FA-86982 / Physics integrator stability / Member archive

Leftover whole steps are carried into the next frame after the step budget · case 02

After a long frame the accumulator keeps backlog and every later frame runs at the budget limit.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

solve(frames, dt, max_frame, max_steps): game loop accumulator. Each frame delta is clamped to max_frame and added; run steps while acc >= dt up to max_steps; if a full dt still remains, whole multiples of dt are dropped (spiral-of-death guard). Return [steps per frame, acc/dt after last frame, dropped time].

Why this case matters

Game and robotics physics loops depend on integrator update order, step control and stabilization terms; a wrong decision point turns a stable simulation into drifting or exploding motion.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
case 0	`[[0, 3, 3], 2.5, 0.0]`	`[[0, 3, 3], 0.5, 0.0625]`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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