-by: Benjamin Bolm <74359358+bennibolm@users.noreply.github.com>

Co-authored-by: Hendrik Ranocha <ranocha@users.noreply.github.com>

ranocha

Thanks

…ut a method Co-authored-by: Michael Schlottke-Lakemper <michael@sloede.com>

Co-authored-by: Michael Schlottke-Lakemper <michael@sloede.com>

sloede

LGTM!

amrueda added 8 commits October 5, 2023 17:47

Modified non-conservative fluxes to revert src/solvers/dgsem_tree/dg_…

67e379f

…2d.jl back to its original state

Subcell limiting: Added the possibility to use multiple nonconservati…

12c6c1d

…ve terms

Added some comments and improved formatting

7017914

Added expected results for MHD subcell limiting test

5119d97

Restored old Powell source term and created a new function name for t…

ad6177e

…he modified Powell source term. This was needed due to incompatibility on non-conforming meshes.

Fixed bug

9158093

Fixed bug

3dcccc4

amrueda added 4 commits October 11, 2023 11:30

Moved new multiple-dispatch structs for to equations.jl

adb930e

Improved allocations

b0e3aad

Avoid double computation of local part of non-conservative flux

e0a3fdf

Improved subcell volume integral in y direction and formatting

86884e8

ranocha reviewed Oct 11, 2023

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amrueda commented Oct 12, 2023

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amrueda and others added 4 commits October 12, 2023 10:22

Apply suggestions from code review

0d61cfd

Co-authored-by: Hendrik Ranocha <ranocha@users.noreply.github.com>

Added timers and corrected docstrings

b0caf8e

Improved formatting

6dae80a

Reduced testing time

0c2e24e

amrueda mentioned this pull request Oct 12, 2023

WIP: Implement subcell limiting for non-conservative systems amrueda/Trixi.jl#4

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bennibolm reviewed Oct 12, 2023

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amrueda added 2 commits October 16, 2023 09:42

Renamed variables for consistency

20abe7b

Merge branch 'main' into subcell_limiting_noncons

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amrueda added 2 commits October 24, 2023 15:24

Added explanatory comments about different non-conservative fluxes an…

120f9ba

…d multiple dispatch

Changed variable name noncons_term to nonconservative_term

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