trl/trainer/kto_trainer.py

# Copyright 2020-2025 The HuggingFace Team. All rights reserved.
#
# 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 inspect
import os
import random
import textwrap
import warnings
from collections import defaultdict
from contextlib import contextmanager, nullcontext
from operator import itemgetter
from pathlib import Path
from typing import TYPE_CHECKING, Any, Callable, Literal, Optional, Union

import numpy as np
import pandas as pd
import torch
import torch.nn as nn
import torch.nn.functional as F
from accelerate import PartialState
from accelerate.utils import tqdm
from datasets import Dataset, concatenate_datasets
from torch import autocast
from torch.utils.data import DataLoader, SequentialSampler
from transformers import (
    AutoModelForCausalLM,
    BaseImageProcessor,
    DataCollator,
    FeatureExtractionMixin,
    PreTrainedModel,
    PreTrainedTokenizerBase,
    ProcessorMixin,
    Trainer,
    TrainerCallback,
    TrainingArguments,
    is_comet_available,
    is_wandb_available,
)
from transformers.trainer_utils import EvalLoopOutput, has_length
from transformers.utils import is_peft_available

from ..data_utils import maybe_apply_chat_template, maybe_extract_prompt, maybe_unpair_preference_dataset
from ..import_utils import is_liger_kernel_available
from ..models import create_reference_model, prepare_deepspeed
from .kto_config import KTOConfig
from .utils import (
    DPODataCollatorWithPadding,
    disable_dropout_in_model,
    generate_model_card,
    get_comet_experiment_url,
    log_table_to_comet_experiment,
    pad_to_length,
    peft_module_casting_to_bf16,
    selective_log_softmax,
)


if is_liger_kernel_available():
    from liger_kernel.chunked_loss import LigerFusedLinearKTOLoss

if is_peft_available():
    from peft import PeftModel, get_peft_model, prepare_model_for_kbit_training

if is_wandb_available():
    import wandb


if TYPE_CHECKING:
    from transformers import PreTrainedModel, PreTrainedTokenizer

RUNNING_NAME = "running.pt"


def _get_kl_dataset(batch: dict[str, list[Any]]) -> dict[str, list[Any]]:
    """
    Creates mismatched pairs of prompts and completions for the KL dataset by adding a +1 offset to the order of completions.
    For best results, the mismatched outputs y' used to estimate the KL term for a batch should be the same set as the matched
    outputs y used to estimate the rewards in that batch, just paired with different x.
    """
    batch["answer_input_ids"] = [batch["answer_input_ids"][-1]] + batch["answer_input_ids"][:-1]
    batch["answer_attention_mask"] = [batch["answer_attention_mask"][-1]] + batch["answer_attention_mask"][:-1]
    return batch


def _tokenize(
    batch: dict[str, list[Any]],
    tokenizer: "PreTrainedTokenizer",
) -> dict[str, list[Any]]:
    """Tokenize a batch from a KTO specific dataset."""
    prompt_tokenized = tokenizer(batch["prompt"], add_special_tokens=False)
    prompt_input_ids = prompt_tokenized["input_ids"]
    prompt_attention_mask = prompt_tokenized["attention_mask"]
    prompt_and_completion = [prompt + completion for prompt, completion in zip(batch["prompt"], batch["completion"])]
    full_tokenized = tokenizer(prompt_and_completion, add_special_tokens=False)
    full_input_ids = full_tokenized["input_ids"]
    full_attention_mask = full_tokenized["attention_mask"]

    answer_input_ids = [f[len(p) :] for f, p in zip(full_input_ids, prompt_input_ids)]
    answer_attention_mask = [f[len(p) :] for f, p in zip(full_attention_mask, prompt_attention_mask)]

    # Concat tokens to form `enc(a) + enc(a + b)[len(enc(a)):]`
    full_concat_input_ids = [np.concatenate([p, a]) for p, a in zip(prompt_input_ids, answer_input_ids)]
    # Prepare input tokens for token by token comparison
    full_input_ids = [np.array(f) for f in full_input_ids]
    for full, concat in zip(full_input_ids, full_concat_input_ids):
        if len(full) != len(concat):
            raise ValueError(
                "The elements in 'full_input_ids' and 'full_concat_input_ids' must have the same pairwise length."
            )

    # On some tokenizers, like Llama-2 tokenizer, there are occasions where tokens
    # can be merged together when tokenizing prompt+answer. This could result
    # on the last token from the prompt being different when tokenized on its own
    # vs when done as prompt+answer.
    response_token_ids_start_idx = [len(p) for p in prompt_input_ids]

    # If tokenized prompt is different than both prompt+answer, then it means the
    # last token has changed due to merging.
    for idx, (p, f, r) in enumerate(zip(prompt_input_ids, full_input_ids, response_token_ids_start_idx)):
        if not np.array_equal(p, f[:r]):
            response_token_ids_start_idx[idx] -= 1

    prompt_input_ids = [f[:r] for f, r in zip(full_input_ids, response_token_ids_start_idx)]
    prompt_attention_mask = [f[:r] for f, r in zip(full_attention_mask, response_token_ids_start_idx)]

    for p, m in zip(prompt_input_ids, prompt_attention_mask):
        if len(p) != len(m):
            raise ValueError("Prompt input ids and attention mask should have the same length.")

    answer_input_ids = [f[r:] for f, r in zip(full_input_ids, response_token_ids_start_idx)]
    answer_attention_mask = [f[r:] for f, r in zip(full_attention_mask, response_token_ids_start_idx)]

    output = dict(
        prompt_input_ids=prompt_input_ids,
        prompt_attention_mask=prompt_attention_mask,
        answer_input_ids=answer_input_ids,
        answer_attention_mask=answer_attention_mask,
    )

    return output


def _process_tokens(example: dict[str, Any], model: "PreTrainedModel" = None, **kwargs) -> dict:
    """Process tokens of a KTO specific dataset.

    At this stage, we don't convert to PyTorch tensors yet; we just handle the truncation
    in case the prompt + completion responses is/are too long. First
    we truncate the prompt; if we're still too long, we truncate the completion.

    We also create the labels for the completion responses, which are of length equal to
    the sum of the length of the prompt and the completion response, with
    label_pad_token_id  for the prompt tokens.
    """
    prompt = example["prompt"]
    completion = example["completion"]

    batch = {
        f"{kwargs['prefix']}prompt": prompt,
        f"{kwargs['prefix']}completion": completion,
        f"{kwargs['prefix']}label": example["label"],
    }

    if not kwargs["is_encoder_decoder"]:
        # Check issues below for more details
        #  1. https://github.com/huggingface/trl/issues/907
        #  2. https://github.com/EleutherAI/lm-evaluation-harness/pull/531#issuecomment-1595586257
        #  3. https://github.com/LianjiaTech/BELLE/issues/337

        if not isinstance(prompt, str):
            raise ValueError(f"prompt should be an str but got {type(prompt)}")

        if not isinstance(completion, str):
            raise ValueError(f"completion should be an str but got {type(completion)}")

        # keys of format prompt_* refers to just the prompt and answer_* refers to just the answer
        all_tokens = {
            "prompt_input_ids": example["prompt_input_ids"],
            "prompt_attention_mask": example["prompt_attention_mask"],
            "answer_input_ids": example["answer_input_ids"],
            "answer_attention_mask": example["answer_attention_mask"],
        }

        # calculate max length by checking if BOS/EOS is already there
        max_length = kwargs["max_length"]
        bos_token_id = kwargs["tokenizer"].bos_token_id
        eos_token_id = kwargs["tokenizer"].eos_token_id
        if len(all_tokens["prompt_input_ids"]) > 0 and bos_token_id != all_tokens["prompt_input_ids"][0]:
            max_length -= 1
        if len(all_tokens["answer_input_ids"]) > 0 and eos_token_id != all_tokens["answer_input_ids"][-1]:
            max_length -= 1

        # if combined sequence is too long (> max_length - 1 for BOS token - 1 for EOS), truncate the prompt
        if len(all_tokens["prompt_input_ids"]) + len(all_tokens["answer_input_ids"]) > max_length:
            for k in ["prompt_input_ids", "prompt_attention_mask"]:
                if kwargs["truncation_mode"] == "keep_start":
                    all_tokens[k] = all_tokens[k][: kwargs["max_prompt_length"]]
                elif kwargs["truncation_mode"] == "keep_end":
                    all_tokens[k] = all_tokens[k][-kwargs["max_prompt_length"] :]
                else:
                    raise ValueError(f"Unknown truncation mode: {kwargs['truncation_mode']}")

        # if that's still too long, truncate the response
        if len(all_tokens["prompt_input_ids"]) + len(all_tokens["answer_input_ids"]) > max_length:
            for k in ["answer_input_ids", "answer_attention_mask"]:
                all_tokens[k] = all_tokens[k][: max_length - kwargs["max_prompt_length"]]

        # all input_ids and attention mask as is. We then check if we need to add BOS/EOS tokens
        batch[f"{kwargs['prefix']}prompt_input_ids"] = all_tokens["prompt_input_ids"]
        batch[f"{kwargs['prefix']}prompt_attention_mask"] = all_tokens["prompt_attention_mask"]
        batch[f"{kwargs['prefix']}completion_input_ids"] = (
            all_tokens["prompt_input_ids"] + all_tokens["answer_input_ids"]
        )
        batch[f"{kwargs['prefix']}completion_attention_mask"] = (
            all_tokens["prompt_attention_mask"] + all_tokens["answer_attention_mask"]
        )

        # add BOS, which affects both prompt and the full completion
        if bos_token_id is not None:
            if len(all_tokens["prompt_input_ids"]) == 0 or bos_token_id != all_tokens["prompt_input_ids"][0]:
                batch[f"{kwargs['prefix']}prompt_input_ids"] = [bos_token_id] + batch[
                    f"{kwargs['prefix']}prompt_input_ids"
                ]
                batch[f"{kwargs['prefix']}prompt_attention_mask"] = [1] + batch[
                    f"{kwargs['prefix']}prompt_attention_mask"
                ]
                batch[f"{kwargs['prefix']}completion_input_ids"] = [bos_token_id] + batch[
                    f"{kwargs['prefix']}completion_input_ids"
                ]
                batch[f"{kwargs['prefix']}completion_attention_mask"] = [1] + batch[
                    f"{kwargs['prefix']}completion_attention_mask"
                ]
        # add EOS, which affects only the full completion
        if len(all_tokens["answer_input_ids"]) == 0 or eos_token_id != all_tokens["answer_input_ids"][-1]:
            batch[f"{kwargs['prefix']}completion_input_ids"] = batch[f"{kwargs['prefix']}completion_input_ids"] + [
                eos_token_id
            ]
            batch[f"{kwargs['prefix']}completion_attention_mask"] = batch[
                f"{kwargs['prefix']}completion_attention_mask"
            ] + [1]

        batch[f"{kwargs['prefix']}completion_labels"] = batch[f"{kwargs['prefix']}completion_input_ids"][:]
        batch[f"{kwargs['prefix']}completion_labels"][: len(batch[f"{kwargs['prefix']}prompt_input_ids"])] = [
            kwargs["label_pad_token_id"]
        ] * len(batch[f"{kwargs['prefix']}prompt_input_ids"])
    else:
        completion_tokens = kwargs["tokenizer"](
            completion, truncation=True, max_length=kwargs["max_completion_length"], add_special_tokens=True
        )
        prompt_tokens = kwargs["tokenizer"](
            prompt, truncation=True, max_length=kwargs["max_prompt_length"], add_special_tokens=True
        )

        batch[f"{kwargs['prefix']}prompt_input_ids"] = prompt_tokens["input_ids"]
        batch[f"{kwargs['prefix']}prompt_attention_mask"] = prompt_tokens["attention_mask"]

        batch[f"{kwargs['prefix']}completion_labels"] = completion_tokens["input_ids"]
        batch[f"{kwargs['prefix']}completion_attention_mask"] = completion_tokens["attention_mask"]
        if model is not None and hasattr(model, "prepare_decoder_input_ids_from_labels"):
            batch[f"{kwargs['prefix']}completion_decoder_input_ids"] = model.prepare_decoder_input_ids_from_labels(
                labels=torch.tensor(batch["completion_labels"])
            )

    return batch


class KTOTrainer(Trainer):
    r"""
    Initialize KTOTrainer.

    Args:
        model (`transformers.PreTrainedModel`):
            The model to train, preferably an `AutoModelForSequenceClassification`.
        ref_model (`PreTrainedModelWrapper`):
            Hugging Face transformer model with a casual language modelling head. Used for implicit reward computation and loss. If no
            reference model is provided, the trainer will create a reference model with the same architecture as the model to be optimized.
        args (`KTOConfig`):
            The arguments to use for training.
        train_dataset (`datasets.Dataset`):
            The dataset to use for training.
        eval_dataset (`datasets.Dataset`):
            The dataset to use for evaluation.
        processing_class (`PreTrainedTokenizerBase` or `BaseImageProcessor` or `FeatureExtractionMixin` or `ProcessorMixin`, *optional*):
            Processing class used to process the data. If provided, will be used to automatically process the inputs
            for the model, and it will be saved along the model to make it easier to rerun an interrupted training or
            reuse the fine-tuned model.
        data_collator (`transformers.DataCollator`, *optional*, defaults to `None`):
            The data collator to use for training. If None is specified, the default data collator (`DPODataCollatorWithPadding`) will be used
            which will pad the sequences to the maximum length of the sequences in the batch, given a dataset of paired sequences.
        model_init (`Callable[[], transformers.PreTrainedModel]`):
            The model initializer to use for training. If None is specified, the default model initializer will be used.
        callbacks (`list[transformers.TrainerCallback]`):
            The callbacks to use for training.
        optimizers (`tuple[torch.optim.Optimizer, torch.optim.lr_scheduler.LambdaLR]`):
            The optimizer and scheduler to use for training.
        preprocess_logits_for_metrics (`Callable[[torch.Tensor, torch.Tensor], torch.Tensor]`):
            The function to use to preprocess the logits before computing the metrics.
        peft_config (`dict`, defaults to `None`):
            The PEFT configuration to use for training. If you pass a PEFT configuration, the model will be wrapped in a PEFT model.
        compute_metrics (`Callable[[EvalPrediction], dict]`, *optional*):
            The function to use to compute the metrics. Must take a `EvalPrediction` and return
            a dictionary string to metric values.
        model_adapter_name (`str`, defaults to `None`):
            Name of the train target PEFT adapter, when using LoRA with multiple adapters.
        ref_adapter_name (`str`, defaults to `None`):
            Name of the reference PEFT adapter, when using LoRA with multiple adapters.
    """

    _tag_names = ["trl", "kto"]

    def __init__(
        self,
        model: Union[PreTrainedModel, nn.Module, str] = None,
        ref_model: Optional[Union[PreTrainedModel, nn.Module, str]] = None,
        args: KTOConfig = None,
        train_dataset: Optional[Dataset] = None,
        eval_dataset: Optional[Union[Dataset, dict[str, Dataset]]] = None,
        processing_class: Optional[
            Union[PreTrainedTokenizerBase, BaseImageProcessor, FeatureExtractionMixin, ProcessorMixin]
        ] = None,
        data_collator: Optional[DataCollator] = None,
        model_init: Optional[Callable[[], PreTrainedModel]] = None,
        callbacks: Optional[list[TrainerCallback]] = None,
        optimizers: tuple[torch.optim.Optimizer, torch.optim.lr_scheduler.LambdaLR] = (None, None),
        preprocess_logits_for_metrics: Optional[Callable[[torch.Tensor, torch.Tensor], torch.Tensor]] = None,
        peft_config: Optional[dict] = None,
        compute_metrics: Optional[Callable[[EvalLoopOutput], dict]] = None,
        model_adapter_name: Optional[str] = None,
        ref_adapter_name: Optional[str] = None,
    ):
        if type(args) is TrainingArguments:
            raise ValueError("Please use `KTOConfig` instead TrainingArguments.")

        if not isinstance(model, str) and ref_model is model:
            raise ValueError(
                "`model` and `ref_model` cannot be the same object. If you want `ref_model` to be the "
                "same as `model`, you must mass a copy of it, or `None` if you use peft."
            )

        if args.model_init_kwargs is None:
            model_init_kwargs = {}
        elif not isinstance(model, str):
            raise ValueError("You passed model_kwargs to the KTOTrainer. But your model is already instantiated.")
        else:
            model_init_kwargs = args.model_init_kwargs
            torch_dtype = model_init_kwargs.get("torch_dtype")
            if torch_dtype is not None:
                # Convert to `torch.dtype` if an str is passed
                if isinstance(torch_dtype, str) and torch_dtype != "auto":
                    torch_dtype = getattr(torch, torch_dtype)
                if torch_dtype != "auto" and not isinstance(torch_dtype, torch.dtype):
                    raise ValueError(
                        f"Invalid `torch_dtype` passed to the KTOConfig. Expected a string with either `torch.dtype` or 'auto', but got {torch_dtype}."
                    )
                model_init_kwargs["torch_dtype"] = torch_dtype

        if args.ref_model_init_kwargs is None:
            ref_model_init_kwargs = {}
        elif not isinstance(ref_model, str):
            raise ValueError(
                "You passed ref_model_kwargs to the KTOTrainer. But your ref_model is already instantiated."
            )
        else:
            ref_model_init_kwargs = args.ref_model_init_kwargs
            torch_dtype = ref_model_init_kwargs.get("torch_dtype")
            if torch_dtype is not None:
                # Convert to `torch.dtype` if an str is passed
                if isinstance(torch_dtype, str) and torch_dtype != "auto":
                    torch_dtype = getattr(torch, torch_dtype)
                if torch_dtype != "auto" and not isinstance(torch_dtype, torch.dtype):
                    raise ValueError(
                        f"Invalid `torch_dtype` passed to the KTOConfig. Expected a string with either `torch.dtype` or 'auto', but got {torch_dtype}."
                    )
                ref_model_init_kwargs["torch_dtype"] = torch_dtype

        if isinstance(model, str):
            model = AutoModelForCausalLM.from_pretrained(model, **model_init_kwargs)

        if isinstance(ref_model, str):
            ref_model = AutoModelForCausalLM.from_pretrained(ref_model, **ref_model_init_kwargs)

        # Initialize this variable to False. This helps tracking the case when `peft_module_casting_to_bf16`
        # has been called in order to properly call autocast if needed.
        self._peft_has_been_casted_to_bf16 = False

        if not is_peft_available() and peft_config is not None:
            raise ValueError(
                "PEFT is not installed and you passed a `peft_config` in the trainer's kwargs, please install it with `pip install peft` to use the PEFT models"
            )
        elif is_peft_available() and peft_config is not None:
            # if model is a peft model and we have a peft_config, we merge and unload it first
            if isinstance(model, PeftModel):
                model = model.merge_and_unload()

            if getattr(model, "is_loaded_in_8bit", False) or getattr(model, "is_loaded_in_4bit", False):
                _support_gc_kwargs = hasattr(
                    args, "gradient_checkpointing_kwargs"
                ) and "gradient_checkpointing_kwargs" in list(
                    inspect.signature(prepare_model_for_kbit_training).parameters
                )

                prepare_model_kwargs = {"use_gradient_checkpointing": args.gradient_checkpointing}

                if _support_gc_kwargs:
                    prepare_model_kwargs["gradient_checkpointing_kwargs"] = args.gradient_checkpointing_kwargs

                model = prepare_model_for_kbit_training(model, **prepare_model_kwargs)
            elif args.gradient_checkpointing:
                # For backward compatibility with older versions of transformers
                if hasattr(model, "enable_input_require_grads"):
                    model.enable_input_require_grads()
                else:

                    def make_inputs_require_grad(module, input, output):
                        output.requires_grad_(True)

                    model.get_input_embeddings().register_forward_hook(make_inputs_require_grad)

            # get peft model with the given config
            model = get_peft_model(model, peft_config)
            if args.bf16 and getattr(model, "is_loaded_in_4bit", False):
                peft_module_casting_to_bf16(model)
                # If args.bf16 we need to explicitly call `generate` with torch amp autocast context manager
                self._peft_has_been_casted_to_bf16 = True

        # For models that use gradient_checkpointing, we need to attach a hook that enables input
        # to explicitly have `requires_grad=True`, otherwise training will either silently
        # fail or completely fail.
        elif args.gradient_checkpointing:
            # For backward compatibility with older versions of transformers
            if hasattr(model, "enable_input_require_grads"):
                model.enable_input_require_grads()
            else:

                def make_inputs_require_grad(module, input, output):
                    output.requires_grad_(True)

                model.get_input_embeddings().register_forward_hook(make_inputs_require_grad)

        if args.generate_during_eval and not (is_wandb_available() or is_comet_available()):
            raise ValueError(
                "`generate_during_eval=True` requires Weights and Biases or Comet to be installed."
                " Please install `wandb` or `comet-ml` to resolve."
            )

        if model is not None:
            self.is_encoder_decoder = model.config.is_encoder_decoder
        elif args.is_encoder_decoder is None:
            raise ValueError("When no model is provided, you need to pass the parameter is_encoder_decoder.")
        else:
            self.is_encoder_decoder = args.is_encoder_decoder

        self.is_peft_model = is_peft_available() and isinstance(model, PeftModel)
        self.model_adapter_name = model_adapter_name
        self.ref_adapter_name = ref_adapter_name

        if ref_model:
            self.ref_model = ref_model
        elif self.is_peft_model or args.precompute_ref_log_probs:
            # The `model` with adapters turned off will be used as the reference model
            self.ref_model = None
        else:
            self.ref_model = create_reference_model(model)

        if processing_class is None:
            raise ValueError(
                "max_length or a processing_class must be specified when using the default DPODataCollatorWithPadding"
            )
        if args.max_length is None:
            warnings.warn(
                "When using DPODataCollatorWithPadding, you should set `max_length` in the KTOTrainer's init"
                " it will be set to `512` by default, but you should do it yourself in the future.",
                UserWarning,
            )
            max_length = 512
        if args.max_length is not None:
            max_length = args.max_length

        if args.max_prompt_length is None:
            warnings.warn(
                "When using DPODataCollatorWithPadding, you should set `max_prompt_length` in the KTOTrainer's init"
                " it will be set to `128` by default, but you should do it yourself in the future.",
                UserWarning,
            )
            max_prompt_length = 128
        if args.max_prompt_length is not None:
            max_prompt_length = args.max_prompt_length

        max_completion_length = None
        if args.max_completion_length is None and self.is_encoder_decoder:
            warnings.warn(
                "When using DPODataCollatorWithPadding with an encoder decoder architecture, you should set `max_completion_length` in the KTOTrainer's init"
                " it will be set to `128` by default, but you should do it yourself in the future.",
                UserWarning,
            )
            max_completion_length = 128
        if args.max_completion_length is not None and self.is_encoder_decoder:
            max_completion_length = args.max_completion_length

        if data_collator is None:
            data_collator = DPODataCollatorWithPadding(
                pad_token_id=processing_class.pad_token_id,
                label_pad_token_id=args.label_pad_token_id,
                is_encoder_decoder=self.is_encoder_decoder,
            )

            if args.remove_unused_columns:
                args.remove_unused_columns = False
                # warn users
                warnings.warn(
                    "When using DPODataCollatorWithPadding, you should set `remove_unused_columns=False` in your KTOConfig"
                    " we have set it for you, but you should do it yourself in the future.",
                    UserWarning,
                )

            self.use_dpo_data_collator = True
        else:
            self.use_dpo_data_collator = False

        # Disable dropout in the model and reference model
        if args.disable_dropout:
            disable_dropout_in_model(model)
            if self.ref_model is not None:
                disable_dropout_in_model(self.ref_model)

        self.loss_type = args.loss_type
        self.max_length = max_length
        self.generate_during_eval = args.generate_during_eval
        self.label_pad_token_id = args.label_pad_token_id
        self.padding_value = args.padding_value if args.padding_value is not None else processing_class.pad_token_id
        self.max_prompt_length = max_prompt_length
        self.truncation_mode = args.truncation_mode
        self.max_completion_length = max_completion_length
        self.processing_class = processing_class
        self.precompute_ref_log_probs = args.precompute_ref_log_probs

        # Not all losses require a KL calculation
        self.calculate_KL = True
        if self.loss_type in ["apo_zero_unpaired"]:
            self.calculate_KL = False

        # Since ref_logs are precomputed on the first call to get_train/eval_dataloader
        # keep track of first called to avoid computation of future calls
        self._precomputed_train_ref_log_probs = False
        self._precomputed_eval_ref_log_probs = False

        # metric
        self._stored_metrics = defaultdict(lambda: defaultdict(list))

        # KTO parameter
        self.beta = args.beta
        self.desirable_weight = args.desirable_weight
        self.undesirable_weight = args.undesirable_weight
        self.aux_loss_enabled = getattr(model.config, "output_router_logits", False)
        self.aux_loss_coef = getattr(model.config, "router_aux_loss_coef", 0.0)
        if self.aux_loss_enabled and self.aux_loss_coef == 0.0:
            warnings.warn(
                "You set `output_router_logits` to `True` in the model config, but `router_aux_loss_coef` is set to "
                "`0.0`, meaning the auxiliary loss will not be used. Either set `router_aux_loss_coef` to a value "
                "greater than `0.0`, or set `output_router_logits` to `False` if you don't want to use the auxiliary "
                "loss.",
                UserWarning,
            )

        # The trainer estimates the number of FLOPs (floating-point operations) using the number of elements in the
        # input tensor associated with the key "input_ids". However, in KTO, the sampled data does not include the
        # "input_ids" key. Instead, the available keys are "prompt_input_ids" and "completion_input_ids". As a result,
        # the trainer issues the warning: "Could not estimate the number of tokens of the input, floating-point
        # operations will not be computed." To suppress this warning, we set the "estimate_tokens" key in the model's
        # "warnings_issued" dictionary to True. This acts as a flag to indicate that the warning has already been
        # issued.
        model.warnings_issued["estimate_tokens"] = True

        # Compute that only on the main process for faster data processing.
        # see: https://github.com/huggingface/trl/pull/1255
        with PartialState().main_process_first():
            # Extract the prompt if needed
            train_dataset = train_dataset.map(
                maybe_extract_prompt, num_proc=args.dataset_num_proc, desc="Extracting prompt from train dataset"
            )
            # Unpair the dataset if needed
            train_dataset = maybe_unpair_preference_dataset(
                train_dataset, args.dataset_num_proc, desc="Unpairing train dataset"
            )
            # Apply the chat template if needed
            train_dataset = train_dataset.map(
                maybe_apply_chat_template,
                fn_kwargs={"tokenizer": processing_class},
                num_proc=args.dataset_num_proc,
                desc="Applying chat template to train dataset",
            )
            if eval_dataset is not None:
                eval_dataset = eval_dataset.map(
                    maybe_extract_prompt, num_proc=args.dataset_num_proc, desc="Extracting prompt from eval dataset"
                )
                eval_dataset = maybe_unpair_preference_dataset(
                    eval_dataset, args.dataset_num_proc, desc="Unpairing eval dataset"
                )
                eval_dataset = eval_dataset.map(
                    maybe_apply_chat_template,
                    fn_kwargs={"tokenizer": processing_class},
                    num_proc=args.dataset_num_proc,
                    desc="Applying chat template to eval dataset",
                )

            # Tokenize and prepare the training datasets
            train_dataset = train_dataset.map(
                _tokenize,
                batched=True,
                fn_kwargs={"tokenizer": self.processing_class},
                num_proc=args.dataset_num_proc,
                desc="Tokenizing train dataset",
            )

            fn_kwargs = {
                "prefix": "",
                "is_encoder_decoder": self.is_encoder_decoder,
                "tokenizer": self.processing_class,
                "max_length": self.max_length,
                "truncation_mode": self.truncation_mode,
                "label_pad_token_id": self.label_pad_token_id,
                "max_prompt_length": self.max_prompt_length,
                "max_completion_length": self.max_completion_length,
            }

            train_dataset = train_dataset.map(
                _process_tokens,
                fn_kwargs=fn_kwargs,
                num_proc=args.dataset_num_proc,
                desc="Processing tokenized train dataset",
            )

            # Tokenize and prepare the eval datasets
            if eval_dataset is not None:
                eval_dataset = eval_dataset.map(
                    _tokenize,
                    fn_kwargs={"tokenizer": self.processing_class},
                    batched=True,
                    num_proc=args.dataset_num_proc,
                    desc="Tokenizing eval dataset",
                )

                eval_dataset = eval_dataset.map(
                    _process_tokens,
                    fn_kwargs=fn_kwargs,
                    num_proc=args.dataset_num_proc,
                    desc="Processing tokenized eval dataset",
                )

            # Get KL datasets if needed
            if self.calculate_KL:
                if args.per_device_train_batch_size <= 1:
                    raise ValueError(
                        "Actual (not effective) batch size must be > 1. KTO will not work properly because the KL term will be equivalent to the implied reward."
                    )

                # create pairs for estimating the KL term by flipping the matched pairs in each batch of size total_batch_size
                # i.e., (x_1, y_1), ..., (x_n, y_n) --> (x_1, y_n), ..., (x_n, y_1) = (x'_1, y'_1), ..., (x'_n, y'_n)
                train_kl_dataset = train_dataset.map(
                    _get_kl_dataset,
                    batched=True,
                    batch_size=args.per_device_train_batch_size,
                    num_proc=args.dataset_num_proc,
                    desc="Extracting KL train dataset",
                )

                fn_kwargs["prefix"] = "KL_"
                train_kl_dataset = train_kl_dataset.map(
                    _process_tokens,
                    fn_kwargs=fn_kwargs,
                    num_proc=args.dataset_num_proc,
                    remove_columns=[c for c in train_kl_dataset.column_names if c in train_dataset.column_names],
                    desc="Processing tokenized train KL dataset",
                )

                # merge the datasets
                train_dataset = concatenate_datasets([train_dataset, train_kl_dataset], axis=1)

                if eval_dataset is not None:
                    # Get KL dataset
                    eval_kl_dataset = eval_dataset.map(
                        _get_kl_dataset,
                        batched=True,
                        batch_size=args.per_device_train_batch_size,
                        num_proc=args.dataset_num_proc,
                        desc="Extracting eval KL dataset",
                    )

                    eval_kl_dataset = eval_kl_dataset.map(
                        _process_tokens,
                        fn_kwargs=fn_kwargs,
                        num_proc=args.dataset_num_proc,
                        remove_columns=[c for c in eval_kl_dataset.column_names if c in eval_dataset.column_names],
                        desc="Processing tokenized eval KL dataset",
                    )

                    # merge the datasets
                    eval_dataset = concatenate_datasets([eval_dataset, eval_kl_dataset], axis=1)

            # calculate dataset desirability balance
            num_desirable = max(sum(train_dataset["label"]), 1)
            num_undesirable = max(len(train_dataset["label"]) - num_desirable, 1)  # "label" is binary

            if num_desirable != num_undesirable:
                # The lower and upper bounds come from Eq. (8) of https://huggingface.co/papers/2402.01306
                des_weight_lower_bound = round((num_undesirable * self.undesirable_weight / num_desirable) * 1, 2)
                des_weight_upper_bound = round((num_undesirable * self.undesirable_weight / num_desirable) * 1.33, 2)
                und_weight_lower_bound = round((num_desirable * self.desirable_weight / num_undesirable) / 1.33, 2)
                und_weight_upper_bound = round((num_desirable * self.desirable_weight / num_undesirable) / 1, 2)

                des_weight_in_range = des_weight_lower_bound <= self.desirable_weight <= des_weight_upper_bound
                und_weight_in_range = und_weight_lower_bound <= self.undesirable_weight <= und_weight_upper_bound

                if not (des_weight_in_range or und_weight_in_range):
                    warnings.warn(
                        "You have different amounts of desirable/positive and undesirable/negative examples but the "
                        "weights on the desirable and undesirable losses don't seem to be in an ideal range. Based "
                        f"on your data, we recommend EITHER "
                        f"desirable_weight in [{des_weight_lower_bound}, {des_weight_upper_bound}] or "
                        f"undesirable_weight in [{und_weight_lower_bound}, {und_weight_upper_bound}] (but NOT BOTH). "
                        "See the documentation on how to optimally set these weights.",
                        UserWarning,
                    )

        super().__init__(
            model=model,
            args=args,
            data_collator=data_collator,
            train_dataset=train_dataset,
            eval_dataset=eval_dataset,
            processing_class=processing_class,
            model_init=model_init,
            compute_metrics=compute_metrics,
            callbacks=callbacks,
            optimizers=optimizers,
            preprocess_logits_for_metrics=preprocess_logits_for_metrics,
        )

        # Gradient accumulation requires scaled loss. Normally, loss scaling in the parent class depends on whether the
        # model accepts loss-related kwargs. Since we compute our own loss, this check is irrelevant. We set
        # self.model_accepts_loss_kwargs to False to enable scaling.
        self.model_accepts_loss_kwargs = False

        # Add tags for models that have been loaded with the correct transformers version
        if hasattr(self.model, "add_model_tags"):
            self.model.add_model_tags(self._tag_names)

        if not hasattr(self, "accelerator"):
            raise AttributeError(
                "Your `Trainer` does not have an `accelerator` object. Consider upgrading `transformers`."
            )

        # Deepspeed Zero-3 does not support precompute_ref_log_probs
        if self.is_deepspeed_enabled:
            if self.accelerator.state.deepspeed_plugin.zero_stage == 3 and self.precompute_ref_log_probs:
                raise ValueError(
                    "You cannot use `precompute_ref_log_probs=True` with Deepspeed ZeRO-3. Please set `precompute_ref_log_probs=False`."
                )

        if self.ref_model is None:
            if not (self.is_peft_model or self.precompute_ref_log_probs):
                raise ValueError(
                    "No reference model and model is not a Peft model. Try setting `precompute_ref_log_probs=True`"
                )
        else:
            if self.is_deepspeed_enabled:
                self.ref_model = prepare_deepspeed(self.ref_model, self.accelerator)
            else:
                self.ref_model = self.accelerator.prepare_model(self.ref_model, evaluation_mode=True)

        # Import Liger loss if enabled
        if self.args.use_liger_loss:
            if not is_liger_kernel_available():
                raise ImportError(
                    "You set `use_liger_loss=True` but the liger kernel is not available. "
                    "Please install liger-kernel first: `pip install liger-kernel`"
                )
            if self.loss_type in ["apo_zero_unpaired"]:
                raise ValueError(
                    "You cannot set `loss_type='apo_zero_unpaired'` with liger-kernel."
                    "Only KTO loss is supported with liger-kernel."
                )
            if self.precompute_ref_log_probs:
                raise ValueError(
                    "You cannot use `precompute_ref_log_probs=True` with liger kernel. Please set "
                    "`precompute_ref_log_probs=False`."
                )
            if self.is_peft_model or self.ref_adapter_name is not None:
                raise ValueError(
                    "You cannot use `use_liger_loss=True` with Peft models. Please set `use_liger_loss=False`."
                )
            self.kto_loss_fn = LigerFusedLinearKTOLoss(
                ignore_index=self.label_pad_token_id, beta=self.beta, use_ref_model=(self.ref_model is not None)
            )

    @contextmanager
    def null_ref_context(self):
        """Context manager for handling null reference model (that is, peft adapter manipulation)."""
        with (
            self.accelerator.unwrap_model(self.model).disable_adapter()
            if self.is_peft_model and not self.ref_adapter_name
            else nullcontext()
        ):
            if self.ref_adapter_name:
                self.model.set_adapter(self.ref_adapter_name)
            yield
            if self.ref_adapter_name:
                self.model.set_adapter(self.model_adapter_name or "default")

    def get_train_dataloader(self) -> DataLoader:
        """
        Returns the training [`~torch.utils.data.DataLoader`].

        Subclass of transformers.src.transformers.trainer.get_train_dataloader to precompute `ref_log_probs`.
        """

        if self.precompute_ref_log_probs and not self._precomputed_train_ref_log_probs:
            dataloader_params = {
                "batch_size": self.args.per_device_train_batch_size,
                "collate_fn": self.data_collator,
                "num_workers": self.args.dataloader_num_workers,
                "pin_memory": self.args.dataloader_pin_memory,
                "shuffle": False,
            }

            # prepare dataloader
            data_loader = self.accelerator.prepare(DataLoader(self.train_dataset, **dataloader_params))
            reference_completion_logps = []
            reference_KL_logps = []

            for padded_batch in tqdm(iterable=data_loader, desc="Train dataset reference log probs"):
                reference_completion_logp, reference_KL_logp = self.compute_reference_log_probs(padded_batch)

                reference_completion_logp = self.accelerator.gather_for_metrics(reference_completion_logp)
                reference_completion_logps.append(reference_completion_logp.cpu())

                if self.calculate_KL:
                    reference_KL_logp = self.accelerator.gather_for_metrics(reference_KL_logp)
                    reference_KL_logps.append(reference_KL_logp.cpu())

            self.train_dataset = self.train_dataset.add_column(
                name="reference_logps", column=torch.cat(reference_completion_logps).float().numpy()
            )

            if self.calculate_KL:
                self.train_dataset = self.train_dataset.add_column(
                    name="reference_KL_logps", column=torch.cat(reference_KL_logps).float().numpy()
                )

            self._precomputed_train_ref_log_probs = True

        return super().get_train_dataloader()

    def get_eval_dataloader(self, eval_dataset: Optional[Dataset] = None) -> DataLoader:
        """
        Returns the evaluation [`~torch.utils.data.DataLoader`].

        Subclass of transformers.src.transformers.trainer.get_eval_dataloader to precompute `ref_log_probs`.

        Args:
            eval_dataset (`torch.utils.data.Dataset`, *optional*):
                If provided, will override `self.eval_dataset`. If it is a [`~datasets.Dataset`], columns not accepted
                by the `model.forward()` method are automatically removed. It must implement `__len__`.
        """
        if eval_dataset is None and self.eval_dataset is None:
            raise ValueError("Trainer: evaluation requires an eval_dataset.")
        eval_dataset = eval_dataset if eval_dataset is not None else self.eval_dataset

        if self.precompute_ref_log_probs and not self._precomputed_eval_ref_log_probs:
            dataloader_params = {
                "batch_size": self.args.per_device_eval_batch_size,
                "collate_fn": self.data_collator,
                "num_workers": self.args.dataloader_num_workers,
                "pin_memory": self.args.dataloader_pin_memory,
                "shuffle": False,
            }

            # prepare dataloader
            data_loader = self.accelerator.prepare(DataLoader(eval_dataset, **dataloader_params))

            reference_completion_logps = []
            reference_KL_logps = []

            for padded_batch in tqdm(iterable=data_loader, desc="Eval dataset reference log probs"):
                reference_completion_logp, reference_KL_logp = self.compute_reference_log_probs(padded_batch)

                reference_completion_logp = self.accelerator.gather_for_metrics(reference_completion_logp)
                reference_completion_logps.append(reference_completion_logp.cpu())

                if self.calculate_KL:
                    reference_KL_logp = self.accelerator.gather_for_metrics(reference_KL_logp)
                    reference_KL_logps.append(reference_KL_logp.cpu())

            eval_dataset = eval_dataset.add_column(
                name="reference_logps", column=torch.cat(reference_completion_logps).float().numpy()
            )
            if self.calculate_KL:
                eval_dataset = eval_dataset.add_column(
                    name="reference_KL_logps", column=torch.cat(reference_KL_logps).float().numpy()
                )

            # Save calculated reference_chosen_logps and reference_rejected_logps to the eval_dataset for subsequent runs
            if self.eval_dataset is not None:
                self.eval_dataset = eval_dataset
            self._precomputed_eval_ref_log_probs = True

        return super().get_eval_dataloader(eval_dataset=eval_dataset)

    def compute_reference_log_probs(self, padded_batch: dict) -> dict:
        """Computes log probabilities of the reference model for a single padded batch of a KTO specific dataset."""
        with torch.no_grad():
            if self.ref_model is None:
                with self.null_ref_context():
                    if self.is_encoder_decoder:
                        completion_logits = self.model(
                            padded_batch["prompt_input_ids"],
                            attention_mask=padded_batch["prompt_attention_mask"],
                            decoder_input_ids=padded_batch.get("completion_decoder_input_ids"),
                            labels=padded_batch["completion_labels"],
                        ).logits

                        if self.calculate_KL:
                            KL_logits = self.model(
                                padded_batch["KL_prompt_input_ids"],
                                attention_mask=padded_batch["KL_prompt_attention_mask"],
                                decoder_input_ids=padded_batch.get("KL_completion_decoder_input_ids"),
                                labels=padded_batch["KL_completion_labels"],
                            ).logits
                    else:
                        completion_logits = self.model(
                            padded_batch["completion_input_ids"],
                            attention_mask=padded_batch["completion_attention_mask"],
                        ).logits

                        if self.calculate_KL:
                            KL_logits = self.model(
                                padded_batch["KL_completion_input_ids"],
                                attention_mask=padded_batch["KL_completion_attention_mask"],
                            ).logits
            else:
                if self.is_encoder_decoder:
                    completion_logits = self.ref_model(
                        padded_batch["prompt_input_ids"],
                        attention_mask=padded_batch["prompt_attention_mask"],
                        decoder_input_ids=padded_batch.get("completion_decoder_input_ids"),
                        labels=padded_batch["completion_labels"],
                    ).logits

                    if self.calculate_KL:
                        KL_logits = self.ref_model(
                            padded_batch["KL_prompt_input_ids"],
                            attention_mask=padded_batch["KL_prompt_attention_mask"],
                            decoder_input_ids=padded_batch.get("KL_completion_decoder_input_ids"),
                            labels=padded_batch["KL_completion_labels"],
                        ).logits
                else:
                    completion_logits = self.ref_model(
                        padded_batch["completion_input_ids"], attention_mask=padded_batch["completion_attention_mask"]
                    ).logits

                    if self.calculate_KL:
                        KL_logits = self.ref_model(
                            padded_batch["KL_completion_input_ids"],
                            attention_mask=padded_batch["KL_completion_attention_mask"],
                        ).logits

        completion_logps = self.get_batch_logps(
            completion_logits,
            padded_batch["completion_labels"],
            average_log_prob=False,
            is_encoder_decoder=self.is_encoder_decoder,
            label_pad_token_id=self.label_pad_token_id,
        )

        if self.calculate_KL:
            KL_logps = self.get_batch_logps(
                KL_logits,
                padded_batch["KL_completion_labels"],
                average_log_prob=False,
                is_encoder_decoder=self.is_encoder_decoder,
                label_pad_token_id=self.label_pad_token_id,
            )
        else:
            KL_logps = None

        return completion_logps, KL_logps

    @staticmethod
    def get_batch_logps(
        logits: torch.FloatTensor,
        labels: torch.LongTensor,
        average_log_prob: bool = False,
        label_pad_token_id: int = -100,
        is_encoder_decoder: bool = False,
    ) -> torch.FloatTensor:
        """Compute the log probabilities of the given labels under the given logits.

        Args:
            logits: Logits of the model (unnormalized). Shape: (batch_size, sequence_length, vocab_size)
            labels: Labels for which to compute the log probabilities. Label tokens with a value of label_pad_token_id are ignored. Shape: (batch_size, sequence_length)
            average_log_prob: If True, return the average log probability per (non-masked) token. Otherwise, return the sum of the log probabilities of the (non-masked) tokens.

        Returns:
            A tensor of shape (batch_size,) containing the average/sum log probabilities of the given labels under the given logits.
        """
        if logits.shape[:-1] != labels.shape:
            raise ValueError("Logits (batch and sequence length dim) and labels must have the same shape.")

        if not is_encoder_decoder:
            labels = labels[:, 1:].clone()
            logits = logits[:, :-1, :]
        else:
            # Fixes end-dec RuntimeError
            labels = labels.clone()

        loss_mask = labels != label_pad_token_id

        # dummy token; we'll ignore the losses on these tokens later
        labels[labels == label_pad_token_id] = 0

        per_token_logps = selective_log_softmax(logits, labels)

        if average_log_prob:
            return (per_token_logps * loss_mask).sum(-1) / loss_mask.sum(-1)
        else:
            return (per_token_logps * loss_mask).sum(-1)

    def forward(
        self, model: nn.Module, batch: dict[str, Union[list, torch.LongTensor]]
    ) -> tuple[torch.FloatTensor, torch.FloatTensor, torch.FloatTensor, torch.FloatTensor]:
        KL_logps = self._compute_kl_logps(model, batch)

        model_kwargs = (
            {
                "labels": batch["completion_labels"],
                "decoder_input_ids": batch.get("completion_decoder_input_ids"),
            }
            if self.is_encoder_decoder
            else {}
        )
        if self.aux_loss_enabled:
            model_kwargs["output_router_logits"] = True

        outputs = model(
            batch["completion_input_ids"],
            attention_mask=batch["completion_attention_mask"],
            **model_kwargs,
        )
        completion_logits = outputs.logits

        completion_logps = self.get_batch_logps(
            completion_logits,
            batch["completion_labels"],
            average_log_prob=False,
            is_encoder_decoder=self.is_encoder_decoder,
            label_pad_token_id=self.label_pad_token_id,
        )

        if completion_logps.shape[0] != len(batch["label"]):
            raise ValueError(
                "There is a mismatch between the number of examples in this batch and the number of "
                "examples for which an output sequence was predicted."
            )

        chosen_idx = [i for i in range(completion_logps.shape[0]) if batch["label"][i] is True]
        rejected_idx = [i for i in range(completion_logps.shape[0]) if batch["label"][i] is False]

        chosen_logps = completion_logps[chosen_idx, ...]
        rejected_logps = completion_logps[rejected_idx, ...]

        chosen_logits = completion_logits[chosen_idx, ...]
        rejected_logits = completion_logits[rejected_idx, ...]

        if self.aux_loss_enabled:
            return (chosen_logps, rejected_logps, chosen_logits, rejected_logits, KL_logps, outputs.aux_loss)
        else:
            return (chosen_logps, rejected_logps, chosen_logits, rejected_logits, KL_logps)

    def kto_loss(
        self,
        policy_chosen_logps: torch.FloatTensor,
        policy_rejected_logps: torch.FloatTensor,
        policy_KL_logps: torch.FloatTensor,
        reference_chosen_logps: torch.FloatTensor,
        reference_rejected_logps: torch.FloatTensor,
        reference_KL_logps: torch.FloatTensor,
    ) -> tuple[torch.FloatTensor, torch.FloatTensor, torch.FloatTensor, torch.FloatTensor]:
        """Compute the KTO loss for a batch of policy and reference model log probabilities.

        Args:
            policy_chosen_logps: Log probabilities of the policy model for the chosen responses. Shape: (num(chosen) in batch_size,)
            policy_rejected_logps: Log probabilities of the policy model for the rejected responses. Shape: (num(rejected) in batch_size,)
            policy_KL_logps: Log probabilities of the policy model for the KL responses. Shape: (batch_size,)
            reference_chosen_logps: Log probabilities of the reference model for the chosen responses. Shape: (num(chosen) in batch_size,)
            reference_rejected_logps: Log probabilities of the reference model for the rejected responses. Shape: (num(rejected) in batch_size,)
            reference_KL_logps: Log probabilities of the reference model for the KL responses. Shape: (batch_size,)

        Returns:
            A tuple of four tensors: (losses, chosen_rewards, rejected_rewards, KL).
            The losses tensor contains the KTO loss for each example in the batch.
            The chosen_rewards and rejected_rewards tensors contain the rewards for the chosen and rejected responses, respectively.
            The KL tensor contains the detached KL divergence estimate between the policy and reference models.
        """
        if self.calculate_KL:
            kl = (policy_KL_logps - reference_KL_logps).mean().detach()
            kl = self.accelerator.gather_for_metrics(kl).mean().clamp(min=0)
        else:
            kl = torch.zeros(1).to(policy_chosen_logps.device)

        # Chosen losses
        if policy_chosen_logps.shape[0] != 0 or reference_chosen_logps.shape[0] != 0:
            chosen_logratios = policy_chosen_logps - reference_chosen_logps

            if self.loss_type == "kto":
                # Eqn (7) of the KTO paper (https://huggingface.co/papers/2402.01306)
                chosen_losses = 1 - F.sigmoid(self.beta * (chosen_logratios - kl))
            elif self.loss_type == "apo_zero_unpaired":
                # Unpaired variant of Eqn (7) of the APO paper (https://huggingface.co/papers/2408.06266)
                # Use this loss when you believe the chosen outputs are better than your model's default output
                chosen_losses = 1 - F.sigmoid(self.beta * chosen_logratios)

            chosen_rewards = self.beta * chosen_logratios.detach()

        else:
            # lists can't be empty -- if they are, then accelerate.gather will hang
            chosen_losses = torch.Tensor([]).to(self.accelerator.device)
            chosen_rewards = torch.Tensor([]).to(self.accelerator.device)

        # Rejected losses
        if policy_rejected_logps.shape[0] != 0 or reference_rejected_logps.shape[0] != 0:
            rejected_logratios = policy_rejected_logps - reference_rejected_logps

            if self.loss_type == "kto":
                rejected_losses = 1 - F.sigmoid(self.beta * (kl - rejected_logratios))
            elif self.loss_type == "apo_zero_unpaired":
                rejected_losses = F.sigmoid(self.beta * rejected_logratios)

            rejected_rewards = self.beta * rejected_logratios.detach()
        else:
            # lists can't be empty -- if they are, then accelerate.gather will hang
            rejected_losses = torch.Tensor([]).to(self.accelerator.device)
            rejected_rewards = torch.Tensor([]).to(self.accelerator.device)

        losses = torch.cat(
            (self.desirable_weight * chosen_losses, self.undesirable_weight * rejected_losses),
            0,
        )

        return losses, chosen_rewards, rejected_rewards, kl

    def _compute_kl_logps(self, model, batch):
        """Compute KL log probabilities for a given batch."""
        KL_logps = None
        if self.calculate_KL:
            if self.is_encoder_decoder:
                KL_model_kwargs = {
                    "input_ids": batch["KL_prompt_input_ids"],
                    "attention_mask": batch["KL_prompt_attention_mask"],
                    "labels": batch["KL_completion_labels"],
                    "decoder_input_ids": batch.get("KL_completion_decoder_input_ids"),
                }
            else:
                KL_model_kwargs = {
                    "input_ids": batch["KL_completion_input_ids"],
                    "attention_mask": batch["KL_completion_attention_mask"],
                }

            with torch.no_grad():
                KL_logits = model(**KL_model_kwargs).logits

            KL_logps = self.get_batch_logps(
                KL_logits,
                batch["KL_completion_labels"],
                average_log_prob=False,
                is_encoder_decoder=self.is_encoder_decoder,
                label_pad_token_id=self.label_pad_token_id,
            )
        return KL_logps

    def _compute_loss_liger(self, model, batch):
        """
        Compute the KTO loss using the Liger-Kernel's LigerFusedLinearKTOLoss.

        Args:
            model: The policy model used for generating log probabilities and outputs. It could be an encoder-decoder model or a regular language model.
            batch: A dictionary containing the input data and labels for the batch.

        Returns:
            A dictionary containing the following keys:
                - "loss": The computed KTO loss for the batch.
                - "chosen_logits_sum": Sum of the logits for the chosen responses from the policy model.
                - "rejected_logits_sum": Sum of the logits for the rejected responses from the policy model.
                - "chosen_logps": Log probabilities of the chosen responses from the policy model.
                - "rejected_logps": Log probabilities of the rejected responses from the policy model.
                - "chosen_rewards": Rewards for the chosen responses.
                - "rejected_rewards": Rewards for the rejected responses.
                - "kl": The KL divergence between the policy and reference models (detached).

            If auxiliary loss is enabled, the dictionary will also include:
                - "aux_loss": The auxiliary loss from the model outputs.
        """
        policy_KL_logps = self._compute_kl_logps(model, batch)
        reference_KL_logps = self._compute_kl_logps(self.ref_model, batch)
        if self.calculate_KL:
            kl = (policy_KL_logps - reference_KL_logps).mean().detach()
            kl = self.accelerator.gather_for_metrics(kl).mean().clamp(min=0)
        else:
            kl = torch.zeros(1).to(self.accelerator.device)

        model_kwargs = (
            {
                "labels": batch["completion_labels"],
                "decoder_input_ids": batch.get("completion_decoder_input_ids"),
            }
            if self.is_encoder_decoder
            else {}
        )
        if self.aux_loss_enabled:
            model_kwargs["output_router_logits"] = True

        if self.is_encoder_decoder:
            # 1. Get encoder outputs
            encoder_outputs = model.get_encoder()(
                batch["completion_input_ids"],
                attention_mask=batch["completion_attention_mask"],
                return_dict=True,
                **model_kwargs,
            )
            # 2. Get decoder outputs
            outputs = model.get_decoder()(
                input_ids=model_kwargs["decoder_input_ids"],
                encoder_hidden_states=encoder_outputs.last_hidden_state,
                use_cache=False,
                **model_kwargs,
            )
            # 1. Get reference encoder outputs
            ref_encoder_outputs = self.ref_model.get_encoder()(
                batch["completion_input_ids"],
                attention_mask=batch["completion_attention_mask"],
                return_dict=True,
                **model_kwargs,
            )
            # 2. Get reference decoder outputs
            ref_outputs = self.ref_model.get_decoder()(
                input_ids=model_kwargs["decoder_input_ids"],
                encoder_hidden_states=ref_encoder_outputs.last_hidden_state,
                use_cache=False,
                **model_kwargs,
            )
        else:
            # skip the lm head and get the last hidden state
            if hasattr(model, "get_decoder"):
                base_model = model.get_decoder()
            else:
                base_model = getattr(model, self.args.base_model_attribute_name)
            outputs = base_model(
                batch["completion_input_ids"],
                attention_mask=batch["completion_attention_mask"],
                use_cache=False,
                **model_kwargs,
            )

            # reference model
            if hasattr(self.ref_model, "get_decoder"):
                ref_base_model = self.ref_model.get_decoder()
            else:
                ref_base_model = getattr(self.ref_model, self.args.base_model_attribute_name)
            ref_outputs = ref_base_model(
                batch["completion_input_ids"],
                attention_mask=batch["completion_attention_mask"],
                use_cache=False,
                **model_kwargs,
            )
        lm_head = model.get_output_embeddings()
        ref_lm_head = self.ref_model.get_output_embeddings()

        (
            loss,
            (
                chosen_logps_sum,
                rejected_logps_sum,
                chosen_logits_sum,
                rejected_logits_sum,
                chosen_rewards_sum,
                rejected_rewards_sum,
            ),
        ) = self.kto_loss_fn(
            _input=outputs.last_hidden_state[:, :-1] if not self.is_encoder_decoder else outputs.last_hidden_state,
            lin_weight=lm_head.weight,
            target=batch["completion_labels"][:, 1:],
            bias=lm_head.bias if hasattr(lm_head, "bias") else None,
            preference_labels=torch.tensor(batch["label"], dtype=torch.bool).to(self.accelerator.device),
            ref_input=ref_outputs.last_hidden_state[:, :-1]
            if not self.is_encoder_decoder
            else outputs.last_hidden_state,
            ref_weight=ref_lm_head.weight,
            ref_bias=ref_lm_head.bias if hasattr(lm_head, "bias") else None,
            kl=kl,
        )

        output = {
            "loss": loss,
            "chosen_logits_sum": chosen_logits_sum,
            "rejected_logits_sum": rejected_logits_sum,
            "chosen_logps_sum": chosen_logps_sum,
            "rejected_logps_sum": rejected_logps_sum,
            "chosen_rewards_sum": chosen_rewards_sum,
            "rejected_rewards_sum": rejected_rewards_sum,
            "kl": kl,
        }
        if self.aux_loss_enabled:
            output["aux_loss"] = outputs.aux_loss

        return output

    def get_batch_loss_metrics(
        self,
        model,
        batch: dict[str, Union[list, torch.LongTensor]],
    ):
        """Compute the KTO loss and other metrics for the given batch of inputs for train or test."""
        metrics = {}
        batch = {k: (v.to(self.accelerator.device) if isinstance(v, torch.Tensor) else v) for k, v in batch.items()}

        labels = torch.tensor(batch["label"])
        num_chosen = labels.sum().to(self.accelerator.device)
        num_rejected = (len(labels) - num_chosen).to(self.accelerator.device)

        if self.args.use_liger_loss:
            model_output = self._compute_loss_liger(model, batch)
            losses = model_output["loss"]
            policy_chosen_logits = model_output["chosen_logits_sum"]
            policy_rejected_logits = model_output["rejected_logits_sum"]
            policy_chosen_logps = model_output["chosen_logps_sum"]
            policy_rejected_logps = model_output["rejected_logps_sum"]
            chosen_rewards = model_output["chosen_rewards_sum"]
            rejected_rewards = model_output["rejected_rewards_sum"]
            kl = model_output["kl"]
            if self.aux_loss_enabled:
                aux_loss = model_output["aux_loss"]
        else:
            forward_output = self.forward(model, batch)
            (
                policy_chosen_logps,
                policy_rejected_logps,
                policy_chosen_logits,
                policy_rejected_logits,
                policy_KL_logps,
            ) = forward_output[:5]
            if self.aux_loss_enabled:
                aux_loss = forward_output[5]

            # if reference_logps in batch use them, otherwise use the reference model
            if "reference_logps" in batch:
                chosen_idx = [i for i in range(batch["reference_logps"].shape[0]) if batch["label"][i] is True]
                rejected_idx = [i for i in range(batch["reference_logps"].shape[0]) if batch["label"][i] is False]

                reference_chosen_logps = batch["reference_logps"][chosen_idx, ...]
                reference_rejected_logps = batch["reference_logps"][rejected_idx, ...]
                if self.calculate_KL:
                    reference_KL_logps = batch["reference_KL_logps"]
                else:
                    reference_KL_logps = None
            else:
                with torch.no_grad():
                    if self.ref_model is None:
                        with self.null_ref_context():
                            (
                                reference_chosen_logps,
                                reference_rejected_logps,
                                _,
                                _,
                                reference_KL_logps,
                            ) = self.forward(self.model, batch)[:5]
                    else:
                        (
                            reference_chosen_logps,
                            reference_rejected_logps,
                            _,
                            _,
                            reference_KL_logps,
                        ) = self.forward(self.ref_model, batch)[:5]

            losses, chosen_rewards, rejected_rewards, kl = self.kto_loss(
                policy_chosen_logps,
                policy_rejected_logps,
                policy_KL_logps,
                reference_chosen_logps,
                reference_rejected_logps,
                reference_KL_logps,
            )

        metrics["kl"] = kl.item()

        all_num_chosen = self.accelerator.gather_for_metrics(num_chosen).sum().item()
        all_num_rejected = self.accelerator.gather_for_metrics(num_rejected).sum().item()

        if all_num_chosen > 0:
            metrics["rewards/chosen_sum"] = (
                self.accelerator.gather_for_metrics(chosen_rewards.nansum()).nansum().item()
            )
            metrics["logps/chosen_sum"] = (
                self.accelerator.gather_for_metrics(policy_chosen_logps.nansum()).nansum().item()
            )
            metrics["logits/chosen_sum"] = (
                self.accelerator.gather_for_metrics(policy_chosen_logits.nansum()).nansum().item()
            )
            metrics["count/chosen"] = all_num_chosen

        if all_num_rejected > 0:
            metrics["rewards/rejected_sum"] = (
                self.accelerator.gather_for_metrics(rejected_rewards.nansum()).nansum().item()
            )
            metrics["logps/rejected_sum"] = (
                self.accelerator.gather_for_metrics(policy_rejected_logps.nansum()).nansum().item()
            )
            metrics["logits/rejected_sum"] = (
                self.accelerator.gather_for_metrics(policy_rejected_logits.nansum()).nansum().item()
            )
            metrics["count/rejected"] = all_num_rejected

        loss = losses.nanmean()
        if self.aux_loss_enabled:
            loss += self.aux_loss_coef * aux_loss

        return loss, metrics

    def compute_loss(
        self,
        model: Union[PreTrainedModel, nn.Module],
        inputs: dict[str, Union[torch.Tensor, Any]],
        return_outputs=False,
        num_items_in_batch=None,
    ) -> Union[torch.Tensor, tuple[torch.Tensor, dict[str, torch.Tensor]]]:
        compute_loss_context_manager = (
            autocast(self.accelerator.device.type) if self._peft_has_been_casted_to_bf16 else nullcontext()
        )

        with compute_loss_context_manager:
            loss, metrics = self.get_batch_loss_metrics(model, inputs)

        # Make sure to move the loss to the device the original accumulating loss is at back in the `Trainer` class:
        loss = loss.to(self.args.device)
        # force log the metrics
        if self.accelerator.is_main_process:
            self.store_metrics(metrics, train_eval="train")

        if return_outputs:
            return (loss, metrics)
        return loss

    def store_metrics(self, metrics: dict[str, float], train_eval: Literal["train", "eval"] = "train") -> None:
        for key, value in metrics.items():
            self._stored_metrics[train_eval][key].append(value)

    def _get_train_sampler(self, dataset: Optional[Dataset] = None) -> Optional[torch.utils.data.Sampler]:
        if dataset is None:
            dataset = self.train_dataset
        if dataset is None or not has_length(dataset):
            return None
        return SequentialSampler(dataset)

    def generate_from_model_and_ref(self, model, batch: dict[str, torch.LongTensor]) -> tuple[str, str]:
        """Generate samples from the model and reference model for the given batch of inputs."""

        # If one uses `generate_during_eval` with peft + bf16, we need to explicitly call generate with
        # the torch amp context manager as some hidden states are silently casted to full precision.
        generate_context_manager = (
            autocast(self.accelerator.device.type) if self._peft_has_been_casted_to_bf16 else nullcontext()
        )

        with generate_context_manager:
            policy_output = model.generate(
                input_ids=batch["prompt_input_ids"],
                attention_mask=batch["prompt_attention_mask"],
                max_length=self.max_length,
                do_sample=True,
                pad_token_id=self.processing_class.pad_token_id,
            )

            # if reference_output in batch use that otherwise use the reference model
            if "reference_output" in batch:
                reference_output = batch["reference_output"]
            else:
                if self.ref_model is None:
                    with self.null_ref_context():
                        reference_output = self.model.generate(
                            input_ids=batch["prompt_input_ids"],
                            attention_mask=batch["prompt_attention_mask"],
                            max_length=self.max_length,
                            do_sample=True,
                            pad_token_id=self.processing_class.pad_token_id,
                        )
                else:
                    reference_output = self.ref_model.generate(
                        input_ids=batch["prompt_input_ids"],
                        attention_mask=batch["prompt_attention_mask"],
                        max_length=self.max_length,
                        do_sample=True,
                        pad_token_id=self.processing_class.pad_token_id,
                    )

        policy_output = pad_to_length(policy_output, self.max_length, self.processing_class.pad_token_id)
        policy_output_decoded = self.processing_class.batch_decode(policy_output, skip_special_tokens=True)

        reference_output = pad_to_length(reference_output, self.max_length, self.processing_class.pad_token_id)
        reference_output_decoded = self.processing_class.batch_decode(reference_output, skip_special_tokens=True)

        return policy_output_decoded, reference_output_decoded

    def prediction_step(
        self,
        model: Union[PreTrainedModel, nn.Module],
        inputs: dict[str, Union[torch.Tensor, Any]],
        prediction_loss_only: bool,
        ignore_keys: Optional[list[str]] = None,
    ):
        if ignore_keys is None:
            if hasattr(model, "config"):
                ignore_keys = getattr(model.config, "keys_to_ignore_at_inference", [])
            else:
                ignore_keys = []

        prediction_context_manager = (
            autocast(self.accelerator.device.type) if self._peft_has_been_casted_to_bf16 else nullcontext()
        )
        with torch.no_grad(), prediction_context_manager:
            loss, metrics = self.get_batch_loss_metrics(model, inputs)

        # force log the metrics
        if self.accelerator.is_main_process:
            self.store_metrics(metrics, train_eval="eval")

        if prediction_loss_only:
            return (loss.detach(), None, None)

        # logits for the chosen and rejected samples from model
        logits_dict = {}
        if "logits/chosen_sum" in metrics:
            logits_dict["eval_logits/chosen"] = metrics["logits/chosen_sum"]
        if "logits/rejected_sum" in metrics:
            logits_dict["eval_logits/rejected"] = metrics["logits/rejected_sum"]
        logits = [v for k, v in logits_dict.items() if k not in ignore_keys]
        logits = torch.tensor(logits, device=self.accelerator.device)
        labels = torch.zeros(logits.shape[0], device=self.accelerator.device)

        return (loss.detach(), logits, labels)

    def evaluation_loop(
        self,
        dataloader: DataLoader,
        description: str,
        prediction_loss_only: Optional[bool] = None,
        ignore_keys: Optional[list[str]] = None,
        metric_key_prefix: str = "eval",
    ) -> EvalLoopOutput:
        """
        Overriding built-in evaluation loop to store metrics for each batch.
        Prediction/evaluation loop, shared by `Trainer.evaluate()` and `Trainer.predict()`.

        Works both with or without labels.
        """

        # Sample and save to game log if requested (for one batch to save time)
        if self.generate_during_eval:
            # Generate random indices within the range of the total number of samples
            num_samples = len(dataloader.dataset)
            random_indices = random.sample(range(num_samples), k=self.args.eval_batch_size)

            # Use dataloader.dataset.select to get the random batch without iterating over the DataLoader
            random_batch_dataset = dataloader.dataset.select(random_indices)
            random_batch = self.data_collator(random_batch_dataset)
            random_batch = self._prepare_inputs(random_batch)

            target_indicies = [i for i in range(len(random_batch["label"])) if random_batch["label"][i] is False]
            target_batch = {
                "prompt_input_ids": random_batch["prompt_input_ids"][target_indicies],
                "prompt_attention_mask": random_batch["prompt_attention_mask"][target_indicies],
                "prompt": itemgetter(*target_indicies)(random_batch["prompt"]),
            }
            policy_output_decoded, ref_output_decoded = self.generate_from_model_and_ref(self.model, target_batch)

            table = pd.DataFrame(
                columns=["Prompt", "Policy", "Ref Model"],
                data=[
                    [prompt, pol[len(prompt) :], ref[len(prompt) :]]
                    for prompt, pol, ref in zip(target_batch["prompt"], policy_output_decoded, ref_output_decoded)
                ],
            )
            if "wandb" in self.args.report_to:
                wandb.log({"game_log": wandb.Table(data=table)})

            if "comet_ml" in self.args.report_to:
                log_table_to_comet_experiment(
                    name="game_log.csv",
                    table=table,
                )

        # Base evaluation
        initial_output = super().evaluation_loop(
            dataloader, description, prediction_loss_only, ignore_keys, metric_key_prefix
        )

        return initial_output

    def log(self, logs: dict[str, float], start_time: Optional[float] = None) -> None:
        """
        Log `logs` on the various objects watching training, including stored metrics.

        Args:
            logs (`dict[str, float]`):
                The values to log.
            start_time (`float` or `None`, *optional*, defaults to `None`):
                Start time of the training.
        """
        # logs either has 'loss' or 'eval_loss'
        train_eval = "train" if "loss" in logs else "eval"
        # train metrics should have no prefix, eval should have 'eval_'
        prefix = "eval_" if train_eval == "eval" else ""
        # accumulate average metrics from sums and lengths
        for split in ["chosen", "rejected"]:
            if f"count/{split}" in self._stored_metrics[train_eval]:
                count_sum = torch.Tensor(self._stored_metrics[train_eval][f"count/{split}"]).sum().item()
                for metric in ["rewards", "logps", "logits"]:
                    logs[f"{prefix}{metric}/{split}"] = (
                        torch.Tensor(self._stored_metrics[train_eval][f"{metric}/{split}_sum"]).sum().item()
                        / count_sum
                    )
                    # delete obsolete metric
                    del self._stored_metrics[train_eval][f"{metric}/{split}_sum"]
                del self._stored_metrics[train_eval][f"count/{split}"]
        # calculate reward margin
        if f"{prefix}rewards/chosen" in logs and f"{prefix}rewards/rejected" in logs:
            logs[f"{prefix}rewards/margins"] = logs[f"{prefix}rewards/chosen"] - logs[f"{prefix}rewards/rejected"]
        # Add averaged stored metrics to logs
        for key, metrics in self._stored_metrics[train_eval].items():
            logs[f"{prefix}{key}"] = torch.Tensor(metrics).mean().item()
        del self._stored_metrics[train_eval]
        return super().log(logs, start_time)

    # Ensure the model card is saved along with the checkpoint
    def _save_checkpoint(self, model, trial):
        if self.args.hub_model_id is None:
            model_name = Path(self.args.output_dir).name
        else:
            model_name = self.args.hub_model_id.split("/")[-1]
        self.create_model_card(model_name=model_name)
        super()._save_checkpoint(model, trial)

    def create_model_card(
        self,
        model_name: Optional[str] = None,
        dataset_name: Optional[str] = None,
        tags: Union[str, list[str], None] = None,
    ):
        """
        Creates a draft of a model card using the information available to the `Trainer`.

        Args:
            model_name (`str` or `None`, *optional*, defaults to `None`):
                Name of the model.
            dataset_name (`str` or `None`, *optional*, defaults to `None`):
                Name of the dataset used for training.
            tags (`str`, `list[str]` or `None`, *optional*, defaults to `None`):
                Tags to be associated with the model card.
        """
        if not self.is_world_process_zero():
            return

        if hasattr(self.model.config, "_name_or_path") and not os.path.isdir(self.model.config._name_or_path):
            base_model = self.model.config._name_or_path
        else:
            base_model = None

        tags = tags or set()
        if isinstance(tags, str):
            tags = {tags}

        if hasattr(self.model.config, "unsloth_version"):
            tags.add("unsloth")

        tags.update(self._tag_names)

        citation = textwrap.dedent("""\
        @article{ethayarajh2024kto,
            title        = {{KTO: Model Alignment as Prospect Theoretic Optimization}},
            author       = {Kawin Ethayarajh and Winnie Xu and Niklas Muennighoff and Dan Jurafsky and Douwe Kiela},
            year         = 2024,
            eprint       = {arXiv:2402.01306},
        }""")

        model_card = generate_model_card(
            base_model=base_model,
            model_name=model_name,
            hub_model_id=self.hub_model_id,
            dataset_name=dataset_name,
            tags=tags,
            wandb_url=wandb.run.get_url() if is_wandb_available() and wandb.run is not None else None,
            comet_url=get_comet_experiment_url(),
            trainer_name="KTO",
            trainer_citation=citation,
            paper_title="KTO: Model Alignment as Prospect Theoretic Optimization",
            paper_id="2402.01306",
        )

        model_card.save(os.path.join(self.args.output_dir, "README.md"))