# Copyright 2025 OpenAccess AI Collective and the LlamaFactory team. # # This code is inspired by the OpenAccess AI Collective's axolotl library. # https://github.com/OpenAccess-AI-Collective/axolotl/blob/main/src/axolotl/monkeypatch/utils.py # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. import copy import inspect from dataclasses import dataclass from typing import TYPE_CHECKING, Any, Literal, Optional import numpy as np import torch import torch.nn.functional as F from peft import PeftModel from transformers import DataCollatorForSeq2Seq from ..extras.constants import AUDIO_PLACEHOLDER, IGNORE_INDEX, IMAGE_PLACEHOLDER, MROPE_MODELS from ..extras.packages import is_pillow_available if is_pillow_available(): from PIL import Image if TYPE_CHECKING: from transformers import ProcessorMixin from .template import Template def _slice_mm_inputs_for_sample( mm_inputs: dict[str, Any], batch_imglens: list[int], batch_vidlens: list[int], batch_idx: int, images_per_subseq: Optional[list[int]] = None, videos_per_subseq: Optional[list[int]] = None, subseq_idx: Optional[int] = None, ) -> dict[str, Any]: r"""Slice mm_inputs for one batch sample, optionally for a single sub-sequence when packing. image_grid_thw / video_grid_thw have shape [num_items, 3]. Indices for sample batch_idx are batch_imglens[batch_idx] images and batch_vidlens[batch_idx] videos. When subseq_idx is given, further restrict to that sub-seq's counts via packed_*_counts. has_dummy_image=True means only batch[0] will be concated with fake image and no multimodal data. """ image_start_idx = sum(batch_imglens[:batch_idx]) image_end_idx = sum(batch_imglens[: batch_idx + 1]) video_start_idx = sum(batch_vidlens[:batch_idx]) video_end_idx = sum(batch_vidlens[: batch_idx + 1]) if subseq_idx is not None and images_per_subseq is not None: image_start_idx += sum(images_per_subseq[:subseq_idx]) image_end_idx = image_start_idx + images_per_subseq[subseq_idx] if subseq_idx is not None and videos_per_subseq is not None: video_start_idx += sum(videos_per_subseq[:subseq_idx]) video_end_idx = video_start_idx + videos_per_subseq[subseq_idx] sliced_mm_inputs: dict[str, Any] = {} key_to_slice_meta = { "image_grid_thw": (image_start_idx, image_end_idx, True), "video_grid_thw": (video_start_idx, video_end_idx, True), "second_per_grid_ts": (video_start_idx, video_end_idx, False), # qwen2.5vl "video_second_per_grid": (video_start_idx, video_end_idx, False), # qwen omni } for key, (start_idx, end_idx, assign_none_when_empty) in key_to_slice_meta.items(): if key not in mm_inputs: continue mm_value = mm_inputs[key] if mm_value is not None and end_idx > start_idx: sliced_mm_inputs[key] = mm_value[start_idx:end_idx] elif assign_none_when_empty: sliced_mm_inputs[key] = None return sliced_mm_inputs def prepare_4d_attention_mask(attention_mask_with_indices: "torch.Tensor", dtype: "torch.dtype") -> "torch.Tensor": r"""Expand 2d attention mask to 4d attention mask. Expand the attention mask with indices from (batch_size, seq_len) to (batch_size, 1, seq_len, seq_len), handle packed sequences and transforms the mask to lower triangular form to prevent future peeking. e.g. ```python # input [[1, 1, 2, 2, 2, 0]] # output [ [ [ [o, x, x, x, x, x], [o, o, x, x, x, x], [x, x, o, x, x, x], [x, x, o, o, x, x], [x, x, o, o, o, x], [x, x, x, x, x, x], ] ] ] ``` where `o` equals to `0.0`, `x` equals to `min_dtype`. """ _, seq_len = attention_mask_with_indices.size() min_dtype = torch.finfo(dtype).min zero_tensor = torch.tensor(0, dtype=dtype) # Create a non-padding mask. non_padding_mask = (attention_mask_with_indices != 0).unsqueeze(1).unsqueeze(2) # Create indices for comparison. indices = attention_mask_with_indices.unsqueeze(1).unsqueeze(2) # [bsz, 1, 1, seq_len] indices_t = attention_mask_with_indices.unsqueeze(1).unsqueeze(3) # [bsz, 1, seq_len, 1] # Create a lower triangular mask. tril_mask = torch.tril(torch.ones((seq_len, seq_len), dtype=torch.bool)) attention_mask_4d = (indices == indices_t) & non_padding_mask & tril_mask # Invert the attention mask. attention_mask_4d = torch.where(attention_mask_4d, zero_tensor, min_dtype) return attention_mask_4d @dataclass class MultiModalDataCollatorForSeq2Seq(DataCollatorForSeq2Seq): r"""Data collator that supports VLMs. Features should contain input_ids, attention_mask, labels, and optionally contain images, videos and audios. """ template: Optional["Template"] = None processor: Optional["ProcessorMixin"] = None def __post_init__(self): if self.template is None: raise ValueError("Template is required for MultiModalDataCollator.") if isinstance(self.model, PeftModel): self.model = self.model.base_model.model if self.model is not None and hasattr(self.model, "get_rope_index"): # for qwen2vl mrope self.get_rope_func = self.model.get_rope_index # transformers < 4.52.0 or qwen2.5 omni elif self.model is not None and hasattr(self.model, "model") and hasattr(self.model.model, "get_rope_index"): self.get_rope_func = self.model.model.get_rope_index # transformers >= 4.52.0 else: self.get_rope_func = None def _compute_rope_position_ids( self, features: dict[str, "torch.Tensor"], mm_inputs: dict[str, Any] ) -> None: r"""Compute position_ids and rope_deltas via get_rope_func for VLMs.""" rope_index_kwargs = { "input_ids": features["input_ids"], "image_grid_thw": mm_inputs.get("image_grid_thw"), "video_grid_thw": mm_inputs.get("video_grid_thw"), "attention_mask": (features["attention_mask"] >= 1).float(), } if features["attention_mask"].sum() == 0: features["position_ids"] = torch.zeros((3, *features["input_ids"].shape)) features["rope_deltas"] = torch.zeros(features["input_ids"].shape[0]) return if "mm_token_type_ids" in inspect.signature(self.get_rope_func).parameters: image_token_id = getattr(self.model.config, "image_token_id", None) video_token_id = getattr(self.model.config, "video_token_id", None) if image_token_id is not None or video_token_id is not None: mm_token_type_ids = torch.zeros_like(features["input_ids"]) if image_token_id is not None: mm_token_type_ids[features["input_ids"] == image_token_id] = 1 if video_token_id is not None: mm_token_type_ids[features["input_ids"] == video_token_id] = 2 rope_index_kwargs["mm_token_type_ids"] = mm_token_type_ids if "second_per_grid_ts" in mm_inputs: # for qwen2vl rope_index_kwargs["second_per_grid_ts"] = mm_inputs.get("second_per_grid_ts") elif "video_second_per_grid" in mm_inputs: # for qwen2.5 omni rope_index_kwargs["second_per_grids"] = mm_inputs.get("video_second_per_grid") if getattr(self.model.config, "model_type", None) in ["qwen2_5_omni_thinker", "qwen3_omni_moe_thinker"]: rope_index_kwargs["use_audio_in_video"] = getattr(self.processor, "use_audio_in_video", False) feature_attention_mask = mm_inputs.get("feature_attention_mask", None) if feature_attention_mask is not None: # FIXME: need to get video image lengths audio_feature_lengths = torch.sum(feature_attention_mask, dim=1) rope_index_kwargs["audio_seqlens"] = audio_feature_lengths # prepare for input features["position_ids"], rope_deltas = self.get_rope_func(**rope_index_kwargs) features["rope_deltas"] = rope_deltas - (1 - rope_index_kwargs["attention_mask"]).sum( dim=-1 ).unsqueeze(-1) else: # for qwen vl features["position_ids"], features["rope_deltas"] = self.get_rope_func(**rope_index_kwargs) def _compute_rope_position_ids_with_packing( self, features: dict[str, "torch.Tensor"], mm_inputs: dict[str, Any], packing_params_list: list[dict[str, Any] | None], batch_imglens: list[int], batch_vidlens: list[int], batch_audlens: list[int], has_dummy_image: bool, ) -> None: r"""Compute position_ids and rope_deltas per sample (or per sub-sequence when packed), then merge and validate.""" bsz = features["input_ids"].size(0) seq_len = features["input_ids"].size(1) all_position_ids: list[torch.Tensor] = [] all_rope_deltas: list[torch.Tensor] = [] if has_dummy_image: # for [0, seq_len] = [0, unpadded_length + right_padding_length + fake_input_ids_len + collator_padding_length] # FIXME: maybe right_padding_length is large, with improper max_cutoff_len unpadded_length = int(features["attention_mask"][0].bool().sum().item()) right_padding_length = int((packing_params_list[0] or {}).get("right_padding_length") or 0) fake_input_padding_length = max(0, seq_len - unpadded_length - right_padding_length) dummy_image_right_padding_mrope = torch.zeros((3, bsz, fake_input_padding_length)) dummy_image_right_padding_attention_mask = torch.zeros((bsz, fake_input_padding_length)) assert self.tokenizer.padding_side == "right", "padding_side should be right when fake image is injected" dummy_mm_inputs = copy.deepcopy(mm_inputs) for sample_idx in range(bsz): sample_packing = (packing_params_list[sample_idx] or {}) if sample_idx < len(packing_params_list) else {} sequence_boundaries = sample_packing.get("sequence_boundaries") num_sub_seqs = (len(sequence_boundaries) - 1) if sequence_boundaries and len(sequence_boundaries) > 1 else 1 image_subseq_ids = sample_packing.get("image_subseq_ids") or [] video_subseq_ids = sample_packing.get("video_subseq_ids") or [] images_per_subseq = ( [image_subseq_ids.count(i) for i in range(num_sub_seqs)] if image_subseq_ids and num_sub_seqs > 1 else None ) videos_per_subseq = ( [video_subseq_ids.count(i) for i in range(num_sub_seqs)] if video_subseq_ids and num_sub_seqs > 1 else None ) if has_dummy_image: mm_inputs = {} if num_sub_seqs <= 1: sample_features = { "input_ids": features["input_ids"], "attention_mask": features["attention_mask"][sample_idx : sample_idx + 1], } mm_inputs_for_sample = _slice_mm_inputs_for_sample( mm_inputs, batch_imglens, batch_vidlens, sample_idx=sample_idx ) self._compute_rope_position_ids(sample_features, mm_inputs_for_sample) all_position_ids.append(sample_features["position_ids"]) all_rope_deltas.append(sample_features["rope_deltas"]) else: # when we do packing, don't need rope_deltas when training. sample_position_ids: list[torch.Tensor] = [] for subseq_idx in range(num_sub_seqs): subseq_start = sequence_boundaries[subseq_idx] subseq_end = sequence_boundaries[subseq_idx + 1] subseq_features = { "input_ids": features["input_ids"][sample_idx : sample_idx + 1, subseq_start:subseq_end], "attention_mask": features["attention_mask"][sample_idx : sample_idx + 1, subseq_start:subseq_end], } mm_inputs_for_subseq = _slice_mm_inputs_for_sample( mm_inputs, batch_imglens, batch_vidlens, sample_idx, images_per_subseq, videos_per_subseq, subseq_idx ) self._compute_rope_position_ids(subseq_features, mm_inputs_for_subseq) sample_position_ids.append(subseq_features["position_ids"]) all_position_ids.append(torch.cat(sample_position_ids, dim=-1)) batch_dim_for_position_ids = 1 if all_position_ids[0].dim() == 3 else 0 features["position_ids"] = torch.cat(all_position_ids, dim=batch_dim_for_position_ids) if has_dummy_image: mm_inputs = dummy_mm_inputs expected_position_ids_shape = (bsz, seq_len) if all_position_ids[0].dim() == 2 else ( all_position_ids[0].size(0), bsz, seq_len, ) # Check if position_ids shape matches expected shape. # for further usage, we should padding to the right when some padding token on the right. if has_dummy_image: features["position_ids"] = torch.cat([features["position_ids"], dummy_image_right_padding_mrope], dim=-1) features["attention_mask"] = torch.cat([features["attention_mask"], dummy_image_right_padding_attention_mask], dim=-1) if features["position_ids"].shape != expected_position_ids_shape: raise ValueError( "Merged position_ids shape mismatch: " f"got {features['position_ids'].shape}, expected {expected_position_ids_shape}." ) def __call__(self, features: list[dict[str, Any]]) -> dict[str, "torch.Tensor"]: batch_images, batch_videos, batch_audios = [], [], [] batch_imglens, batch_vidlens, batch_audlens, batch_input_ids = [], [], [], [] packing_params_list: list[dict[str, Any] | None] = [] for feature in features: images = feature.pop("images", None) or [] videos = feature.pop("videos", None) or [] audios = feature.pop("audios", None) or [] batch_images.extend(images) batch_videos.extend(videos) batch_audios.extend(audios) batch_imglens.append(len(images)) batch_vidlens.append(len(videos)) batch_audlens.append(len(audios)) batch_input_ids.append(feature["input_ids"]) packing_params_list.append(feature.pop("packing_params", None)) fake_input_ids = [] has_dummy_image = False if ( self.template.mm_plugin.image_token is not None and sum(batch_imglens) == 0 and sum(batch_vidlens) == 0 ): # avoid process hanging in zero3/fsdp case fake_messages = [{"role": "user", "content": IMAGE_PLACEHOLDER}] fake_images = [Image.new("RGB", (64, 64), (255, 255, 255))] fake_messages = self.template.mm_plugin.process_messages( fake_messages, fake_images, [], [], self.processor ) _fake_input_ids = self.tokenizer.encode(fake_messages[0]["content"], add_special_tokens=False) _fake_input_ids, _ = self.template.mm_plugin.process_token_ids( _fake_input_ids, None, fake_images, [], [], self.tokenizer, self.processor ) fake_input_ids.extend(_fake_input_ids) batch_images = fake_images batch_imglens[0] = 1 has_dummy_image = True if ( self.template.mm_plugin.audio_token is not None and sum(batch_audlens) == 0 ): # avoid process hanging in zero3/fsdp case fake_messages = [{"role": "user", "content": AUDIO_PLACEHOLDER}] fake_audios = [np.zeros(1600)] fake_messages = self.template.mm_plugin.process_messages( fake_messages, [], [], fake_audios, self.processor ) _fake_input_ids = self.tokenizer.encode(fake_messages[0]["content"], add_special_tokens=False) _fake_input_ids, _ = self.template.mm_plugin.process_token_ids( _fake_input_ids, None, [], [], fake_audios, self.tokenizer, self.processor ) fake_input_ids.extend(_fake_input_ids) batch_audios = fake_audios batch_audlens[0] = 1 if len(fake_input_ids) != 0: if self.tokenizer.padding_side == "right": features[0]["input_ids"] = features[0]["input_ids"] + fake_input_ids features[0]["attention_mask"] = features[0]["attention_mask"] + [0] * len(fake_input_ids) features[0]["labels"] = features[0]["labels"] + [IGNORE_INDEX] * len(fake_input_ids) else: features[0]["input_ids"] = fake_input_ids + features[0]["input_ids"] features[0]["attention_mask"] = [0] * len(fake_input_ids) + features[0]["attention_mask"] features[0]["labels"] = [IGNORE_INDEX] * len(fake_input_ids) + features[0]["labels"] batch_input_ids[0] = features[0]["input_ids"] mm_inputs = self.template.mm_plugin.get_mm_inputs( batch_images, batch_videos, batch_audios, batch_imglens, batch_vidlens, batch_audlens, batch_input_ids, self.processor, ) if "token_type_ids" in mm_inputs: token_type_ids = mm_inputs.pop("token_type_ids") for i, feature in enumerate(features): feature["token_type_ids"] = token_type_ids[i] if "mm_token_type_ids" in mm_inputs: # need tensor-like for gemma4 mm_token_type_ids = mm_inputs.pop("mm_token_type_ids") max_len = max(len(ids) for ids in mm_token_type_ids) padded = [] for ids in mm_token_type_ids: pad_len = max_len - len(ids) if self.tokenizer.padding_side == "right": padded.append(ids + [0] * pad_len) else: padded.append([0] * pad_len + ids) mm_inputs["mm_token_type_ids"] = torch.tensor(padded, dtype=torch.long) features: dict[str, torch.Tensor] = super().__call__(features) bsz, seq_len = features["input_ids"].shape[:2] model_type = getattr(self.model.config, "model_type", None) if self.model is not None else None is_omni = model_type in [ "qwen2_5_omni_thinker", "qwen3_omni_moe_thinker", ] if self.get_rope_func is not None: # for mmrope situation, we should calculate position_ids and rope_deltas per sample. # When neat_packing is on, each sample has packing_params; None means no packing for that sample. boundaries_list = [ p.get("sequence_boundaries") if p is not None else None for p in packing_params_list ] has_packing = any(b is not None and len(b) > 2 for b in boundaries_list) if has_dummy_image and has_packing: # FIXME: too tricky, need to be refactored features["has_dummy_image"] = True # When fake image/audio was injected, sequence_boundaries no longer match the tensor; use non-packing path. if not has_packing: self._compute_rope_position_ids(features, mm_inputs) else: if is_omni: raise RuntimeError("Omni models are not supported for packed sequences for now.") self._compute_rope_position_ids_with_packing( features, mm_inputs, packing_params_list, batch_imglens, batch_vidlens, batch_audlens, has_dummy_image, ) # For transformers compatibility, after https://github.com/huggingface/transformers/issues/39400 if features["position_ids"].dim() == 3: features["position_ids"] = torch.cat( [features["position_ids"][0].unsqueeze(0), features["position_ids"]], dim=0 ) if ( self.model is not None and getattr(self.model.config, "model_type", None) in MROPE_MODELS and ("position_ids" not in features or features["position_ids"].dim() != 3) ): raise ValueError(f"{self.model.config.model_type} requires 3D position ids for mrope.") if "cross_attention_mask" in mm_inputs: # for mllama inputs when pad_to_multiple_of is enabled cross_attention_mask = mm_inputs.pop("cross_attention_mask") seq_len = features["input_ids"].size(1) orig_len = cross_attention_mask.size(1) mm_inputs["cross_attention_mask"] = F.pad(cross_attention_mask, (0, 0, 0, 0, 0, seq_len - orig_len)) features.update(mm_inputs) if "image_bound" in features: # for minicpmv inputs bsz, seq_length = features["input_ids"].shape features["position_ids"] = torch.arange(seq_length).long().repeat(bsz, 1) return {"data": features, "input_ids": features["input_ids"], "labels": features["labels"]} return features @dataclass class SFTDataCollatorWith4DAttentionMask(MultiModalDataCollatorForSeq2Seq): r"""Data collator for 4d attention mask.""" block_diag_attn: bool = False attn_implementation: Literal["eager", "sdpa", "flash_attention_2"] = "eager" compute_dtype: "torch.dtype" = torch.float32 neat_packing: bool = False def __post_init__(self): super().__post_init__() if self.neat_packing and self.attn_implementation == "flash_attention_2": if self.model is not None and getattr(self.model.config, "model_type", None) in ["qwen3_5", "qwen3_5_moe", "gpt_oss"]: raise ValueError("Neat packing is not supported for qwen3_5, qwen3_5_moe, gpt_oss models for now.") @staticmethod def _unpad_packed_features(features: dict[str, Any]) -> None: r"""Trim padded positions for packed FA2 batches.""" attention_mask = features.get("attention_mask") if not torch.is_tensor(attention_mask) or attention_mask.dim() != 2 or attention_mask.size(0) != 1: return seq_len = attention_mask.size(1) non_padding_indices = torch.nonzero(attention_mask[0] != 0, as_tuple=False).flatten() if non_padding_indices.numel() == seq_len: return keys_on_seq_dim_1 = {"input_ids", "labels", "attention_mask", "token_type_ids"} for key, value in list(features.items()): if not torch.is_tensor(value): continue if key == "position_ids" and value.size(-1) == seq_len: features[key] = value.index_select(-1, non_padding_indices) elif key == "cross_attention_mask" and value.dim() >= 2 and value.size(0) == 1 and value.size(1) == seq_len: features[key] = value.index_select(1, non_padding_indices) elif key in keys_on_seq_dim_1 and value.dim() == 2 and value.size(0) == 1 and value.size(1) == seq_len: features[key] = value.index_select(1, non_padding_indices) def __call__(self, features: list[dict[str, Any]]) -> dict[str, "torch.Tensor"]: features = super().__call__(features) has_dummy_image = features.pop("has_dummy_image", False) if self.block_diag_attn and self.attn_implementation != "flash_attention_2": features["attention_mask"] = prepare_4d_attention_mask(features["attention_mask"], self.compute_dtype) if self.neat_packing and self.attn_implementation == "flash_attention_2": # FIXME compatibility fa3/fa4 assert features["input_ids"].shape[0] == 1, "bsz should be 1 for neat packing" if not has_dummy_image: self._unpad_packed_features(features) features["attention_mask"] = None # let transformers handle causal packed mask. for key, value in features.items(): # cast data dtype for paligemma if torch.is_tensor(value) and torch.is_floating_point(value): features[key] = value.to(self.compute_dtype) return features @dataclass class PairwiseDataCollatorWithPadding(MultiModalDataCollatorForSeq2Seq): r"""Data collator for pairwise data.""" def __call__(self, features: list[dict[str, Any]]) -> dict[str, "torch.Tensor"]: r"""Pad batched data to the longest sequence in the batch. We generate 2 * n examples where the first n examples represent chosen examples and the last n examples represent rejected examples. """ concatenated_features = [] for key in ("chosen", "rejected"): for feature in features: target_feature = { "input_ids": feature[f"{key}_input_ids"], "attention_mask": feature[f"{key}_attention_mask"], "labels": feature[f"{key}_labels"], "images": feature["images"], "videos": feature["videos"], "audios": feature["audios"], } concatenated_features.append(target_feature) return super().__call__(concatenated_features) @dataclass class KTODataCollatorWithPadding(MultiModalDataCollatorForSeq2Seq): r"""Data collator for KTO data.""" def __call__(self, features: list[dict[str, Any]]) -> dict[str, "torch.Tensor"]: target_features = [] kl_features = [] kto_tags = [] for feature in features: target_feature = { "input_ids": feature["input_ids"], "attention_mask": feature["attention_mask"], "labels": feature["labels"], "images": feature["images"], "videos": feature["videos"], "audios": feature["audios"], } kl_feature = { "input_ids": feature["kl_input_ids"], "attention_mask": feature["kl_attention_mask"], "labels": feature["kl_labels"], "images": feature["images"], "videos": feature["videos"], "audios": feature["audios"], } target_features.append(target_feature) kl_features.append(kl_feature) kto_tags.append(feature["kto_tags"]) batch = super().__call__(target_features) kl_batch = super().__call__(kl_features) batch["kl_input_ids"] = kl_batch["input_ids"] batch["kl_attention_mask"] = kl_batch["attention_mask"] batch["kl_labels"] = kl_batch["labels"] if "cross_attention_mask" in kl_batch: # for mllama inputs batch["kl_cross_attention_mask"] = kl_batch["cross_attention_mask"] if "token_type_ids" in kl_batch: batch["kl_token_type_ids"] = kl_batch["token_type_ids"] batch["kto_tags"] = torch.tensor(kto_tags) return batch