Function step 

pub fn step(
    peds: &mut [Pedestrian],
    walls: &[WallSegment],
    params: &Params,
    dt: f64,
)

👎Deprecated since 0.0.3:

O(n²) reference path with per-tick heap allocation; use step_scratch (zero-alloc) or step_with_grid (broadphase) instead. See docs/rustsim-crowd.md P1-7.

Free-function step for callers that do not need trait dispatch.

Deprecated. This is the O(n²) reference path retained for numerical comparisons and CPU ↔ CUDA equivalence tests. Production callers should use step_scratch (zero-allocation broadphase hot path) or step_with_grid (broadphase, allocates per call). Keeping step for parity is fine; routing fresh code through it is not, because at N ≥ ~1 000 it scales as O(n²) with per-tick heap allocation. See docs/rustsim-crowd.md P1-7.