minimind/course/labs/compare_pretrain_sft.py

94 lines
3.7 KiB
Python

import argparse
import json
import os
import sys
from pathlib import Path
import torch
from transformers import AutoTokenizer
ROOT = Path(__file__).resolve().parents[2]
sys.path.insert(0, str(ROOT))
from dataset.lm_dataset import PretrainDataset, SFTDataset, post_processing_chat, pre_processing_chat
def decode_label(tokenizer, token_id):
if int(token_id) == -100:
return "<ignored>"
return tokenizer.decode([int(token_id)], skip_special_tokens=False).replace("\n", "\\n")
def print_table(title, tokenizer, input_ids, labels, rows):
print(f"[{title}]")
print(f"input_ids.shape={tuple(input_ids.shape)}")
print(f"labels.shape={tuple(labels.shape)}")
print(f"non_ignored_labels={(labels != -100).sum().item()}")
print("idx | input_id | token | label | label_token")
print("-" * 72)
for i in range(min(rows, len(input_ids))):
tid = int(input_ids[i])
label = int(labels[i])
token = tokenizer.decode([tid], skip_special_tokens=False).replace("\n", "\\n")
print(f"{i:03d} | {tid:8d} | {token!r:16s} | {label:6d} | {decode_label(tokenizer, label)!r}")
print()
def make_deterministic_sft_sample(tokenizer, data_path, index, max_length):
ds = SFTDataset(data_path, tokenizer, max_length=max_length)
with open(data_path, "r", encoding="utf-8") as f:
raw_sample = json.loads(f.readlines()[index])
conversations = pre_processing_chat(raw_sample["conversations"], add_system_ratio=0.0)
prompt = ds.create_chat_prompt(conversations)
prompt = post_processing_chat(prompt, empty_think_ratio=1.0)
input_ids = tokenizer(prompt).input_ids[:max_length]
input_ids += [tokenizer.pad_token_id] * (max_length - len(input_ids))
labels = ds.generate_labels(input_ids)
return prompt, torch.tensor(input_ids, dtype=torch.long), torch.tensor(labels, dtype=torch.long)
def main():
parser = argparse.ArgumentParser(description="Compare MiniMind pretrain and SFT dataset targets.")
parser.add_argument("--tokenizer_path", default=str(ROOT / "model"))
parser.add_argument("--pretrain_path", default=str(ROOT / "course/labs/tiny_pretrain.jsonl"))
parser.add_argument("--sft_path", default=str(ROOT / "course/labs/tiny_sft.jsonl"))
parser.add_argument("--pretrain_index", type=int, default=0)
parser.add_argument("--sft_index", type=int, default=0)
parser.add_argument("--max_length", type=int, default=80)
parser.add_argument("--show_rows", type=int, default=70)
args = parser.parse_args()
tokenizer = AutoTokenizer.from_pretrained(args.tokenizer_path)
pretrain_ds = PretrainDataset(args.pretrain_path, tokenizer, max_length=args.max_length)
pretrain_input_ids, pretrain_labels = pretrain_ds[args.pretrain_index]
sft_prompt, sft_input_ids, sft_labels = make_deterministic_sft_sample(
tokenizer, args.sft_path, args.sft_index, args.max_length
)
with open(args.pretrain_path, "r", encoding="utf-8") as f:
pretrain_raw = json.loads(f.readlines()[args.pretrain_index])
print("[Pretrain raw text]")
print(pretrain_raw["text"])
print()
print_table("Pretrain input_ids / labels", tokenizer, pretrain_input_ids, pretrain_labels, args.show_rows)
print("[SFT prompt]")
print(sft_prompt)
print()
print_table("SFT input_ids / labels", tokenizer, sft_input_ids, sft_labels, args.show_rows)
print("[Comparison]")
print("Pretrain: labels mostly copy input_ids, except padding is -100.")
print("SFT: labels are -100 for user/system/padding, and token ids only for assistant response spans.")
if __name__ == "__main__":
os.environ.setdefault("TOKENIZERS_PARALLELISM", "false")
torch.set_printoptions(linewidth=160)
main()