File size: 28,381 Bytes
09c13a5
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
"""Letter readout of a stock chat model for the Decision Index. Nothing is generated.

The baseline prompt is the "chat layout" of decider-ai 1.6.0 (Apache-2.0, github.com/Mapika/decider), which is how the
board entry "Decider chat · Gemma-4-31B" reads the stock model. One row per question:

    <chat template head>Context:\n<state>\n\nQuestion: <instructions>\nOptions:\n(A) ...\n(B) ...<template tail, thinking off>Answer: (

The answer is read at the final " (": the last hidden state there is multiplied by the output-embedding rows of the
labels of the question's options, in float32, and the result goes through a softmax at a temperature set by the number
of options. These are the logits before Gemma's final soft cap (30 * tanh(x / 30)); the capped logits the model returns
squeeze every confident answer into the same narrow band below 30. Up to 10 options are labelled A..J; above that every
option gets its own single-token label (A..Z, then two-letter strings), up to 255.

By default the state is read once per request and the request's questions are read side by side after it in one pass
(pack_questions); each question sees only the state and itself, so this equals one full row per question up to bf16
rounding. With read_twice the user turn is written twice, as shisa-ai/shisa-de-2 does:

    Context:\n<state>\n\nQuestion: ...\nOptions: ...\n\nRead the same input again before answering:\nContext:\n<state>\n\nQuestion: ...\nOptions: ...

so the second copy of the state is read with the question and its options already in view. Reading twice costs about
twice the tokens, so it can be limited: twice_max_tokens reads twice only requests of at most that many tokens read once
(state plus all its questions), and reread_below re-reads, written twice, the questions of the other requests whose most
likely option has a probability below that value after the first read; the state stays cached between the two reads. A
row that written twice would pass the token limit is read once.

    python -m decision_index run --engine jevlab.reader:Reader --rows sample.jsonl.gz --out runs/reader-sample
"""
import json
import math
import string

from decision_index.engines.base import Engine, Unsupported

LETTERS = "ABCDEFGHIJ"
MAX_OPTIONS = 255
ANNOTATE_MIN = 8
NOUL_WITHOUT_INSTRUCTIONS = "Which answer fits the context?"
READ_AGAIN = "\n\nRead the same input again before answering:\n"
QUESTIONS_HEAD = "Questions that will be asked about the context:\n"
QUESTIONS_ITEM = "- "
LAYOUTS = ("decider", "header")
SENTINEL = "@@JEVLAB_USER_CONTENT@@"
THINKING_BLOCKS = (("<think>\n", "</think>\n\n"), ("<think>", "</think>\n\n"), ("<|channel>thought\n", "<channel|>"))


def _txt(v):
    return v if isinstance(v, str) else json.dumps(v, ensure_ascii=False)


def _flag(v):
    return v.strip().lower() in ("1", "true", "yes", "on") if isinstance(v, str) else bool(v)


def annotate_indices(x, min_len=ANNOTATE_MIN):
    """Write each element's position into long arrays, so a question naming `records[47]` is a lookup, not a count."""
    if isinstance(x, list):
        if len(x) >= min_len:
            return [{"_index": i, **annotate_indices(v, min_len)} if isinstance(v, dict) else {"_index": i, "value": annotate_indices(v, min_len)} for i, v in enumerate(x)]
        return [annotate_indices(v, min_len) for v in x]
    if isinstance(x, dict):
        return {k: annotate_indices(v, min_len) for k, v in x.items()}
    return x


def render_state(state):
    return state if isinstance(state, str) else json.dumps(annotate_indices(state), ensure_ascii=False)


def render_question(q):
    """-> (question text, option texts, option keys). A noul question is the two options no/yes, keyed False/True."""
    kind, crit, raw = q["type"], q.get("criteria"), q.get("instructions", "")
    if kind == "choice":
        if isinstance(crit, (list, tuple)):
            crit = {str(c): None for c in crit}
        if not isinstance(crit, dict) or not 2 <= len(crit) <= MAX_OPTIONS:
            raise Unsupported(f"options per choice: a map of 2..{MAX_OPTIONS} options is required")
        keys = list(crit)
        return _txt(raw), [k if crit[k] in (None, "") else f"{k}: {_txt(crit[k])}" for k in keys], keys
    if kind == "noul":
        crit = crit if isinstance(crit, dict) else {}
        no, yes = crit.get("false", crit.get(False)), crit.get("true", crit.get(True))
        text = NOUL_WITHOUT_INSTRUCTIONS if raw in (None, "") else _txt(raw)
        return text, ["no" if no in (None, "") else f"no: {_txt(no)}", "yes" if yes in (None, "") else f"yes: {_txt(yes)}"], [False, True]
    raise Unsupported("Unsupported question type " + str(kind))


class Layout:
    """Token ids of the prompt rows. Needs only the tokenizer."""

    def __init__(self, tok, system=None):
        if not getattr(tok, "chat_template", None):
            raise ValueError("the tokenizer has no chat template")
        self.tok, self.system = tok, system or None
        kw = {"enable_thinking": False} if "enable_thinking" in tok.chat_template else {}
        turns = ([{"role": "system", "content": self.system}] if self.system else []) + [{"role": "user", "content": SENTINEL}]
        head, tail = tok.apply_chat_template(turns, tokenize=False, add_generation_prompt=True, **kw).split(SENTINEL)
        if self.system and self.system not in head:
            raise ValueError("the chat template dropped the system turn")
        for opened, closed in THINKING_BLOCKS:
            if tail.endswith(opened):
                tail += closed
        self.head_text, self.tail_text = head, tail
        self.head, self.tail = self._enc(head), self._enc(tail)
        self.answer = self._enc("Answer: (")
        self.open = self._enc("\n(")
        names = list(string.ascii_uppercase) + [a + b for a in string.ascii_uppercase for b in string.ascii_uppercase]
        single = [(n, t[0]) for n, t in ((n, self._enc(n)) for n in names) if len(t) == 1][:MAX_OPTIONS]
        self.labels, self.label_ids = [n for n, _ in single], [i for _, i in single]
        if len(self.label_ids) != MAX_OPTIONS or len(set(self.label_ids)) != MAX_OPTIONS:
            raise ValueError("the tokenizer does not have 255 distinct single-token labels")
        # the labels must be what the model would write next at the answer slot, and the slot must not merge with the template
        for n, i in single[: len(LETTERS)]:
            if self._enc("Answer: (" + n) != self.answer + [i]:
                raise ValueError(f"the label {n!r} is not one token after 'Answer: ('")
        if self._enc(tail + "Answer: (") != self.tail + self.answer:
            raise ValueError("the chat template tail merges with the answer slot")

    def _enc(self, text):
        return self.tok.encode(text, add_special_tokens=False)

    @staticmethod
    def listing(texts):
        """The header layout's list of every question of the request, placed before the state."""
        return QUESTIONS_HEAD + "\n".join(QUESTIONS_ITEM + t for t in texts) + "\n\n"

    def context(self, state, texts=None):
        """Ids up to the end of the state. With `texts` (the request's question texts) the header layout: the list of
        questions, then the state, each part encoded on its own as wcole3/jev-brain builds it."""
        ids = self.head + (self._enc(self.listing(texts)) if texts is not None else [])
        return ids + self._enc("Context:\n" + render_state(state))

    def again(self, state, texts=None):
        """Ids that start the second copy of the user turn, up to the end of its state."""
        return self._enc(READ_AGAIN + (self.listing(texts) if texts is not None else "") + "Context:\n" + render_state(state))

    def question(self, text, options, again=None):
        """Ids after the context: the question, its labelled options, the template tail and the answer slot. With `again`
        (from again()), the user turn is written a second time before the tail."""
        ids = self._enc(f"\n\nQuestion: {text}\nOptions:")
        if len(options) <= len(LETTERS):
            ids += self._enc("".join(f"\n({LETTERS[j]}) {o}" for j, o in enumerate(options)))
        else:
            for j, o in enumerate(options):
                ids += self.open + [self.label_ids[j]] + self._enc(f") {o}")
        if again:
            ids = ids + again + ids
        return ids + self.tail + self.answer


class Reader(Engine):
    name = "jevlab-reader"
    latency = "In-process request wall time including prompt construction and reuse of the state's KV cache across the questions of one request; excludes model loading."

    def __init__(self, model="google/gemma-4-31B-it", revision="842da3794eaa0b77d5f08bae87a17459d91ff475", device=None, dtype="bfloat16", temperature=10.124, temperature_log_slope=-1.633,
                 max_tokens=32768, chunk_tokens=8192, cache_prefix=False, cudnn_sdp=False, pack_questions=True, pack_tokens=4096, read_twice=False, twice_max_tokens=0, reread_below=0.0, reverse_below=0.0, layout="decider", attn_block=512, **options):
        super().__init__(**options)
        import torch
        from transformers import AutoModelForCausalLM, AutoTokenizer

        self.torch = torch
        self.device = device or ("cuda" if torch.cuda.is_available() else "cpu")
        # decider-ai reports that on Blackwell with torch 2.14 the cuDNN attention backend returns wrong output when a suffix
        # attends to a cached prefix (engine.set_attention_backend_policy). Our own runs came out identical with it on and
        # off, so this is a precaution, not a measured fix.
        if not cudnn_sdp and hasattr(torch.backends.cuda, "enable_cudnn_sdp"):
            torch.backends.cuda.enable_cudnn_sdp(False)
        self.tok = AutoTokenizer.from_pretrained(model, revision=revision)
        self.layout = Layout(self.tok)
        self.model = AutoModelForCausalLM.from_pretrained(model, revision=revision, dtype=getattr(torch, dtype)).to(self.device).eval()
        self.decoder = self.model.model                                       # everything below the output layer
        head = self.model.get_output_embeddings()
        if head.bias is not None:
            raise ValueError("the output layer has a bias; the label readout assumes it has none")
        self.label_rows = head.weight.detach()[torch.tensor(self.layout.label_ids, device=self.device)].float()
        self.attn_block = int(attn_block)
        if self.attn_block > 0:
            from jevlab.attention import use_blocked_attention
            use_blocked_attention(self.model, self.attn_block)
        self.model_id = model
        # T(n) = temperature + temperature_log_slope * ln(n options). The defaults are the fit published for the board entry
        # "Decider chat · Gemma-4-31B" (Mapika/decision-index-results README); they are here to reproduce that entry.
        self.temperature, self.temperature_log_slope = float(temperature), float(temperature_log_slope)
        self.limit = int(max_tokens)
        self.chunk = int(chunk_tokens)
        self.cache_prefix = _flag(cache_prefix)
        self.pack, self.pack_tokens = _flag(pack_questions), int(pack_tokens)
        self.read_twice = _flag(read_twice)
        self.twice_max_tokens, self.reread_below = int(twice_max_tokens), float(reread_below)
        self.reverse_below = float(reverse_below)
        if layout not in LAYOUTS:
            raise ValueError(f"layout must be one of {LAYOUTS}, not {layout!r}")
        self.header = layout == "header"
        cfg = self.model.config.get_text_config()
        self.layer_types, self.window = set(cfg.layer_types), getattr(cfg, "sliding_window", None)
        self.cache, self.cached_ids = None, []
        self.provenance = {
            "kind": "inference technique",
            "repo": model,
            "revision": revision or getattr(self.model.config, "_commit_hash", None),
            "device": self.device,
            "dtype": dtype,
            "temperature": self.temperature,
            "temperature_log_slope": self.temperature_log_slope,
            "max_row_tokens": self.limit,
            "cudnn_sdp": bool(cudnn_sdp),
            "pack_questions": self.pack,
            "read_twice": self.read_twice,
            "twice_max_tokens": self.twice_max_tokens,
            "reread_below": self.reread_below,
            "reverse_below": self.reverse_below,
            "layout": "header" if self.header else "decider",
            "attention": f"sdpa in query blocks of {self.attn_block}, each over the span of keys its mask allows" if self.attn_block > 0 else "sdpa",
            "policy": ("The state is preceded by the list of every question of the request ('Questions that will be asked about the context:'), "
                       "the header layout of wcole3/jev-brain. " if self.header else "")
                      + "One row per question in the model's chat template with thinking off, ending at 'Answer: ('; the last hidden state there times the "
                      "output-embedding rows of the option labels (float32, before the final soft cap) goes through a softmax. Options keep the request's "
                      "order. Rows above the token limit are refused, never cut."
                      + (" The user turn (state, question, options) is written twice, joined by 'Read the same input again before answering:'"
                         + (f", in requests of at most {self.twice_max_tokens} tokens read once" if self.twice_max_tokens > 0 else "") + "." if self.read_twice else "")
                      + (f" Questions of the other requests whose most likely option has probability below {self.reread_below} are read again, written twice "
                         "the same way, after the first read." if self.reread_below > 0 else "")
                      + (f" A question whose most likely option then has probability below {self.reverse_below} is read once more with its options in "
                         "reverse order, and the two distributions are averaged." if self.reverse_below > 0 else "")
                      + (" The state is read once per request; the questions of the request are read side by side after it in one pass, each seeing only "
                         "the state and itself." if self.pack else ""),
        }
        if self.pack:
            self.latency = "In-process request wall time including prompt construction; the state is read once and the request's questions are read together after it; excludes model loading."
        elif not self.cache_prefix:
            self.latency = "In-process request wall time including prompt construction; every question row is read in full; excludes model loading."

    def runtime(self):
        torch = self.torch
        import transformers

        info = {"torch": torch.__version__, "transformers": transformers.__version__, "device": self.device}
        if self.device == "cuda":
            info.update(cuda=torch.version.cuda, gpu=torch.cuda.get_device_name())
        return info

    def synchronize(self):
        if self.device == "cuda":
            self.torch.cuda.synchronize()

    def reset_cache(self):
        self.cache, self.cached_ids = None, []

    def _forward(self, ids, chunk):
        """Run `ids`, reusing the cached prefix it shares with the previous row. -> (hidden state at the last position, cached prefix length)."""
        torch = self.torch
        from transformers import DynamicCache

        p = 0
        if self.cache_prefix and self.cache is not None:
            n = min(len(ids) - 1, len(self.cached_ids))
            while p < n and ids[p] == self.cached_ids[p]:
                p += 1
        if p == 0:
            self.cache = DynamicCache()
        elif len(self.cached_ids) > p:
            self.cache.crop(p - len(self.cached_ids))
        self.cached_ids = ids[:p]
        with torch.inference_mode():
            for s in range(p, len(ids), chunk):
                piece = ids[s:s + chunk]
                out = self.decoder(input_ids=torch.tensor([piece], device=self.device), attention_mask=torch.ones(1, s + len(piece), dtype=torch.long, device=self.device),
                                   past_key_values=self.cache, use_cache=True)
                self.cache = out.past_key_values
                self.cached_ids = ids[:s + len(piece)]
        return out.last_hidden_state[0, -1], p

    def _pack_masks(self, p, lengths):
        """Masks for questions laid side by side after a cached prefix of p tokens. Each question token sees the prefix and
        the earlier tokens of its own question, at the positions it would have in its own row; on sliding-window layers only
        keys less than `window` positions back, the rule transformers applies to a full row (masking_utils.sliding_window_overlay)."""
        torch, dev = self.torch, self.device
        own = torch.repeat_interleave(torch.arange(len(lengths), device=dev), torch.tensor(lengths, device=dev))
        qpos = p + torch.cat([torch.arange(m, device=dev) for m in lengths])
        kpos = torch.cat([torch.arange(p, device=dev), qpos])
        kown = torch.cat([torch.full((p,), -1, device=dev), own])
        allowed = (kown[None, :] == -1) | ((kown[None, :] == own[:, None]) & (kpos[None, :] <= qpos[:, None]))
        masks = {}
        for t in self.layer_types:
            if t == "full_attention":
                masks[t] = allowed[None, None]
            elif t == "sliding_attention":
                masks[t] = (allowed & (qpos[:, None] - kpos[None, :] < self.window))[None, None]
            else:
                raise ValueError(f"no packed mask for layer type {t!r}")
        return masks, qpos

    def _packed(self, p, pieces):
        """Hidden states at the last token of each piece, the pieces read side by side after the cached prefix of p tokens."""
        torch = self.torch
        lengths = [len(x) for x in pieces]
        masks, qpos = self._pack_masks(p, lengths)
        ids = torch.tensor([[t for x in pieces for t in x]], device=self.device)
        ends = torch.tensor(lengths, device=self.device).cumsum(0) - 1
        try:
            with torch.inference_mode():
                out = self.decoder(input_ids=ids, attention_mask=masks, position_ids=qpos[None], past_key_values=self.cache, use_cache=True)
            return out.last_hidden_state[0, ends]
        finally:
            extra = self.cache.get_seq_length() - p
            if extra > 0:
                self.cache.crop(-extra)

    def _joint(self, ctx, pieces):
        """Hidden states at the last token of each piece, the state and all pieces read in one pass: the state causally,
        each piece after it seeing the state and itself. The state's keys and values stay in the cache afterwards."""
        torch, dev = self.torch, self.device
        from transformers import DynamicCache

        p, lengths = len(ctx), [len(x) for x in pieces]
        own = torch.cat([torch.full((p,), -1, device=dev), torch.repeat_interleave(torch.arange(len(lengths), device=dev), torch.tensor(lengths, device=dev))])
        pos = torch.cat([torch.arange(p, device=dev)] + [p + torch.arange(m, device=dev) for m in lengths])
        allowed = (pos[None, :] <= pos[:, None]) & ((own[None, :] == -1) | (own[None, :] == own[:, None]))
        masks = {}
        for t in self.layer_types:
            if t == "full_attention":
                masks[t] = allowed[None, None]
            elif t == "sliding_attention":
                masks[t] = (allowed & (pos[:, None] - pos[None, :] < self.window))[None, None]
            else:
                raise ValueError(f"no packed mask for layer type {t!r}")
        ids = torch.tensor([ctx + [t for x in pieces for t in x]], device=dev)
        ends = p + torch.tensor(lengths, device=dev).cumsum(0) - 1
        self.cache, self.cached_ids = DynamicCache(), []
        with torch.inference_mode():
            out = self.decoder(input_ids=ids, attention_mask=masks, position_ids=pos[None], past_key_values=self.cache, use_cache=True)
        extra = self.cache.get_seq_length() - p
        if extra > 0:
            self.cache.crop(-extra)
        self.cached_ids = list(ctx)
        return out.last_hidden_state[0, ends]

    def _extend(self, p, piece, chunk):
        """Hidden state at the last token of one long piece, read in chunks after the cached prefix of p tokens."""
        torch = self.torch
        try:
            with torch.inference_mode():
                for s in range(0, len(piece), chunk):
                    part = piece[s:s + chunk]
                    out = self.decoder(input_ids=torch.tensor([part], device=self.device), attention_mask=torch.ones(1, p + s + len(part), dtype=torch.long, device=self.device),
                                       past_key_values=self.cache, use_cache=True)
            return out.last_hidden_state[0, -1]
        finally:
            extra = self.cache.get_seq_length() - p
            if extra > 0:
                self.cache.crop(-extra)

    def packed_label_logits(self, ctx, pieces, ns, reuse=False):
        """float32 label logits of every question of a request: the state once, then the questions in packs of about
        pack_tokens tokens. A question longer than that is read on its own, in chunks. A request of at most pack_tokens
        tokens in all is read in one pass. With reuse, a state still cached from the first read of the same request is not
        read again."""
        budget = self.pack_tokens
        while True:
            try:
                if not reuse and not self.cache_prefix and len(ctx) + sum(map(len, pieces)) <= budget:
                    hidden = self._joint(ctx, pieces)
                    return [(self.label_rows[:n] @ h.float()).cpu() for h, n in zip(hidden, ns)], 0
                if reuse and self.cache is not None and self.cached_ids == ctx and self.cache.get_seq_length() == len(ctx):
                    p0 = len(ctx)
                else:
                    _, p0 = self._forward(ctx, self.chunk)
                p = len(ctx)
                hidden, group, size = {}, [], 0
                for i, piece in enumerate(pieces):
                    if len(piece) > budget:
                        hidden[i] = self._extend(p, piece, budget)
                        continue
                    if group and size + len(piece) > budget:
                        hidden.update(zip(group, self._packed(p, [pieces[j] for j in group])))
                        group, size = [], 0
                    group.append(i)
                    size += len(piece)
                if group:
                    hidden.update(zip(group, self._packed(p, [pieces[j] for j in group])))
                return [(self.label_rows[:n] @ hidden[i].float()).cpu() for i, n in enumerate(ns)], p0
            except self.torch.OutOfMemoryError:
                self.reset_cache()
                if self.device == "cuda":
                    self.torch.cuda.empty_cache()
                if budget <= 256:
                    raise
                budget //= 2
            except Exception:
                self.reset_cache()
                raise

    def label_logits(self, ids, n):
        """float32 logits (before the soft cap) of the first n labels at the answer slot of one row."""
        torch = self.torch
        chunk = self.chunk
        while True:
            try:
                hidden, p = self._forward(ids, chunk)
                return (self.label_rows[:n] @ hidden.float()).cpu(), p
            except torch.OutOfMemoryError:
                self.reset_cache()
                if self.device == "cuda":
                    torch.cuda.empty_cache()
                if chunk <= 512:
                    raise
                chunk //= 2
            except Exception:
                self.reset_cache()
                raise

    def _read(self, ctx, pieces, ns, reuse=False):
        """-> [(float32 label logits, cached prefix tokens)] for the pieces after ctx."""
        if self.pack:
            logits, p0 = self.packed_label_logits(ctx, pieces, ns, reuse)
            return [(x, p0 if i == 0 else len(ctx)) for i, x in enumerate(logits)]
        return [self.label_logits(ctx + piece, n) for piece, n in zip(pieces, ns)]

    def _probs(self, logits, n):
        t = max(self.temperature + self.temperature_log_slope * math.log(n), 0.05)
        return self.torch.softmax(logits.double() / t, -1).tolist()

    def __call__(self, state, questions):
        rendered = [(key, q["type"], *render_question(q)) for key, q in questions.items()]
        texts = [text for _, _, text, _, _ in rendered] if self.header else None
        ctx = self.layout.context(state, texts)
        again = self.layout.again(state, texts) if self.read_twice or self.reread_below > 0 else None
        rows = []
        for key, kind, text, options, keys in rendered:
            rows.append((key, kind, self.layout.question(text, options), self.layout.question(text, options, again) if again else None, keys))
        # a request whose rows written twice would pass the token limit is read once
        fits = [again is not None and len(ctx) + len(twice) <= self.limit for _, _, _, twice, _ in rows]
        once_tokens = len(ctx) + sum(len(once) for _, _, once, _, _ in rows)
        whole = self.read_twice and all(fits) and (self.twice_max_tokens <= 0 or once_tokens <= self.twice_max_tokens)
        first = [twice if whole else once for _, _, once, twice, _ in rows]
        for piece in first:
            if len(ctx) + len(piece) > self.limit:
                raise Unsupported(f"maximum context length: a row of {len(ctx) + len(piece)} tokens exceeds the declared limit of {self.limit}")
        ns = [len(keys) for *_, keys in rows]
        read = self._read(ctx, first, ns)
        pieces = list(first)
        reread = self.reread_below > 0 and not whole
        unsure = [i for i, ((logits, _), n) in enumerate(zip(read, ns)) if reread and fits[i] and max(self._probs(logits, n)) < self.reread_below]
        firsts = {}
        if unsure:
            again_read = self._read(ctx, [rows[i][3] for i in unsure], [ns[i] for i in unsure], reuse=True)
            for i, (logits, _) in zip(unsure, again_read):
                firsts[i] = read[i][0]
                read[i] = (logits, len(ctx))
                pieces[i] = rows[i][3]
        probs = [self._probs(logits, n) for (logits, _), n in zip(read, ns)]
        flipped = {}
        if self.reverse_below > 0:
            low = [i for i, pr in enumerate(probs) if max(pr) < self.reverse_below]
            if low:
                twice = [whole or i in firsts for i in low]
                rev = [self.layout.question(rendered[i][2], rendered[i][3][::-1], again if t else None) for i, t in zip(low, twice)]
                for i, piece in zip(low, rev):
                    if len(ctx) + len(piece) > self.limit:
                        raise Unsupported(f"maximum context length: a row of {len(ctx) + len(piece)} tokens exceeds the declared limit of {self.limit}")
                for i, (logits, _) in zip(low, self._read(ctx, rev, [ns[i] for i in low], reuse=True)):
                    back = self._probs(logits, ns[i])[::-1]                   # reversed positions back to the caller's order
                    flipped[i] = logits
                    probs[i] = [(a + b) / 2 for a, b in zip(probs[i], back)]
        answers, raw = {}, {}
        for i, ((key, kind, _, _, keys), (logits, p)) in enumerate(zip(rows, read)):
            raw[key] = {"label_logits": [round(x, 4) for x in logits.tolist()], "prompt_tokens": len(ctx) + len(pieces[i]), "cached_prefix_tokens": p,
                        "read_twice": whole or i in firsts}
            if i in firsts:
                raw[key]["first_label_logits"] = [round(x, 4) for x in firsts[i].tolist()]
            if i in flipped:
                raw[key]["reversed_label_logits"] = [round(x, 4) for x in flipped[i].tolist()]
            probs_i = probs[i]
            if kind == "noul":
                answers[key] = {"type": "noul", "noul": probs_i[1]}
            else:
                answers[key] = {"type": "choice", "choice": keys[max(range(len(keys)), key=probs_i.__getitem__)], "probabilities": dict(zip(keys, probs_i))}
        return {"model": self.model_id, "answers": answers, "usage": {"input_tokens": sum(v["prompt_tokens"] for v in raw.values())}}, raw