5.0 KiB
Workshop performance, 2026-10-30
The flat-six workshop now runs within the real-time audio budget. The measured simulation cost fell from 104.44 to 8.79 microseconds per sample (11.9 times faster). At 44,100 Hz the available budget is 22.68 microseconds per sample.
Cause and changes
The workshop used a different assembly path from the native scenarios. It split fluid sections at every visual pipe knot, inserted 5 mm inlet stubs, required at least four fluid substeps per sample, and repeated mechanical/control work in each substep. Flat6 consequently had a 1.78 mm cell and averaged 12.35 substeps per sample. Its native scenario had a 34.20 mm minimum cell and about one substep.
- Mesh each pipe by total arclength and its diameter profile. Visual knots remain in the editor and renderer; exact frustum averages preserve gas volume.
- Advance shaft, ECU, cams, combustion, carburetors and pump displacement at the audio sample rate, matching native engine scheduling. Keep CFL stepping for fluid transport and pressure-operated check valves. Compile active part/gate lists and cache fixed restriction areas.
- Place the importer's metering assembly farther upstream within its existing inlet segment, allowing a sensible outlet stub. The inlet endpoints, route length, diameter and total gas volume stay the same. Existing custom pipes are never lengthened automatically; actual short pipes still constrain CFL steps.
- Cache local pipe vertices, normals and indices, shared primitive meshes, and the part-picker icon atlas. Transforms and pressure updates reuse geometry; route/diameter edits rebuild the affected pipe.
Untouched stock imports in machines/ were compared against the previous
importer's canonical output before replacement. User files, including
paralell-twin.machine.toml, were preserved.
Simulation results
Windows GCC RelWithDebInfo, Rusanov, preset density 20 cells/m, 44,100 Hz, 512 warm-up samples and 32,768 measured samples, motor-driven at 3,000 RPM, 35% pedal. Timings include audio synthesis but exclude editor rendering and snapshot collection. Paired native/workshop measurements use the same process; before/after runs have normal timing variation.
| Preset | Workshop before, us/sample | Workshop after | Native after | Workshop cells before / after | Substeps before / after |
|---|---|---|---|---|---|
| Single 450 | 12.61 | 3.55 | 2.89 | 56 / 44 | 4.00 / 1.00 |
| Twin | 16.96 | 6.89 | 6.11 | 67 / 58 | 4.00 / 1.72 |
| Flat6 | 104.44 | 8.79 | 8.43 | 161 / 98 | 12.35 / 1.03 |
| V8 H-pipe | 67.51 | 16.01 | 16.56 | 318 / 175 | 4.09 / 1.00 |
At 6,000 RPM and 70% pedal, flat6 measured 9.31 us/sample and V8 16.11. All benchmark cases reported zero positivity repairs and finite audio. See baseline, after and higher-load results.
These are performance comparisons, not claims of identical combustion or sound. The workshop has explicit metering-body storage, connections and editable calibration; the native scenarios assemble that hardware differently. Arbitrary large or finely meshed custom machines can still exceed the audio budget.
Rendering and playback
Hidden 1440 x 900 OpenGL window, 120 static frames, glFinish, no vsync or
simulation: flat6 fell from 1.40 to 0.70 ms/frame; V8 from 1.77 to 0.96 ms/frame.
This measures CPU/GPU render cost, not the displayed frame rate.
See before and after.
The combined workshop/audio check ran at 60 display frames/s with a held 3,000 RPM shaft, 16 warm-up frames and 120 measured frames per machine:
| Preset | Wall seconds | Simulated seconds | Audio underruns | Buffered samples |
|---|---|---|---|---|
| Flat6 | 2.006 | 2.020 | 0 | 4,096 |
| V8 H-pipe | 2.071 | 2.082 | 0 | 4,096 |
Simulation time includes producer buffering and snapshot timing, so a small offset from wall time is expected. This is a short playback check, not a long session guarantee. Raw output: playback.
Validation and reproduction
All 22 CTest cases passed. Machine tests cover import length/volume preservation, route-knot-independent meshes, a real 5 mm pipe retaining its CFL constraint, explicit fuel sources, cold starting and ECU cutoff. Pump pressure agreed within 1% between 44.1 and 88.2 kHz. Builder checks cover geometry-cache reuse and invalidation, pressure coloring, transforms, deletion/ID reuse and the icon atlas. Editor preview images were visually inspected.
From the repository root after cmake --build --preset windows:
ctest --preset windows -j 8 --output-on-failure
.\out\build\windows-gcc\fluidsim_machine_benchmark.exe 32768 3000 0.35
.\out\build\windows-gcc\fluidsim_machine_benchmark.exe 32768 6000 0.7
.\out\build\windows-gcc\fluidsim_machine_render_benchmark.exe 120
.\out\build\windows-gcc\fluidsim_machine_render_benchmark.exe 120 --play
.\out\build\windows-gcc\fluidsim_machine_builder_tests.exe --preview out/workshop-performance-preview