sprout-instruct / tokenizer.py
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Release instruction-tuned Sprout with standalone inference
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import json
import os
import sys
from collections import Counter, defaultdict
from multiprocessing import Pool
import numpy as np
import regex
VOCAB_SIZE = 4096
SPECIALS = ["<|endoftext|>", "<|user|>", "<|assistant|>", "<|end|>"]
SAMPLE_MB = 30
STRIDE = 64
OUT = "data"
# GPT-4's pre-split pattern: text is cut into chunks first, so no merge can
# span a word boundary.
PAT = regex.compile(
r"""'(?i:[sdmt]|ll|ve|re)|[^\r\n\p{L}\p{N}]?+\p{L}+|\p{N}{1,3}"""
r"""| ?[^\s\p{L}\p{N}]++[\r\n]*|\s*[\r\n]|\s+(?!\S)|\s+"""
)
SPECIAL_PAT = regex.compile("(" + "|".join(regex.escape(s) for s in SPECIALS) + ")")
def merge(ids, pair, new):
"""Replace every occurrence of pair in ids with the single token new."""
out, i = [], 0
while i < len(ids):
if i + 1 < len(ids) and (ids[i], ids[i + 1]) == pair:
out.append(new)
i += 2
else:
out.append(ids[i])
i += 1
return out
def train(text, n_merges):
"""Learn n_merges pairs, in the order learned."""
# Chunks are deduplicated and weighted by count: identical chunks always
# merge identically, and 30MB holds only ~50k distinct ones.
freq = Counter(PAT.findall(text))
words = [list(w.encode("utf-8")) for w in freq]
reps = list(freq.values())
count = defaultdict(int) # pair -> how often it occurs
where = defaultdict(set) # pair -> which words contain it
for i, w in enumerate(words):
for p, k in Counter(zip(w, w[1:])).items():
count[p] += k * reps[i]
where[p].add(i)
merges = []
for new in range(256, 256 + n_merges):
best = max(count, key=lambda p: (count[p], -p[0], -p[1])) # ties: smallest pair
merges.append(best)
# Only the words containing best change: drop their pairs, merge, put
# the new pairs back.
for i in where.pop(best):
w, r = words[i], reps[i]
for p, k in Counter(zip(w, w[1:])).items():
count[p] -= k * r
if count[p] == 0:
del count[p]
words[i] = w = merge(w, best, new)
for p, k in Counter(zip(w, w[1:])).items():
count[p] += k * r
where[p].add(i)
return merges
class Tokenizer:
def __init__(self, merges):
self.ranks = {p: 256 + i for i, p in enumerate(merges)}
self.vocab = {i: bytes([i]) for i in range(256)}
for i, (a, b) in enumerate(merges):
self.vocab[256 + i] = self.vocab[a] + self.vocab[b]
base = 256 + len(merges)
self.special = {s: base + i for i, s in enumerate(SPECIALS)}
for s, i in self.special.items():
self.vocab[i] = s.encode("utf-8")
self.cache = {} # chunk -> ids, looked up ~400M times over the corpus
def encode_chunk(self, chunk):
"""Apply the merges to one chunk, earliest-learned pair first."""
ids = self.cache.get(chunk)
if ids is not None:
return ids
ids = list(chunk.encode("utf-8"))
while len(ids) > 1:
pair = min(zip(ids, ids[1:]), key=lambda p: self.ranks.get(p, 1 << 30))
if pair not in self.ranks:
break
ids = merge(ids, pair, self.ranks[pair])
self.cache[chunk] = ids
return ids
def encode(self, text):
# Specials are split out first, so BPE never sees them and cannot
# shred one into pieces.
ids = []
for part in SPECIAL_PAT.split(text):
if part in self.special:
ids.append(self.special[part])
else:
ids += [i for c in PAT.findall(part) for i in self.encode_chunk(c)]
return ids
def decode(self, ids):
return b"".join(self.vocab[i] for i in ids).decode("utf-8", errors="replace")
def save(merges, path):
with open(path, "w") as f:
f.writelines(f"{a} {b}\n" for a, b in merges)
def load(path=f"{OUT}/tokenizer.model"):
with open(path) as f:
return Tokenizer([tuple(int(x) for x in line.split()) for line in f])
def sample(path, mb, stride):
"""Every stride-th story, up to mb megabytes, so the sample spans the corpus."""
parts, n = [], 0
with open(path, encoding="utf-8") as f:
for i, line in enumerate(f):
if i % stride:
continue
parts.append(json.loads(line)["text"])
n += len(parts[-1])
if n > mb * 1e6:
break
return "\n".join(parts)
def batches(path, n=2000):
"""Stories from a .jsonl file, n at a time."""
batch = []
with open(path, encoding="utf-8") as f:
for line in f:
batch.append(json.loads(line)["text"])
if len(batch) == n:
yield batch
batch = []
if batch:
yield batch
enc = None # one Tokenizer per worker process
def init_worker(merges):
global enc
enc = Tokenizer(merges)
def encode_batch(batch):
eot = enc.special["<|endoftext|>"]
ids, nbytes = [], 0
for s in batch:
story = enc.encode(s)
assert enc.decode(story) == s, s[:80] # lossless only if every char lands in a chunk
ids += story + [eot]
nbytes += len(s.encode("utf-8"))
return np.array(ids, dtype=np.uint16), nbytes, len(ids) - len(batch)
def tokenize(name, merges, out):
"""Write <out>/<name>.bin, return its byte and token counts."""
ntok = nbytes = 0
with Pool(initializer=init_worker, initargs=(merges,)) as pool:
with open(f"{out}/{name}.bin", "wb") as f:
for arr, nb, nt in pool.imap(encode_batch, batches(f"{OUT}/{name}.jsonl")):
f.write(arr.tobytes())
nbytes += nb
ntok += nt
return nbytes, ntok
def main():
# Any other vocab size goes in its own directory, next to the same jsonl.
vocab = int(sys.argv[1]) if len(sys.argv) > 1 else VOCAB_SIZE
out = OUT if vocab == VOCAB_SIZE else f"{OUT}/vocab{vocab}"
os.makedirs(out, exist_ok=True)
n_merges = vocab - 256 - len(SPECIALS)
text = sample(f"{OUT}/train.jsonl", SAMPLE_MB, STRIDE)
print(f"training on {len(text) / 1e6:.1f}MB, {len(set(PAT.findall(text))):,} chunks")
merges = train(text, n_merges)
save(merges, f"{out}/tokenizer.model")
tok = load(f"{out}/tokenizer.model")
assert len(tok.vocab) == vocab, len(tok.vocab)
word = tok.encode("story")
for s in SPECIALS:
assert tok.encode(f"story{s}story") == word + [tok.special[s]] + word, s
step = n_merges // 18
print("vocab:", ", ".join(repr(tok.vocab[i].decode("utf-8", "replace"))
for i in range(256, 256 + n_merges, step)))
for name in ("val", "train"):
nbytes, ntok = tokenize(name, merges, out)
print(f"{name}: {ntok:,} tokens, {nbytes / ntok:.3f} bytes/token")
ids = np.memmap(f"{out}/train.bin", dtype=np.uint16, mode="r")[:220]
print("\n" + tok.decode(ids.tolist()))
if __name__ == "__main__":
main()