Throughput

Steps per second for a vmapped, jitted, scanned rollout: the way an RL loop actually drives these environments, not one Python-level step at a time. Reproduce with:

uv run python -m target_gym.benchmark_speed --batch 4096 --steps 500

Measured on arm64 CPU, Darwin, single process, no GPU.

These are not properties of the plants. They move with the machine and with the batch size, which is why they are measured here rather than claimed in the fifteen PHYSICS.md contracts, where every other number is a fact about the process being modelled. Nothing in CI checks them, because a check that fails on somebody else's laptop is worse than no check.

environment	batch 4096	batch 256
first_order	694.72 M	773.12 M
cstr	201.55 M	176.35 M
four_tank	111.44 M	108.26 M
hvac	12.75 M	12.39 M
boiler_drum	11.89 M	10.85 M
battery	11.31 M	9.23 M
wind_turbine	11.23 M	12.44 M
glass_furnace	4.10 M	3.34 M
ph_neutralization	3.97 M	3.77 M
plane	2.13 M	1.39 M
plane_energy	2.13 M	1.39 M
plane_sine	2.13 M	1.41 M
plane3d_heading	1.55 M	1.00 M
plane3d_figure8	1.50 M	0.99 M
cement_kiln	1.19 M	0.61 M
plane3d_circle	1.18 M	0.98 M
plane3d_racetrack	1.18 M	0.97 M
reactor	1.17 M	1.30 M
distillation	0.82 M	0.38 M
patrol_bearing_only	0.64 M	0.54 M
patrol	0.62 M	0.53 M

What this means for RL

The protocol's largest sample budget is 1e7 environment steps. At the slowest environment here that is about 16 seconds of environment time; at the fastest it is under a millisecond. Network forward and backward passes dominate any learning loop by two to three orders of magnitude, so the environment is never the bottleneck at these budgets, and none of the twenty-one is unfit on speed.

The spread is arithmetic per step, not anything fixable. The distillation column integrates 41 states through 16 RK4 substeps, and its contract establishes that 16 is a stability requirement rather than a refinement. Patrol integrates two complete 3D aircraft. The cement kiln carries 16 axial zones of 4 states plus a sequential gas sweep. The three-order-of-magnitude leaders are one to four states with a single substep.

Which environment is slowest depends on the batch size: patrol at 4096, the distillation column at 256. Two contracts used to claim the title outright, and both were wrong at one of the two batch sizes.