FA-67539 / Elevator dispatch scheduling / Member archive

Hall call ETA with intermediate stops: direction mirroring · case 04

ETAs for down-travelling cars count the wrong stops.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

A moving car at floor with direction and car stops estimates its arrival at a hall call (target, call direction). Work in the car direction (mirror floors for down). If the target is strictly ahead and the call is in the car direction, the car goes straight there, stopping at stops strictly between. Otherwise it runs to the farthest of its stops ahead and the target, reverses and returns to the target, stopping at every stop ahead plus stops strictly between target and floor behind. A stop at the target floor is not extra. ETA = floors travelled * per_floor_s + stops * stop_s.

Why this case matters

Lift group controllers make these decisions many times per minute; a wrong answer strands passengers, wastes trips or overrides a safety rule.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression: call behind a down car	`78`	`30`	Failed

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