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chore: import upstream snapshot with attribution
2026-07-13 13:22:06 +08:00

57 lines
2.2 KiB
Python

import torch
from transformers import PreTrainedModel, PreTrainedTokenizerBase
DEFAULT_SYSTEM_PROMPT = (
"You are an expert prompt writer for AI image generation. "
"Given a brief description, expand it into a detailed, vivid prompt suitable for generating high-quality images. "
"Only output the expanded prompt, nothing else."
)
class TextLLMPipeline:
"""A wrapper for a causal language model + tokenizer for text generation."""
def __init__(self, model: PreTrainedModel, tokenizer: PreTrainedTokenizerBase):
self._model = model
self._tokenizer = tokenizer
def run(
self,
prompt: str,
system_prompt: str = DEFAULT_SYSTEM_PROMPT,
max_new_tokens: int = 300,
device: torch.device = torch.device("cpu"),
dtype: torch.dtype = torch.float16,
) -> str:
# Build messages for chat template if supported, otherwise use raw prompt.
if hasattr(self._tokenizer, "apply_chat_template") and self._tokenizer.chat_template is not None:
messages = []
if system_prompt:
messages.append({"role": "system", "content": system_prompt})
messages.append({"role": "user", "content": prompt})
formatted_prompt: str = self._tokenizer.apply_chat_template(
messages, tokenize=False, add_generation_prompt=True
)
else:
# Fallback for models without chat template
if system_prompt:
formatted_prompt = f"{system_prompt}\n\nUser: {prompt}\nAssistant:"
else:
formatted_prompt = prompt
inputs = self._tokenizer(formatted_prompt, return_tensors="pt").to(device=device)
output = self._model.generate(
**inputs,
max_new_tokens=max_new_tokens,
do_sample=True,
temperature=0.7,
top_p=0.9,
)
# Decode only the newly generated tokens (exclude the input prompt tokens).
input_length = inputs["input_ids"].shape[1]
generated_tokens = output[0][input_length:]
response = self._tokenizer.decode(generated_tokens, skip_special_tokens=True).strip()
return response