Add streakline post-processing and exp control-matrix batch runners (vorticity + streakline)

README.md

@@ -217,6 +217,31 @@ Tested on Tesla V100-SXM2-16GB (CUDA 12.4):
 | Re100 EsoPull SRT | 384×192 | ~3900 |
 | Re3000 MRT+LES | 384×192 | ~4360 |
 
+### Performance methodology
+
+For a "kernel-dominant" baseline (closest to FluidX3D-style throughput testing),
+use the dedicated script:
+
+```bash
+conda run -n pycuda_3_10 python tests/run_perf_baseline.py \
+  --lattice-model D2Q9 --nx 384 --ny 192 --nz 1 \
+  --steps 4000 --warmup-steps 400 --batch-steps 100
+```
+
+This path times GPU stepping (`stepper.step`) and reports MLUPS and batch latency
+percentiles. By default it avoids host readbacks inside the timed loop.
+
+APIs that trigger device-to-host transfers (DTOH) and can reduce MLUPS:
+
+- `Simulation.get_macroscopic()` / `LBMField.get_macroscopic()` (downloads full DDF)
+- `Simulation.get_ddf()` / `LBMField.download_ddf()`
+- `Simulation.save_checkpoint()` (downloads field/state buffers)
+- Body observation downloads (e.g. `ObjectManager.download_obs_full_async(...)`)
+
+Use `tests/run_perf_baseline.py` switches (`--macro-every`, `--ddf-every`,
+`--checkpoint-every`, `--obs-every`) to quantify each overhead path against the
+pure-step baseline.
+
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