FA-65407 / Ecological population dynamics / Member archive

Lotka-Volterra predator-prey Euler integration: simultaneous derivative state · case 02

Predator growth responds to prey that were already updated in the same step.

Member previewVariant 2 · 3 implementations · 7 checks per implementation

Case contract

dx = alpha*x - beta*x*y, dy = delta*x*y - gamma*y evaluated from the same start-of-step state; Euler update with each population floored at 0; return [path of [x,y] rounded 4 including start, coexistence equilibrium [gamma/delta, alpha/beta] rounded 4 or None when beta or delta is not positive].

Why this case matters

Population projections set harvest quotas, conservation status and pest-control timing; a wrong update order, boundary or rate conversion silently changes management advice.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression: hare and lynx	`[[[40.0, 9.0], [38.4, 10.278], [36.3732, 11.6333], [33.9605, 13.027], [31.2345, 14.4101], [28.2953, 15.7283], [25.2597, 16.9284]], [10.0, 5.0]]`	`[[[40.0, 9.0], [38.4, 10.35], [36.3456, 11.8197], [33.8669, 13.3767], [31.03, 14.973], [27.9354, 16.5474], [24.7096, 18.0313]], [10.0, 5.0]]`	Failed

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