feat(harness): checkpoint 存 unit_id 序列,断点续跑孪生对不拆

核心算法保真 #3(断点续跑):checkpoint 从逐题 question_id 改为存 unit_id
序列(孪生对折叠为单个 unit_id),恢复时 build_units + 按完整 unit 展开,
续跑后 pair 两成员同进同出、绝不被劈开。

- _batch_unit_ids/_batch_from_ids 对称折叠/展开,保序去重,纯非 AR 下
  unit_id==question_id、与旧逐题序列逐字节一致。
- momentum 采样抽取为 _sample_momentum_candidates 纯函数,docstring 显式
  记录 Phase 1 设计偏差:仅保证纯非 AR byte-identical,混格 momentum 不保证。
- 新增 test_checkpoint_pair(unit_id 落盘往返、pair 不拆)与
  test_non_ar_byte_identical(pools→batching→checkpoint→momentum 端到端黄金)。
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"""断点续跑 checkpoint 的 unit_id 粒度契约集成测试(Task 10)。
覆盖三条铁律:
- checkpoint 存 **unit_id 序列**而非逐题 question_id(孪生对折叠为单个 unit_id);
- 续跑恢复以 **完整 unit** 展开(pair 两成员同进同出,绝不被劈开);
- 真实经 write_checkpoint → load_checkpoint 落盘往返后,unit_id 序列无损存活、
重建的 batch 与原 batch 逐字节一致(core 算法保真 #3 断点续跑)。
"""
from __future__ import annotations
from dataclasses import dataclass, field
from typing import TYPE_CHECKING
from app.harness.batching import build_batches
from app.harness.checkpoint import load_checkpoint, write_checkpoint
from app.harness.pools import Pools
from app.harness.question_units import build_units, validate_units
from app.harness.runner import _batch_from_ids, _batch_unit_ids
from core.types import GeneratedQuestion
if TYPE_CHECKING:
from pathlib import Path
# ---------------------------------------------------------------------------
# 辅助构造
# ---------------------------------------------------------------------------
def _make_single(qid: str, task_type: str = "RETRIEVAL", video_id: str = "v1") -> GeneratedQuestion:
"""构造最小 single 题目。"""
return GeneratedQuestion(
question_id=qid,
video_id=video_id,
task_type=task_type,
question=f"q_{qid}",
options=("A. a", "B. b", "C. c", "D. d"),
answer="A",
source_nodes=("n1",),
difficulty="medium",
question_role="single",
)
def _make_pair(
pair_id: str, task_type: str = "AR", video_id: str = "v1"
) -> tuple[GeneratedQuestion, GeneratedQuestion]:
"""构造一个孪生对(original + mirror),共享 pair_id / flip_axis。"""
common = {
"video_id": video_id,
"task_type": task_type,
"question": "?",
"options": ("A. a", "B. b", "C. c", "D. d"),
"answer": "A",
"source_nodes": ("n1",),
"difficulty": "medium",
"pair_id": pair_id,
"flip_axis": "before_after",
}
original = GeneratedQuestion(
question_id=f"{pair_id}_o", question_role="pair_original", **common
)
mirror = GeneratedQuestion(question_id=f"{pair_id}_m", question_role="pair_mirror", **common)
return original, mirror
def _pools_with(diagnosis: list[GeneratedQuestion]) -> Pools:
"""用给定诊断池构造最小 Pools(其余池置空,_batch_from_ids 只读 diagnosis)。"""
return Pools(
diagnosis=diagnosis,
validation=[],
test=[],
baseline_run_id="baseline",
baseline_val_accuracy=0.0,
correctness={q.question_id: False for q in diagnosis},
)
# ---------------------------------------------------------------------------
# checkpoint 落盘所需的最小 _TrainState / RunConfig 替身
# ---------------------------------------------------------------------------
@dataclass
class _FakeState:
"""serialize_state 只读的可持久化字段(本测试用空累加包即可)。"""
correctness: dict[str, bool] = field(default_factory=dict)
eval_prev_acc: float = 0.0
eval_prev_run_id: str = "run-0"
baseline_skills_version: str = "v1"
baseline_prompts_version: str = "v1"
steps_since_best_improved: int = 0
epoch_start_skills: str = "v1"
changed_task_types_this_epoch: set[str] = field(default_factory=set)
rejected_buffer: dict = field(default_factory=dict)
system_packs: list = field(default_factory=list)
tool_packs: list = field(default_factory=list)
probations: dict = field(default_factory=dict)
gate_cooldown: dict = field(default_factory=dict)
gate_epoch_observed: dict = field(default_factory=dict)
@dataclass(frozen=True)
class _FakeConfig:
"""compute_fingerprint 读取的结构性 + 决策性字段。"""
batch_size: int = 4
min_class_per_batch: int = 2
epochs: int = 3
diag_size: int = 30
val_size: int = 50
batch_correct_ratio: float = 0.0
edit_budget_start: int = 6
edit_budget_end: int = 3
early_stop_patience: int = 3
use_slow_momentum: bool = True
skill_update_mode: str = "patch"
appendix_consolidate_threshold: int = 10
momentum_samples: int = 20
gate_e_confirm: float = 20.0
gate_e_provisional: float = 6.0
gate_w_net_min: int = 2
gate_delta_min: float = 0.02
gate_lambda_dir: float = -3.0
gate_e_rollback: float = 10.0
gate_block: int = 4
gate_n_max: int = 40
gate_p_low: float = 0.1
gate_p_high: float = 0.9
gate_probe_quota: float = 0.2
gate_gamma_decay: float = 0.9
gate_cooldown_steps: int = 2
gate_guard_err: float = 0.3
# ---------------------------------------------------------------------------
# checkpoint 存 unit_id 序列(孪生对折叠为单个 unit_id)
# ---------------------------------------------------------------------------
class TestCheckpointStoresUnitIds:
"""一个含孪生对的 batchcheckpoint 序列应折叠为 unit_idpair 只记一次)。"""
def test_pair_folds_to_single_unit_id(self) -> None:
po, pm = _make_pair("pA")
s1, s2 = _make_single("s1"), _make_single("s2")
batch = [s1, po, pm, s2] # pair 两成员相邻
unit_ids = _batch_unit_ids(batch)
# 4 题折叠为 3 个 units1 / pA(pair) / s2
assert unit_ids == ["s1", "pA", "s2"]
# 逐题 question_id 序列(旧行为)会含 4 项且把 pair 拆成两条
assert [q.question_id for q in batch] == ["s1", "pA_o", "pA_m", "s2"]
def test_pure_single_unit_ids_equal_question_ids(self) -> None:
"""纯 single batch 的 unit_id 序列与逐题 question_id 序列逐字节一致。"""
batch = [_make_single(f"s{i}") for i in range(5)]
assert _batch_unit_ids(batch) == [q.question_id for q in batch]
# ---------------------------------------------------------------------------
# 恢复以完整 unit 展开:pair 不拆
# ---------------------------------------------------------------------------
class TestResumeExpandsFullUnit:
"""按 unit_id 序列恢复时,孪生对整体展开、绝不被劈开。"""
def test_pair_not_split_on_resume(self) -> None:
po, pm = _make_pair("pA")
s1, s2 = _make_single("s1"), _make_single("s2")
batch = [s1, po, pm, s2]
# 诊断池顺序故意与 batch 不同,验证恢复以池折叠的 unit 为准
pools = _pools_with([s2, pm, s1, po])
unit_ids = _batch_unit_ids(batch)
restored = _batch_from_ids(pools, unit_ids)
# 逐字节一致(顺序保留)
assert [q.question_id for q in restored] == ["s1", "pA_o", "pA_m", "s2"]
# 恢复后可无损重建为完整孪生对单元
units = validate_units(build_units(restored))
pair_units = [u for u in units if u.kind == "pair"]
assert len(pair_units) == 1
assert pair_units[0].unit_id == "pA"
assert pair_units[0].size == 2
def test_roundtrip_preserves_order_mixed(self) -> None:
"""混格 batch 经 unit_id 折叠 → 展开 round-trip 逐字节还原原顺序。"""
po, pm = _make_pair("pA")
qo, qm = _make_pair("pB")
singles = [_make_single(f"s{i}") for i in range(3)]
batch = [singles[0], po, pm, singles[1], qo, qm, singles[2]]
pools = _pools_with(list(batch))
restored = _batch_from_ids(pools, _batch_unit_ids(batch))
assert [q.question_id for q in restored] == [q.question_id for q in batch]
def test_missing_unit_id_raises(self) -> None:
"""checkpoint 引用了诊断池不存在的 unit_id 时硬失败(防静默兜底)。"""
pools = _pools_with([_make_single("s1")])
try:
_batch_from_ids(pools, ["s1", "ghost"])
except KeyError:
return
raise AssertionError("引用缺失 unit_id 应触发 KeyError")
# ---------------------------------------------------------------------------
# 真实落盘往返:write_checkpoint → load_checkpoint → 重建 batch
# ---------------------------------------------------------------------------
class TestCheckpointPersistenceRoundtrip:
"""unit_id 序列经真实 checkpoint.json 原子写/读回后无损、重建逐字节一致。"""
def test_persisted_unit_ids_rebuild_batches(self, tmp_path: Path) -> None:
po, pm = _make_pair("pA")
singles = [_make_single(f"s{i}", task_type="RETRIEVAL") for i in range(6)]
items = [*singles, po, pm]
correctness = {q.question_id: False for q in items}
batches, _ = build_batches(items, correctness, batch_size=4, min_class_per_batch=2, seed=7)
pools = _pools_with(list(items))
# 存 unit_id 序列(train() 落盘路径)
epoch_batches = [_batch_unit_ids(b) for b in batches]
write_checkpoint(
tmp_path,
state=_FakeState(correctness=correctness),
epoch=1,
step_completed=0,
phase="in_epoch",
global_step=1,
total_steps=len(batches),
version_snapshot={"skills": "skills/v1", "prompts": "prompts/v1"},
epoch_batches=epoch_batches,
config=_FakeConfig(),
)
ckpt = load_checkpoint(tmp_path)
assert ckpt is not None
rebuilt = [_batch_from_ids(pools, ids) for ids in ckpt["epoch_batches"]]
# 落盘往返后逐批逐字节还原
assert [[q.question_id for q in b] for b in rebuilt] == [
[q.question_id for q in b] for b in batches
]
# 含孪生对的批次恢复后 pair 仍成对
for b in rebuilt:
for u in validate_units(build_units(b)):
if u.kind == "pair":
assert u.size == 2