[breaking change] refactor data pipeline (#6901)

* refactor data

* rename file

Former-commit-id: 7a1a4ce6451cb782573d0bd9dd27a5e443e3a18b

src/llamafactory/data/processor/pairwise.py

@@ -0,0 +1,118 @@
+# Copyright 2025 the LlamaFactory team.
+#
+# 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.
+
+from collections import defaultdict
+from typing import TYPE_CHECKING, Any, Dict, List, Optional, Sequence, Tuple
+
+from ...extras import logging
+from ...extras.constants import IGNORE_INDEX
+from .processor_utils import DatasetProcessor, infer_seqlen
+
+
+if TYPE_CHECKING:
+    from ..mm_plugin import AudioInput, ImageInput, VideoInput
+
+
+logger = logging.get_logger(__name__)
+
+
+class PairwiseDatasetProcessor(DatasetProcessor):
+    def _encode_data_example(
+        self,
+        prompt: Sequence[Dict[str, str]],
+        response: Sequence[Dict[str, str]],
+        system: Optional[str],
+        tools: Optional[str],
+        images: Sequence["ImageInput"],
+        videos: Sequence["VideoInput"],
+        audios: Sequence["AudioInput"],
+    ) -> Tuple[List[int], List[int], List[int], List[int]]:
+        chosen_messages = self.template.mm_plugin.process_messages(
+            prompt + [response[0]], images, videos, audios, self.processor
+        )
+        rejected_messages = self.template.mm_plugin.process_messages(
+            prompt + [response[1]], images, videos, audios, self.processor
+        )
+        prompt_ids, chosen_ids = self.template.encode_oneturn(self.tokenizer, chosen_messages, system, tools)
+        _, rejected_ids = self.template.encode_oneturn(self.tokenizer, rejected_messages, system, tools)
+
+        if self.template.efficient_eos:
+            chosen_ids += [self.tokenizer.eos_token_id]
+            rejected_ids += [self.tokenizer.eos_token_id]
+
+        prompt_ids, _ = self.template.mm_plugin.process_token_ids(
+            prompt_ids, None, images, videos, audios, self.tokenizer, self.processor
+        )
+        # consider the response is more important
+        source_len, target_len = infer_seqlen(
+            len(prompt_ids), max(len(chosen_ids), len(rejected_ids)), self.data_args.cutoff_len
+        )
+        prompt_ids = prompt_ids[:source_len]
+        chosen_ids = chosen_ids[:target_len]
+        rejected_ids = rejected_ids[:target_len]
+
+        chosen_input_ids = prompt_ids + chosen_ids
+        chosen_labels = [IGNORE_INDEX] * source_len + chosen_ids
+        rejected_input_ids = prompt_ids + rejected_ids
+        rejected_labels = [IGNORE_INDEX] * source_len + rejected_ids
+        return chosen_input_ids, chosen_labels, rejected_input_ids, rejected_labels
+
+    def preprocess_dataset(self, examples: Dict[str, List[Any]]) -> Dict[str, List[Any]]:
+        # build input pairs with format `<bos> X`, `Y1 <eos>` and `Y2 <eos>`
+        model_inputs = defaultdict(list)
+        for i in range(len(examples["_prompt"])):
+            if len(examples["_prompt"][i]) % 2 != 1 or len(examples["_response"][i]) < 2:
+                logger.warning_rank0(
+                    "Dropped invalid example: {}".format(examples["_prompt"][i] + examples["_response"][i])
+                )
+                continue
+
+            chosen_input_ids, chosen_labels, rejected_input_ids, rejected_labels = self._encode_data_example(
+                prompt=examples["_prompt"][i],
+                response=examples["_response"][i],
+                system=examples["_system"][i],
+                tools=examples["_tools"][i],
+                images=examples["_images"][i] or [],
+                videos=examples["_videos"][i] or [],
+                audios=examples["_audios"][i] or [],
+            )
+            model_inputs["chosen_input_ids"].append(chosen_input_ids)
+            model_inputs["chosen_attention_mask"].append([1] * len(chosen_input_ids))
+            model_inputs["chosen_labels"].append(chosen_labels)
+            model_inputs["rejected_input_ids"].append(rejected_input_ids)
+            model_inputs["rejected_attention_mask"].append([1] * len(rejected_input_ids))
+            model_inputs["rejected_labels"].append(rejected_labels)
+            model_inputs["images"].append(examples["_images"][i])
+            model_inputs["videos"].append(examples["_videos"][i])
+            model_inputs["audios"].append(examples["_audios"][i])
+
+        return model_inputs
+
+    def print_data_example(self, example: Dict[str, List[int]]) -> None:
+        valid_chosen_labels = list(filter(lambda x: x != IGNORE_INDEX, example["chosen_labels"]))
+        valid_rejected_labels = list(filter(lambda x: x != IGNORE_INDEX, example["rejected_labels"]))
+        print("chosen_input_ids:\n{}".format(example["chosen_input_ids"]))
+        print(
+            "chosen_inputs:\n{}".format(self.tokenizer.decode(example["chosen_input_ids"], skip_special_tokens=False))
+        )
+        print("chosen_label_ids:\n{}".format(example["chosen_labels"]))
+        print(f"chosen_labels:\n{self.tokenizer.decode(valid_chosen_labels, skip_special_tokens=False)}")
+        print("rejected_input_ids:\n{}".format(example["rejected_input_ids"]))
+        print(
+            "rejected_inputs:\n{}".format(
+                self.tokenizer.decode(example["rejected_input_ids"], skip_special_tokens=False)
+            )
+        )
+        print("rejected_label_ids:\n{}".format(example["rejected_labels"]))
+        print(f"rejected_labels:\n{self.tokenizer.decode(valid_rejected_labels, skip_special_tokens=False)}")