feat(autoware_ground_segmentation): grid data structure revision for efficiency improve

[technolojin]

Description

Change data structure of grid for calculation efficiency improvement.

1. (Performance) Grid and grid cells are defined
2. (Performance) The grid geometry is modeled to Concentric Zone Model (CZM) based polar grid
3. (Refactor) The grid process is separated from node.cpp
4. (Performance) The segmentation process is ran cell-wise (while current process is point-wise).
5. (Performance) Replace arc tangent (atan2) to a pseudo arc tangent function for better performance (with accuracy drop, which can be acceptable)

How the efficiency is improved

1. By replacing existing data structure, sorting is not needed.
2. Segmentation condition (connected, disconnected, break) is determined grid cell-wise, not point-wise.
3. Concentric Zone Model (CZM) based polar grid allows to make various grid cell density. The grid is configured to have lower number of the grids close to the ego vehicle. Less grid cells means lower cell-related calculation.
4. The arc tangent is used for grid allocation on each points. The grid cell allocation do not require high accuracy, therefore, it can be replaced by approximation.

Drawbacks

1. Introducing CZM polar grid requires cell geometry calculation. If the number of cell grids is large, the calculation can take longer time.
2. Finding non-empty grid cell take calculation cost. Increase by the number of cell grids.
3. If the grid cells contains few points, performance improvement will be limited.

Drawback mitigation

set the parameter grid_size_m to 0.5
PR autowarefoundation/autoware_launch#1223

Related links

Parent Issue:

• Link

How was this PR tested?

Performance test (check degradation)

TIER IV INTERNAL

Processing time

Before

Computation time difference by grid size is negligible.

• Before: grid_size_m: 0.1

🌲 Total Processing Time Tree 🌲
100.00% faster_filter: total 3118.96 [ms], avg. 12.89 [ms], run count: 242
    ├── 74.77% convertPointcloudGridScan: total 2332.12 [ms], avg. 9.64 [ms], run count: 242
    │   ├── 52.53% azimuth_angle_grouping: total 1638.31 [ms], avg. 6.77 [ms], run count: 242
    │   ├── 22.12% sort: total 690.03 [ms], avg. 2.85 [ms], run count: 242
    │   └── 0.12% rest: 3.79 [ms]
    ├── 22.85% classifyPointCloudGridScan: total 712.62 [ms], avg. 2.94 [ms], run count: 242
    ├── 1.53% extractObjectPoints: total 47.75 [ms], avg. 0.20 [ms], run count: 242
    └── 0.85% rest: 26.46 [ms]

• Before: grid_size_m: 0.2

🌲 Total Processing Time Tree 🌲
100.00% faster_filter: total 3129.68 [ms], avg. 12.88 [ms], run count: 243
    ├── 76.50% convertPointcloudGridScan: total 2394.23 [ms], avg. 9.85 [ms], run count: 243
    │   ├── 54.11% azimuth_angle_grouping: total 1693.44 [ms], avg. 6.97 [ms], run count: 243
    │   ├── 22.28% sort: total 697.30 [ms], avg. 2.87 [ms], run count: 243
    │   └── 0.11% rest: 3.49 [ms]
    ├── 21.30% classifyPointCloudGridScan: total 666.66 [ms], avg. 2.74 [ms], run count: 243
    ├── 1.34% extractObjectPoints: total 41.92 [ms], avg. 0.17 [ms], run count: 243
    └── 0.86% rest: 26.87 [ms]

• Before: grid_size_m: 0.5

🌲 Total Processing Time Tree 🌲
100.00% faster_filter: total 3012.68 [ms], avg. 12.66 [ms], run count: 238
    ├── 78.02% convertPointcloudGridScan: total 2350.36 [ms], avg. 9.88 [ms], run count: 238
    │   ├── 55.51% azimuth_angle_grouping: total 1672.34 [ms], avg. 7.03 [ms], run count: 238
    │   ├── 22.39% sort: total 674.44 [ms], avg. 2.83 [ms], run count: 238
    │   └── 0.12% rest: 3.58 [ms]
    ├── 19.86% classifyPointCloudGridScan: total 598.35 [ms], avg. 2.51 [ms], run count: 238
    ├── 1.28% extractObjectPoints: total 38.42 [ms], avg. 0.16 [ms], run count: 238
    └── 0.85% rest: 25.56 [ms]

• Before: grid_size_m: 1.0

🌲 Total Processing Time Tree 🌲
100.00% faster_filter: total 3021.20 [ms], avg. 12.54 [ms], run count: 241
    ├── 78.97% convertPointcloudGridScan: total 2385.86 [ms], avg. 9.90 [ms], run count: 241
    │   ├── 55.63% azimuth_angle_grouping: total 1680.76 [ms], avg. 6.97 [ms], run count: 241
    │   ├── 23.22% sort: total 701.58 [ms], avg. 2.91 [ms], run count: 241
    │   └── 0.12% rest: 3.52 [ms]
    ├── 18.84% classifyPointCloudGridScan: total 569.28 [ms], avg. 2.36 [ms], run count: 241
    ├── 1.32% extractObjectPoints: total 39.87 [ms], avg. 0.17 [ms], run count: 241
    └── 0.87% rest: 26.19 [ms]

After

The larger grid size, the lower computation time.

• After: grid_size_m: 0.1

🌲 Total Processing Time Tree 🌲
100.00% faster_filter: total 4829.41 [ms], avg. 19.96 [ms], run count: 242
    ├── 98.48% process: total 4755.83 [ms], avg. 19.65 [ms], run count: 242
    │   ├── 8.14% resetCells: total 392.91 [ms], avg. 1.62 [ms], run count: 242
    │   ├── 21.71% convert: total 1048.67 [ms], avg. 4.33 [ms], run count: 242
    │   ├── 10.50% preprocess: total 507.22 [ms], avg. 2.10 [ms], run count: 242
    │   │   ├── 10.49% setGridConnections: total 506.39 [ms], avg. 2.09 [ms], run count: 242
    │   │   └── 0.02% rest: 0.83 [ms]
    │   ├── 4.58% initializeGround: total 221.22 [ms], avg. 0.91 [ms], run count: 242
    │   ├── 53.39% classify: total 2578.31 [ms], avg. 10.65 [ms], run count: 242
    │   └── 0.16% rest: 7.50 [ms]
    ├── 1.17% extractObjectPoints: total 56.59 [ms], avg. 0.23 [ms], run count: 242
    └── 0.35% rest: 16.99 [ms]

• After: grid_size_m: 0.2

🌲 Total Processing Time Tree 🌲
100.00% faster_filter: total 3486.55 [ms], avg. 14.35 [ms], run count: 243
    ├── 97.94% process: total 3414.80 [ms], avg. 14.05 [ms], run count: 243
    │   ├── 6.08% resetCells: total 212.07 [ms], avg. 0.87 [ms], run count: 243
    │   ├── 24.60% convert: total 857.85 [ms], avg. 3.53 [ms], run count: 243
    │   ├── 6.70% preprocess: total 233.55 [ms], avg. 0.96 [ms], run count: 243
    │   │   ├── 6.68% setGridConnections: total 232.85 [ms], avg. 0.96 [ms], run count: 243
    │   │   └── 0.02% rest: 0.70 [ms]
    │   ├── 3.73% initializeGround: total 130.04 [ms], avg. 0.54 [ms], run count: 243
    │   ├── 56.65% classify: total 1975.29 [ms], avg. 8.13 [ms], run count: 243
    │   └── 0.17% rest: 6.00 [ms]
    ├── 1.57% extractObjectPoints: total 54.74 [ms], avg. 0.23 [ms], run count: 243
    └── 0.49% rest: 17.01 [ms]

• After: grid_size_m: 0.5

🌲 Total Processing Time Tree 🌲
100.00% faster_filter: total 2503.10 [ms], avg. 10.26 [ms], run count: 244
    ├── 97.29% process: total 2435.27 [ms], avg. 9.98 [ms], run count: 244
    │   ├── 3.21% resetCells: total 80.33 [ms], avg. 0.33 [ms], run count: 244
    │   ├── 29.74% convert: total 744.51 [ms], avg. 3.05 [ms], run count: 244
    │   ├── 3.09% preprocess: total 77.26 [ms], avg. 0.32 [ms], run count: 244
    │   │   ├── 3.05% setGridConnections: total 76.42 [ms], avg. 0.31 [ms], run count: 244
    │   │   └── 0.03% rest: 0.84 [ms]
    │   ├── 1.97% initializeGround: total 49.26 [ms], avg. 0.20 [ms], run count: 244
    │   ├── 59.07% classify: total 1478.57 [ms], avg. 6.06 [ms], run count: 244
    │   └── 0.21% rest: 5.35 [ms]
    ├── 1.95% extractObjectPoints: total 48.80 [ms], avg. 0.20 [ms], run count: 244
    └── 0.76% rest: 19.03 [ms]

• After: grid_size_m: 1.0

🌲 Total Processing Time Tree 🌲
100.00% faster_filter: total 1989.49 [ms], avg. 8.22 [ms], run count: 242
    ├── 96.41% process: total 1918.08 [ms], avg. 7.93 [ms], run count: 242
    │   ├── 2.04% resetCells: total 40.52 [ms], avg. 0.17 [ms], run count: 242
    │   ├── 34.13% convert: total 679.11 [ms], avg. 2.81 [ms], run count: 242
    │   ├── 1.59% preprocess: total 31.61 [ms], avg. 0.13 [ms], run count: 242
    │   │   ├── 1.56% setGridConnections: total 31.09 [ms], avg. 0.13 [ms], run count: 242
    │   │   └── 0.03% rest: 0.52 [ms]
    │   ├── 1.71% initializeGround: total 34.12 [ms], avg. 0.14 [ms], run count: 242
    │   ├── 56.69% classify: total 1127.92 [ms], avg. 4.66 [ms], run count: 242
    │   └── 0.24% rest: 4.80 [ms]
    ├── 2.55% extractObjectPoints: total 50.80 [ms], avg. 0.21 [ms], run count: 242
    └── 1.04% rest: 20.61 [ms]

Notes for reviewers

None.

Interface changes

None.

Effects on system behavior

None.

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[codecov]

Codecov Report

Attention: Patch coverage is 85.46169% with 74 lines in your changes missing coverage. Please review.

Project coverage is 14.60%. Comparing base (1ab29fd) to head (980e054).
Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
...tion/src/scan_ground_filter/grid_ground_filter.cpp	88.74%	14 Missing and 12 partials ⚠️
...round_segmentation/src/scan_ground_filter/grid.hpp	88.42%	7 Missing and 15 partials ⚠️
...tion/src/scan_ground_filter/grid_ground_filter.hpp	68.08%	11 Missing and 4 partials ⚠️
...round_segmentation/src/scan_ground_filter/node.cpp	72.00%	5 Missing and 2 partials ⚠️
...round_segmentation/src/scan_ground_filter/data.hpp	75.00%	1 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #9297       +/-   ##
===========================================
- Coverage   29.19%   14.60%   -14.59%     
===========================================
  Files        1333       84     -1249     
  Lines      102795     5978    -96817     
  Branches    39870     1407    -38463     
===========================================
- Hits        30008      873    -29135     
+ Misses      69926     4984    -64942     
+ Partials     2861      121     -2740     

Flag	Coverage Δ
differential	14.60% <85.46%> (?)
total	?

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