338 lines
10 KiB
Python
338 lines
10 KiB
Python
"""Mask building for preprocessing pipeline.
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:class:`SectionRenderer` converts section specs into token ids and loss
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masks (template / text / value extraction). :class:`SingleOutputMaskBuilder`
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handles single-output (SFT / pretrain), :class:`MultiOutputMaskBuilder`
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handles multi-output (DPO / GRPO), and :class:`SectionedMaskBuilder`
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orchestrates both modes as a façade.
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"""
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from abc import ABC, abstractmethod
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from typing import Optional
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from astrai.factory import BaseFactory
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def _extract_domain(item: dict, domain_key: Optional[str]) -> str:
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if not domain_key:
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return "__default__"
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val = item.get(domain_key, "__default__")
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return val if isinstance(val, str) else "__default__"
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def _resolve_action(action: str, role: str, config) -> str:
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if action == "$role":
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return config.mask.get(role, config.mask_default)
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return action
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class SectionRenderer:
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"""Render section specs into ``(ids, loss_mask)`` tuples."""
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def process_sections(
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self,
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item: dict,
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sections: list,
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config,
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tokenizer,
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*,
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is_top_level: bool = False,
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):
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all_ids: list[int] = []
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loss_mask: list[int] = []
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has_template = any(s.get("template") for s in sections)
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is_text_config = not has_template and all(
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s["action"] == "train" for s in sections
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)
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if is_top_level and has_template and tokenizer.bos_token_id is not None:
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all_ids.append(tokenizer.bos_token_id)
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loss_mask.append(0)
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first_section = True
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for sec in sections:
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field = sec["field"]
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action = sec["action"]
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use_template = sec.get("template", False)
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add_special = sec.get(
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"add_special_tokens", not use_template and first_section
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)
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if use_template:
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success = self._append_template(
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item, field, action, tokenizer, config, all_ids, loss_mask
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)
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if not success:
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continue
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else:
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success = self._append_text(
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item,
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field,
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action,
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tokenizer,
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add_special,
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is_text_config,
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config,
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all_ids,
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loss_mask,
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)
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if not success:
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continue
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first_section = False
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max_len = config.preprocessing.max_seq_len
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all_ids = all_ids[:max_len]
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loss_mask = loss_mask[: len(all_ids)]
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if not all_ids:
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return None, None
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if is_top_level and has_template and len(all_ids) <= 1:
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return None, None
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return all_ids, loss_mask
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def process_list_field(self, item: dict, sections: list, config, tokenizer):
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"""Tokenize a list-valued field, preserving per-element boundaries.
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Returns ``(list_of_id_lists, list_of_mask_lists)`` where each
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inner list corresponds to one element of the source list. This
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is critical for GRPO where each response must stay a separate
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sequence so the strategy can form a ``[G, R]`` tensor.
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"""
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per_item_ids: list[list[int]] = []
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per_item_masks: list[list[int]] = []
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for sec in sections:
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field = sec["field"]
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action = sec["action"]
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use_template = sec.get("template", False)
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values = item.get(field)
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if not isinstance(values, list):
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continue
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for val in values:
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ids: list[int] = []
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mask: list[int] = []
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if use_template:
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if isinstance(val, list):
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wrapper = {field: val}
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self._append_template(
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wrapper, field, action, tokenizer, config, ids, mask
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)
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else:
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wrapper = {field: str(val)}
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self._append_text(
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wrapper,
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field,
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action,
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tokenizer,
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False,
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False,
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config,
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ids,
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mask,
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)
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if ids:
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max_len = config.preprocessing.max_seq_len
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ids = ids[:max_len]
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mask = mask[: len(ids)]
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per_item_ids.append(ids)
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per_item_masks.append(mask)
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if not per_item_ids:
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return None, None
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return per_item_ids, per_item_masks
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@staticmethod
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def is_value_section(sections: list) -> bool:
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return len(sections) == 1 and sections[0].get("action") == "value"
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@staticmethod
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def extract_raw_value(item: dict, sections: list):
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sec = sections[0]
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field = sec["field"]
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raw = item.get(field)
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if raw is None:
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return None
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if isinstance(raw, list):
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return [float(v) for v in raw]
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return [float(raw)]
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def _append_template(
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self, item, field, action, tokenizer, config, all_ids, loss_mask
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):
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messages = item.get(field)
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if not isinstance(messages, list) or not messages:
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return False
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for msg in messages:
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role = msg.get("role", "")
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act = _resolve_action(action, role, config)
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rendered = tokenizer.apply_chat_template(
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[msg], tokenize=False, add_generation_prompt=False
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)
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ids = tokenizer.encode(rendered, add_special_tokens=False)
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all_ids.extend(ids)
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val = 1 if act == "train" else 0
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loss_mask.extend([val] * len(ids))
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return True
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def _append_text(
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self,
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item,
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field,
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action,
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tokenizer,
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add_special,
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is_text_config,
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config,
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all_ids,
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loss_mask,
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):
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text = str(item.get(field, ""))
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if not text.strip():
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return False
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if is_text_config:
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pp = config.preprocessing
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if pp.min_chars > 0 and len(text) < pp.min_chars:
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return False
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if len(text) > pp.max_chars:
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return False
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ids = tokenizer.encode(text, add_special_tokens=add_special)
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all_ids.extend(ids)
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val = 1 if action == "train" else 0
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loss_mask.extend([val] * len(ids))
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return True
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class BaseMaskBuilder(ABC):
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"""Convert a JSONL item into token ids and optional loss_mask."""
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@abstractmethod
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def build(self, item: dict, config, tokenizer) -> Optional[dict]: ...
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class MaskBuilderFactory(BaseFactory["BaseMaskBuilder"]):
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pass
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@MaskBuilderFactory.register("single")
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class SingleOutputMaskBuilder(BaseMaskBuilder):
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"""Build a single output sequence with optional loss mask.
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Expects ``config.input.sections`` (list of section specs).
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"""
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def __init__(self, renderer: Optional[SectionRenderer] = None):
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self.renderer = renderer or SectionRenderer()
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def build(self, item: dict, config, tokenizer) -> Optional[dict]:
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sections = config.input.sections
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if not sections:
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return None
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ids, mask = self.renderer.process_sections(
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item, sections, config, tokenizer, is_top_level=True
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)
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if ids is None:
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return None
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result: dict = {
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"sequence": ids,
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"domain": _extract_domain(item, config.output.domain_key),
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}
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if not all(m == 1 for m in mask):
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result["loss_mask"] = mask
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return result
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@MaskBuilderFactory.register("multi")
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class MultiOutputMaskBuilder(BaseMaskBuilder):
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"""Build multiple output sequences (DPO / GRPO).
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Expects ``config.input.sources`` (dict of output_key → spec).
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"""
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def __init__(self, renderer: Optional[SectionRenderer] = None):
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self.renderer = renderer or SectionRenderer()
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def build(self, item: dict, config, tokenizer) -> Optional[dict]:
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sources_spec = getattr(config.input, "sources", None)
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if not sources_spec:
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return None
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result: dict = {}
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any_output = False
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for output_key, spec in sources_spec.items():
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sections = spec.get("sections", [])
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if not sections:
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continue
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if self.renderer.is_value_section(sections):
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ids = self.renderer.extract_raw_value(item, sections)
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if ids is None:
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continue
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result[output_key] = ids
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any_output = True
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continue
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list_field = spec.get("list_field", False)
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mask_key = spec.get("mask_key", f"{output_key}_mask")
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if list_field:
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ids, mask = self.renderer.process_list_field(
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item, sections, config, tokenizer
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)
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if ids is None:
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continue
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# ids is List[List[int]] — preserve per-response structure
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result[output_key] = ids
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if mask is not None:
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result[mask_key] = mask
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any_output = True
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continue
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ids, mask = self.renderer.process_sections(
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item, sections, config, tokenizer, is_top_level=True
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)
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if ids is None:
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continue
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result[output_key] = ids
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if not all(m == 1 for m in mask):
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result[mask_key] = mask
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elif "mask_key" in spec:
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result[mask_key] = mask
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any_output = True
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if not any_output:
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return None
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result["domain"] = _extract_domain(item, config.output.domain_key)
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return result
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@MaskBuilderFactory.register("sectioned")
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class SectionedMaskBuilder(BaseMaskBuilder):
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"""Façade that dispatches to SingleOutputMaskBuilder or MultiOutputMaskBuilder.
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Preserves backward compatibility for existing configs and code that rely
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on the ``"sectioned"`` factory name.
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"""
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def __init__(self):
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self._single = SingleOutputMaskBuilder()
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self._multi = MultiOutputMaskBuilder()
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def build(self, item: dict, config, tokenizer) -> Optional[dict]:
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sources_spec = getattr(config.input, "sources", None)
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if sources_spec:
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return self._multi.build(item, config, tokenizer)
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return self._single.build(item, config, tokenizer)
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