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| """Cheap policies a model could imitate without planning. Used to check that a task is hard and that the reward | |
| does not pay for laziness: every task should give these low rewards. | |
| published submit the broken published plan as is (usually infeasible) | |
| naive the stored quick fix: keep slots that work, push the rest (solve.naive_replan) | |
| greedy arrival order, earliest free hour at the nearest section, the crane count that finishes soonest | |
| serial every ship in arrival order, one after another on the first sections, far from any conflict | |
| """ | |
| from __future__ import annotations | |
| from .model import Plan, Task | |
| from .solve import _Ledger, naive_replan | |
| def published(task: Task) -> Plan: | |
| plan = task.planned() | |
| for s in task.ships: | |
| if s.id not in plan: | |
| plan[s.id] = (s.arrival, task.first_section) + ((s.std_cranes,) if task.cranes else ()) | |
| return plan | |
| def greedy(task: Task) -> Plan: | |
| led = _Ledger(task) | |
| plan: Plan = {} | |
| for s in sorted(task.ships, key=lambda s: (s.arrival, s.id)): | |
| anchor = s.planned_section if s.planned_section is not None else task.first_section | |
| positions = sorted(range(task.first_section, task.last_section - s.sections + 2), key=lambda k: (abs(k - anchor), k)) | |
| options = range(s.max_cranes, s.min_cranes - 1, -1) if task.cranes else [None] | |
| h = s.arrival | |
| while True: | |
| best = None | |
| for c in options: | |
| sec = next((k for k in positions if led.fits(s, h, k, c)), None) | |
| if sec is not None: | |
| best = (sec, c) | |
| break | |
| if best: | |
| break | |
| h += 1 | |
| led.add(s, h, best[0], best[1]) | |
| plan[s.id] = (h, best[0]) + ((best[1],) if task.cranes else ()) | |
| return plan | |
| def serial(task: Task) -> Plan: | |
| """Ships one at a time in arrival order on the first sections: valid by construction, very late.""" | |
| led = _Ledger(task) | |
| plan: Plan = {} | |
| t = 0 | |
| for s in sorted(task.ships, key=lambda s: (s.arrival, s.id)): | |
| c = s.std_cranes if task.cranes else None | |
| h = max(t, s.arrival) | |
| while not led.fits(s, h, task.first_section, c): | |
| h += 1 | |
| led.add(s, h, task.first_section, c) | |
| plan[s.id] = (h, task.first_section) + ((c,) if task.cranes else ()) | |
| t = h + 1 | |
| return plan | |
| POLICIES = {"published": published, "naive": naive_replan, "greedy": greedy, "serial": serial} | |