finetrainers/trainer/sft_trainer/trainer.py

import functools
import json
import math
import os
import time
from pathlib import Path
from typing import TYPE_CHECKING, Any, Dict, Iterable, List, Optional, Union

import datasets.distributed
import diffusers
import torch
import torch.backends
import transformers
import wandb
from diffusers import DiffusionPipeline
from diffusers.hooks import apply_layerwise_casting
from diffusers.training_utils import cast_training_params
from diffusers.utils import export_to_video
from huggingface_hub import create_repo, upload_folder
from peft import LoraConfig, get_peft_model_state_dict
from tqdm import tqdm

from ... import data, logging, optimizer, parallel, patches, utils
from ...config import TrainingType
from ...state import State, TrainState


if TYPE_CHECKING:
    from ...args import BaseArgs
    from ...models import ModelSpecification


logger = logging.get_logger()


class SFTTrainer:
    # fmt: off
    _all_component_names = ["tokenizer", "tokenizer_2", "tokenizer_3", "text_encoder", "text_encoder_2", "text_encoder_3", "transformer", "unet", "vae", "scheduler"]
    _condition_component_names = ["tokenizer", "tokenizer_2", "tokenizer_3", "text_encoder", "text_encoder_2", "text_encoder_3"]
    _latent_component_names = ["vae"]
    _diffusion_component_names = ["transformer", "unet", "scheduler"]
    # fmt: on

    def __init__(self, args: "BaseArgs", model_specification: "ModelSpecification") -> None:
        self.args = args
        self.state = State()
        self.state.train_state = TrainState()

        # Tokenizers
        self.tokenizer = None
        self.tokenizer_2 = None
        self.tokenizer_3 = None

        # Text encoders
        self.text_encoder = None
        self.text_encoder_2 = None
        self.text_encoder_3 = None

        # Denoisers
        self.transformer = None
        self.unet = None

        # Autoencoders
        self.vae = None

        # Scheduler
        self.scheduler = None

        # Optimizer & LR scheduler
        self.optimizer = None
        self.lr_scheduler = None

        # Checkpoint manager
        self.checkpointer = None

        self._init_distributed()
        self._init_config_options()

        # Perform any patches that might be necessary for training to work as expected
        patches.perform_patches_for_training(self.args, self.state.parallel_backend)

        self.model_specification = model_specification
        self._are_condition_models_loaded = False

    def run(self) -> None:
        try:
            self._prepare_models()
            self._prepare_trainable_parameters()
            self._prepare_for_training()
            self._prepare_dataset()
            self._prepare_checkpointing()
            self._train()
            # trainer._evaluate()
        except Exception as e:
            logger.error(f"Error during training: {e}")
            self.state.parallel_backend.destroy()
            raise e

    def _prepare_models(self) -> None:
        logger.info("Initializing models")

        diffusion_components = self.model_specification.load_diffusion_models()
        self._set_components(diffusion_components)

        if self.state.parallel_backend.pipeline_parallel_enabled:
            raise NotImplementedError(
                "Pipeline parallelism is not supported yet. This will be supported in the future."
            )

    def _prepare_trainable_parameters(self) -> None:
        logger.info("Initializing trainable parameters")

        parallel_backend = self.state.parallel_backend

        if self.args.training_type == TrainingType.FULL_FINETUNE:
            logger.info("Finetuning transformer with no additional parameters")
            utils.set_requires_grad([self.transformer], True)
        else:
            logger.info("Finetuning transformer with PEFT parameters")
            utils.set_requires_grad([self.transformer], False)

        # Layerwise upcasting must be applied before adding the LoRA adapter.
        # If we don't perform this before moving to device, we might OOM on the GPU. So, best to do it on
        # CPU for now, before support is added in Diffusers for loading and enabling layerwise upcasting directly.
        if self.args.training_type == "lora" and "transformer" in self.args.layerwise_upcasting_modules:
            apply_layerwise_casting(
                self.transformer,
                storage_dtype=self.args.layerwise_upcasting_storage_dtype,
                compute_dtype=self.args.transformer_dtype,
                skip_modules_pattern=self.args.layerwise_upcasting_skip_modules_pattern,
                non_blocking=True,
            )

        transformer_lora_config = None
        if self.args.training_type == TrainingType.LORA:
            transformer_lora_config = LoraConfig(
                r=self.args.rank,
                lora_alpha=self.args.lora_alpha,
                init_lora_weights=True,
                target_modules=self.args.target_modules,
            )
            self.transformer.add_adapter(transformer_lora_config)

        # # TODO(aryan): it might be nice to add some assertions here to make sure that lora parameters are still in fp32
        # # even if layerwise upcasting. Would be nice to have a test as well
        # self.register_saving_loading_hooks(transformer_lora_config)

        # Make sure the trainable params are in float32 if data sharding is not enabled. For FSDP, we need all
        # parameters to be of the same dtype.
        if parallel_backend.data_sharding_enabled:
            self.transformer.to(dtype=self.args.transformer_dtype)
        else:
            if self.args.training_type == TrainingType.LORA:
                cast_training_params([self.transformer], dtype=torch.float32)

    def _prepare_for_training(self) -> None:
        # 1. Apply parallelism
        parallel_backend = self.state.parallel_backend
        world_mesh = parallel_backend.get_mesh()
        model_specification = self.model_specification

        if parallel_backend.context_parallel_enabled:
            raise NotImplementedError(
                "Context parallelism is not supported yet. This will be supported in the future."
            )

        if parallel_backend.tensor_parallel_enabled:
            # TODO(aryan): handle fp8 from TorchAO here
            model_specification.apply_tensor_parallel(
                backend=parallel.ParallelBackendEnum.PTD,
                device_mesh=parallel_backend.get_mesh()["tp"],
                transformer=self.transformer,
            )

        # Enable gradient checkpointing
        if self.args.gradient_checkpointing:
            # TODO(aryan): support other checkpointing types
            utils.apply_activation_checkpointing(self.transformer, checkpointing_type="full")

        # Enable DDP, FSDP or HSDP
        if parallel_backend.data_sharding_enabled:
            # TODO(aryan): remove this when supported
            if self.args.parallel_backend == "accelerate":
                raise NotImplementedError("Data sharding is not supported with Accelerate yet.")

            if parallel_backend.data_replication_enabled:
                logger.info("Applying HSDP to the model")
            else:
                logger.info("Applying FSDP to the model")

            # Apply FSDP or HSDP
            if parallel_backend.data_replication_enabled or parallel_backend.context_parallel_enabled:
                dp_mesh_names = ("dp_replicate", "dp_shard_cp")
            else:
                dp_mesh_names = ("dp_shard_cp",)

            parallel.apply_fsdp2_ptd(
                model=self.transformer,
                dp_mesh=world_mesh[dp_mesh_names],
                param_dtype=self.args.transformer_dtype,
                reduce_dtype=torch.float32,
                output_dtype=None,
                pp_enabled=parallel_backend.pipeline_parallel_enabled,
                cpu_offload=False,  # TODO(aryan): needs to be tested and allowed for enabling later
            )
        elif parallel_backend.data_replication_enabled:
            logger.info("Applying DDP to the model")

            if world_mesh.ndim > 1:
                raise ValueError("DDP not supported for > 1D parallelism")

            parallel_backend.apply_ddp(self.transformer, world_mesh)

        self._move_components_to_device()

        # 2. Prepare optimizer and lr scheduler
        # For training LoRAs, we can be a little more optimal. Currently, the OptimizerWrapper only accepts torch::nn::Module.
        # This causes us to loop over all the parameters (even ones that don't require gradients, as in LoRA) at each optimizer
        # step. This is OK (see https://github.com/pytorch/pytorch/blob/2f40f789dafeaa62c4e4b90dbf4a900ff6da2ca4/torch/optim/sgd.py#L85-L99)
        # but can be optimized a bit by maybe creating a simple wrapper module encompassing the actual parameters that require
        # gradients. TODO(aryan): look into it in the future.
        model_parts = [self.transformer]
        self.state.num_trainable_parameters = sum(
            p.numel() for m in model_parts for p in m.parameters() if p.requires_grad
        )

        # Setup distributed optimizer and lr scheduler
        logger.info("Initializing optimizer and lr scheduler")
        self.state.train_state = TrainState()
        self.optimizer = optimizer.get_optimizer(
            parallel_backend=self.args.parallel_backend,
            name=self.args.optimizer,
            model_parts=model_parts,
            learning_rate=self.args.lr,
            beta1=self.args.beta1,
            beta2=self.args.beta2,
            beta3=self.args.beta3,
            epsilon=self.args.epsilon,
            weight_decay=self.args.weight_decay,
            fused=False,
        )
        self.lr_scheduler = optimizer.get_lr_scheduler(
            parallel_backend=self.args.parallel_backend,
            name=self.args.lr_scheduler,
            optimizer=self.optimizer,
            num_warmup_steps=self.args.lr_warmup_steps,
            num_training_steps=self.args.train_steps,
            # TODO(aryan): handle last_epoch
        )
        self.optimizer, self.lr_scheduler = parallel_backend.prepare_optimizer(self.optimizer, self.lr_scheduler)

        # 3. Initialize trackers, directories and repositories
        self._init_logging()
        self._init_trackers()
        self._init_directories_and_repositories()

    def _prepare_dataset(self) -> None:
        logger.info("Initializing dataset and dataloader")

        with open(self.args.dataset_config, "r") as file:
            dataset_configs = json.load(file)["datasets"]
        logger.info(f"Training configured to use {len(dataset_configs)} datasets")

        datasets = []
        for config in dataset_configs:
            data_root = config.pop("data_root", None)
            dataset_file = config.pop("dataset_file", None)
            dataset_type = config.pop("dataset_type")
            caption_options = config.pop("caption_options", {})

            if data_root is not None and dataset_file is not None:
                raise ValueError("Both data_root and dataset_file cannot be provided in the same dataset config.")

            dataset_name_or_root = data_root or dataset_file
            dataset = data.initialize_dataset(
                dataset_name_or_root, dataset_type, streaming=True, infinite=True, _caption_options=caption_options
            )

            if not dataset._precomputable_once and self.args.precomputation_once:
                raise ValueError(
                    f"Dataset {dataset_name_or_root} does not support precomputing all embeddings at once."
                )

            logger.info(f"Initialized dataset: {dataset_name_or_root}")
            dataset = self.state.parallel_backend.prepare_dataset(dataset)
            dataset = data.wrap_iterable_dataset_for_preprocessing(dataset, dataset_type, config)
            datasets.append(dataset)

        dataset = data.combine_datasets(datasets, buffer_size=self.args.dataset_shuffle_buffer_size, shuffle=True)
        dataloader = self.state.parallel_backend.prepare_dataloader(
            dataset, batch_size=1, num_workers=self.args.dataloader_num_workers, pin_memory=self.args.pin_memory
        )

        self.dataset = dataset
        self.dataloader = dataloader

    def _prepare_checkpointing(self) -> None:
        parallel_backend = self.state.parallel_backend

        def save_model_hook(state_dict: Dict[str, Any]) -> None:
            if parallel_backend.is_main_process:
                if self.args.training_type == TrainingType.LORA:
                    state_dict = get_peft_model_state_dict(self.transformer, state_dict)
                    self.model_specification._save_lora_weights(self.args.output_dir, state_dict, self.scheduler)
                elif self.args.training_type == TrainingType.FULL_FINETUNE:
                    self.model_specification._save_model(
                        self.args.output_dir, self.transformer, state_dict, self.scheduler
                    )
            parallel_backend.wait_for_everyone()

        enable_state_checkpointing = self.args.checkpointing_steps > 0
        self.checkpointer = utils.PTDCheckpointManager(
            dataloader=self.dataloader,
            model_parts=[self.transformer],
            optimizers=self.optimizer,
            schedulers=self.lr_scheduler,
            states={"train_state": self.state.train_state},
            checkpointing_steps=self.args.checkpointing_steps,
            checkpointing_limit=self.args.checkpointing_limit,
            output_dir=self.args.output_dir,
            enable=enable_state_checkpointing,
            _callback_fn=save_model_hook,
        )

        resume_from_checkpoint = self.args.resume_from_checkpoint
        if resume_from_checkpoint == "latest":
            resume_from_checkpoint = -1
        if resume_from_checkpoint is not None:
            self.checkpointer.load(resume_from_checkpoint)

    def _train(self) -> None:
        logger.info("Starting training")

        parallel_backend = self.state.parallel_backend
        train_state = self.state.train_state
        device = parallel_backend.device

        memory_statistics = utils.get_memory_statistics()
        logger.info(f"Memory before training start: {json.dumps(memory_statistics, indent=4)}")

        global_batch_size = self.args.batch_size * parallel_backend._dp_degree
        info = {
            "trainable parameters": self.state.num_trainable_parameters,
            "train steps": self.args.train_steps,
            "per-replica batch size": self.args.batch_size,
            "global batch size": global_batch_size,
            "gradient accumulation steps": self.args.gradient_accumulation_steps,
        }
        logger.info(f"Training configuration: {json.dumps(info, indent=4)}")

        progress_bar = tqdm(
            range(0, self.args.train_steps),
            initial=train_state.step,
            desc="Training steps",
            disable=not parallel_backend.is_local_main_process,
        )

        generator = torch.Generator(device=device)
        if self.args.seed is not None:
            generator = generator.manual_seed(self.args.seed)
        self.state.generator = generator

        patch_size = 1
        if (
            getattr(self.transformer.config, "patch_size", None) is not None
            and getattr(self.transformer.config, "patch_size_t", None) is not None
        ):
            patch_size = self.transformer.config.patch_size * self.transformer.config.patch_size_t
        elif isinstance(getattr(self.transformer.config, "patch_size", None), int):
            patch_size = self.transformer.config.patch_size
        elif isinstance(getattr(self.transformer.config, "patch_size", None), (list, tuple)):
            patch_size = math.prod(self.transformer.config.patch_size)

        scheduler_sigmas = utils.get_scheduler_sigmas(self.scheduler)
        scheduler_sigmas = (
            scheduler_sigmas.to(device=device, dtype=torch.float32) if scheduler_sigmas is not None else None
        )
        scheduler_alphas = utils.get_scheduler_alphas(self.scheduler)
        scheduler_alphas = (
            scheduler_alphas.to(device=device, dtype=torch.float32) if scheduler_alphas is not None else None
        )
        timesteps_buffer = []

        self.transformer.train()
        data_iterator = iter(self.dataloader)

        preprocessor = data.initialize_preprocessor(
            rank=parallel_backend.rank,
            num_items=self.args.precomputation_items if self.args.enable_precomputation else 1,
            processor_fn={
                "condition": self.model_specification.prepare_conditions,
                "latent": functools.partial(
                    self.model_specification.prepare_latents, compute_posterior=not self.args.precomputation_once
                ),
            },
            save_dir=self.args.precomputation_dir,
            enable_precomputation=self.args.enable_precomputation,
        )
        precomputed_condition_iterator: Iterable[Dict[str, Any]] = None
        precomputed_latent_iterator: Iterable[Dict[str, Any]] = None
        sampler = data.ResolutionSampler(
            batch_size=self.args.batch_size, dim_keys=self.model_specification._resolution_dim_keys
        )
        requires_gradient_step = True
        accumulated_loss = 0.0

        while (
            train_state.step < self.args.train_steps and train_state.observed_data_samples < self.args.max_data_samples
        ):
            # 1. Load & preprocess data if required
            if preprocessor.requires_data:
                # TODO(aryan): We should do the following here:
                # - Force checkpoint the trainable models, optimizers, schedulers and train state
                # - Do the precomputation
                # - Load the checkpointed models, optimizers, schedulers and train state back, and continue training
                # This way we can be more memory efficient again, since the latest rewrite of precomputation removed
                # this logic.
                precomputed_condition_iterator, precomputed_latent_iterator = self._prepare_data(
                    preprocessor, data_iterator
                )

            # 2. Prepare batch
            try:
                condition_item = next(precomputed_condition_iterator)
                latent_item = next(precomputed_latent_iterator)
                sampler.consume(condition_item, latent_item)
            except StopIteration:
                if requires_gradient_step:
                    self.optimizer.step()
                    self.lr_scheduler.step()
                    requires_gradient_step = False
                logger.info("Data exhausted. Exiting training loop.")
                break

            if sampler.is_ready:
                condition_batch, latent_batch = sampler.get_batch()
                condition_model_conditions = self.model_specification.collate_conditions(condition_batch)
                latent_model_conditions = self.model_specification.collate_latents(latent_batch)
            else:
                continue

            train_state.step += 1
            train_state.observed_data_samples += self.args.batch_size * parallel_backend._dp_degree

            lmc_latents = latent_model_conditions["latents"]
            train_state.observed_num_tokens += math.prod(lmc_latents.shape[:-1]) // patch_size

            logger.debug(f"Starting training step ({train_state.step}/{self.args.train_steps})")

            utils.align_device_and_dtype(latent_model_conditions, device, self.args.transformer_dtype)
            utils.align_device_and_dtype(condition_model_conditions, device, self.args.transformer_dtype)
            latent_model_conditions = utils.make_contiguous(latent_model_conditions)
            condition_model_conditions = utils.make_contiguous(condition_model_conditions)

            # 3. Forward pass
            sigmas = utils.prepare_sigmas(
                scheduler=self.scheduler,
                sigmas=scheduler_sigmas,
                batch_size=self.args.batch_size,
                num_train_timesteps=self.scheduler.config.num_train_timesteps,
                flow_weighting_scheme=self.args.flow_weighting_scheme,
                flow_logit_mean=self.args.flow_logit_mean,
                flow_logit_std=self.args.flow_logit_std,
                flow_mode_scale=self.args.flow_mode_scale,
                device=device,
                generator=self.state.generator,
            )
            sigmas = utils.expand_tensor_dims(sigmas, latent_model_conditions["latents"].ndim)

            pred, target, sigmas = self.model_specification.forward(
                transformer=self.transformer,
                scheduler=self.scheduler,
                condition_model_conditions=condition_model_conditions,
                latent_model_conditions=latent_model_conditions,
                sigmas=sigmas,
                compute_posterior=not self.args.precomputation_once,
            )

            timesteps = (sigmas * 1000.0).long()
            weights = utils.prepare_loss_weights(
                scheduler=self.scheduler,
                alphas=scheduler_alphas[timesteps] if scheduler_alphas is not None else None,
                sigmas=sigmas,
                flow_weighting_scheme=self.args.flow_weighting_scheme,
            )
            weights = utils.expand_tensor_dims(weights, pred.ndim)

            # 4. Compute loss & backward pass
            loss = weights.float() * (pred.float() - target.float()).pow(2)
            # Average loss across all but batch dimension
            loss = loss.mean(list(range(1, loss.ndim)))
            # Average loss across batch dimension
            loss = loss.mean()
            if self.args.gradient_accumulation_steps > 1:
                loss = loss / self.args.gradient_accumulation_steps
            loss.backward()
            accumulated_loss += loss.detach().item()
            requires_gradient_step = True

            # 5. Clip gradients
            model_parts = [self.transformer]
            grad_norm = utils.torch._clip_grad_norm_while_handling_failing_dtensor_cases(
                [p for m in model_parts for p in m.parameters()],
                self.args.max_grad_norm,
                foreach=True,
                pp_mesh=parallel_backend.get_mesh("pp") if parallel_backend.pipeline_parallel_enabled else None,
            )

            # 6. Step optimizer & log metrics
            logs = {}

            if train_state.step % self.args.gradient_accumulation_steps == 0:
                # TODO(aryan): revisit no_sync() for FSDP
                self.optimizer.step()
                self.lr_scheduler.step()
                self.optimizer.zero_grad()

                if grad_norm is not None:
                    logs["grad_norm"] = grad_norm if isinstance(grad_norm, float) else grad_norm.detach().item()
                if (
                    parallel_backend.data_replication_enabled
                    or parallel_backend.data_sharding_enabled
                    or parallel_backend.context_parallel_enabled
                ):
                    dp_cp_mesh = parallel_backend.get_mesh("dp_cp")
                    global_avg_loss, global_max_loss = (
                        parallel.dist_mean(torch.tensor([accumulated_loss], device=device), dp_cp_mesh),
                        parallel.dist_max(torch.tensor([accumulated_loss], device=device), dp_cp_mesh),
                    )
                else:
                    global_avg_loss = global_max_loss = accumulated_loss

                logs["global_avg_loss"] = global_avg_loss
                logs["global_max_loss"] = global_max_loss
                train_state.global_avg_losses.append(global_avg_loss)
                train_state.global_max_losses.append(global_max_loss)
                accumulated_loss = 0.0
                requires_gradient_step = False

            progress_bar.update(1)
            progress_bar.set_postfix(logs)

            timesteps_buffer.extend([(train_state.step, t) for t in timesteps.detach().cpu().numpy().tolist()])

            if train_state.step % self.args.logging_steps == 0:
                # TODO(aryan): handle non-SchedulerWrapper schedulers (probably not required eventually) since they might not be dicts
                # TODO(aryan): causes NCCL hang for some reason. look into later
                # logs.update(self.lr_scheduler.get_last_lr())

                # timesteps_table = wandb.Table(data=timesteps_buffer, columns=["step", "timesteps"])
                # logs["timesteps"] = wandb.plot.scatter(
                #     timesteps_table, "step", "timesteps", title="Timesteps distribution"
                # )
                timesteps_buffer = []

                logs["observed_data_samples"] = train_state.observed_data_samples
                logs["observed_num_tokens"] = train_state.observed_num_tokens

                parallel_backend.log(logs, step=train_state.step)
                train_state.log_steps.append(train_state.step)

            # 7. Save checkpoint if required
            self.checkpointer.save(
                step=train_state.step, _device=device, _is_main_process=parallel_backend.is_main_process
            )

            # 8. Perform validation if required
            if train_state.step % self.args.validation_steps == 0:
                self._validate(step=train_state.step, final_validation=False)

        # 9. Final checkpoint, validation & cleanup
        self.checkpointer.save(
            train_state.step, force=True, _device=device, _is_main_process=parallel_backend.is_main_process
        )
        parallel_backend.wait_for_everyone()
        self._validate(step=train_state.step, final_validation=True)

        self._delete_components()
        memory_statistics = utils.get_memory_statistics()
        logger.info(f"Memory after training end: {json.dumps(memory_statistics, indent=4)}")

        # 10. Upload artifacts to hub
        if parallel_backend.is_main_process and self.args.push_to_hub:
            upload_folder(
                repo_id=self.state.repo_id,
                folder_path=self.args.output_dir,
                ignore_patterns=[f"{self.checkpointer._prefix}_*"],
            )

        parallel_backend.destroy()

    def _validate(self, step: int, final_validation: bool = False) -> None:
        if self.args.validation_dataset_file is None:
            return

        logger.info("Starting validation")

        # 1. Load validation dataset
        parallel_backend = self.state.parallel_backend
        dp_mesh = parallel_backend.get_mesh("dp_replicate")

        if dp_mesh is not None:
            local_rank, dp_world_size = dp_mesh.get_local_rank(), dp_mesh.size()
        else:
            local_rank, dp_world_size = 0, 1

        dataset = data.ValidationDataset(self.args.validation_dataset_file)
        dataset._data = datasets.distributed.split_dataset_by_node(dataset._data, local_rank, dp_world_size)
        validation_dataloader = data.DPDataLoader(
            local_rank,
            dataset,
            batch_size=1,
            num_workers=self.args.dataloader_num_workers,
            collate_fn=lambda items: items,
        )
        data_iterator = iter(validation_dataloader)
        main_process_prompts_to_filenames = {}  # Used to save model card
        all_processes_artifacts = []  # Used to gather artifacts from all processes

        memory_statistics = utils.get_memory_statistics()
        logger.info(f"Memory before validation start: {json.dumps(memory_statistics, indent=4)}")

        seed = self.args.seed if self.args.seed is not None else 0
        generator = torch.Generator(device=parallel_backend.device).manual_seed(seed)
        pipeline = self._init_pipeline(final_validation=final_validation)

        # 2. Run validation
        # TODO(aryan): when running validation with FSDP, if the number of data points is not divisible by dp_shards, we
        # will hang indefinitely. Either pad the dataset or raise an error early on during initialization if the dataset
        # size is not divisible by dp_shards.
        self.transformer.eval()
        while True:
            validation_data = next(data_iterator, None)
            if validation_data is None:
                break

            logger.debug(
                f"Validating {validation_data=} on rank={parallel_backend.rank}.", local_main_process_only=False
            )

            validation_data = validation_data[0]
            validation_artifacts = self.model_specification.validation(
                pipeline=pipeline, generator=generator, **validation_data
            )

            PROMPT = validation_data["prompt"]
            IMAGE = validation_data.get("image", None)
            VIDEO = validation_data.get("video", None)
            EXPORT_FPS = validation_data.get("export_fps", 30)

            # 2.1. If there are any initial images or videos, they will be logged to keep track of them as
            # conditioning for generation.
            prompt_filename = utils.string_to_filename(PROMPT)[:25]
            artifacts = {
                "input_image": data.ImageArtifact(value=IMAGE),
                "input_video": data.VideoArtifact(value=VIDEO),
            }

            # 2.2. Track the artifacts generated from validation
            for i, validation_artifact in enumerate(validation_artifacts):
                if validation_artifact.value is None:
                    continue
                artifacts.update({f"artifact_{i}": validation_artifact})

            # 2.3. Save the artifacts to the output directory and create appropriate logging objects
            # TODO(aryan): Currently, we only support WandB so we've hardcoded it here. Needs to be revisited.
            for index, (key, artifact) in enumerate(list(artifacts.items())):
                assert isinstance(artifact, (data.ImageArtifact, data.VideoArtifact))

                time_, rank, ext = int(time.time()), parallel_backend.rank, artifact.file_extension
                filename = "validation-" if not final_validation else "final-"
                filename += f"{step}-{rank}-{index}-{prompt_filename}-{time_}.{ext}"
                output_filename = os.path.join(self.args.output_dir, filename)

                if parallel_backend.is_main_process and artifact.file_extension == "mp4":
                    main_process_prompts_to_filenames[PROMPT] = filename

                if artifact.type == "image" and artifact.value is not None:
                    logger.debug(
                        f"Saving image from rank={parallel_backend.rank} to {output_filename}",
                        local_main_process_only=False,
                    )
                    artifact.value.save(output_filename)
                    all_processes_artifacts.append(wandb.Image(output_filename, caption=PROMPT))
                elif artifact.type == "video" and artifact.value is not None:
                    logger.debug(
                        f"Saving video from rank={parallel_backend.rank} to {output_filename}",
                        local_main_process_only=False,
                    )
                    export_to_video(artifact.value, output_filename, fps=EXPORT_FPS)
                    all_processes_artifacts.append(wandb.Video(output_filename, caption=PROMPT))

        # 3. Cleanup & log artifacts
        parallel_backend.wait_for_everyone()

        # Remove all hooks that might have been added during pipeline initialization to the models
        pipeline.remove_all_hooks()
        del pipeline

        utils.free_memory()
        memory_statistics = utils.get_memory_statistics()
        logger.info(f"Memory after validation end: {json.dumps(memory_statistics, indent=4)}")
        torch.cuda.reset_peak_memory_stats(parallel_backend.device)

        # Gather artifacts from all processes. We also need to flatten them since each process returns a list of artifacts.
        # TODO(aryan): probably should only all gather from dp mesh process group
        all_artifacts = [None] * parallel_backend.world_size
        torch.distributed.all_gather_object(all_artifacts, all_processes_artifacts)
        all_artifacts = [artifact for artifacts in all_artifacts for artifact in artifacts]

        if parallel_backend.is_main_process:
            tracker_key = "final" if final_validation else "validation"
            artifact_log_dict = {}

            image_artifacts = [artifact for artifact in all_artifacts if isinstance(artifact, wandb.Image)]
            if len(image_artifacts) > 0:
                artifact_log_dict["images"] = image_artifacts
            video_artifacts = [artifact for artifact in all_artifacts if isinstance(artifact, wandb.Video)]
            if len(video_artifacts) > 0:
                artifact_log_dict["videos"] = video_artifacts
            parallel_backend.log({tracker_key: artifact_log_dict}, step=step)

            if self.args.push_to_hub and final_validation:
                video_filenames = list(main_process_prompts_to_filenames.values())
                prompts = list(main_process_prompts_to_filenames.keys())
                utils.save_model_card(
                    args=self.args, repo_id=self.state.repo_id, videos=video_filenames, validation_prompts=prompts
                )

        parallel_backend.wait_for_everyone()
        if not final_validation:
            self.transformer.train()

    def _evaluate(self) -> None:
        raise NotImplementedError("Evaluation has not been implemented yet.")

    def _init_distributed(self) -> None:
        # TODO: Accelerate disables native_amp for MPS. Probably need to do the same with implementation.
        world_size = int(os.environ["WORLD_SIZE"])

        # TODO(aryan): handle other backends
        backend_cls: parallel.ParallelBackendType = parallel.get_parallel_backend_cls(self.args.parallel_backend)
        self.state.parallel_backend = backend_cls(
            world_size=world_size,
            pp_degree=self.args.pp_degree,
            dp_degree=self.args.dp_degree,
            dp_shards=self.args.dp_shards,
            cp_degree=self.args.cp_degree,
            tp_degree=self.args.tp_degree,
            backend="nccl",
            timeout=self.args.init_timeout,
            logging_dir=self.args.logging_dir,
            output_dir=self.args.output_dir,
            gradient_accumulation_steps=self.args.gradient_accumulation_steps,
        )

        if self.args.seed is not None:
            world_mesh = self.state.parallel_backend.get_mesh()
            utils.enable_determinism(self.args.seed, world_mesh)

    def _init_logging(self) -> None:
        transformers_log_level = transformers.utils.logging.set_verbosity_error
        diffusers_log_level = diffusers.utils.logging.set_verbosity_error

        if self.args.verbose == 0:
            if self.state.parallel_backend.is_local_main_process:
                transformers_log_level = transformers.utils.logging.set_verbosity_warning
                diffusers_log_level = diffusers.utils.logging.set_verbosity_warning
        elif self.args.verbose == 1:
            if self.state.parallel_backend.is_local_main_process:
                transformers_log_level = transformers.utils.logging.set_verbosity_info
                diffusers_log_level = diffusers.utils.logging.set_verbosity_info
        elif self.args.verbose == 2:
            if self.state.parallel_backend.is_local_main_process:
                transformers_log_level = transformers.utils.logging.set_verbosity_debug
                diffusers_log_level = diffusers.utils.logging.set_verbosity_debug
        else:
            transformers_log_level = transformers.utils.logging.set_verbosity_debug
            diffusers_log_level = diffusers.utils.logging.set_verbosity_debug

        transformers_log_level()
        diffusers_log_level()

        logging._set_parallel_backend(self.state.parallel_backend)
        logger.info("Initialized FineTrainers")

    def _init_trackers(self) -> None:
        # TODO(aryan): handle multiple trackers
        trackers = ["wandb"]
        experiment_name = self.args.tracker_name or "finetrainers-experiment"
        self.state.parallel_backend.initialize_trackers(
            trackers, experiment_name=experiment_name, config=self._get_training_info(), log_dir=self.args.logging_dir
        )

    def _init_directories_and_repositories(self) -> None:
        if self.state.parallel_backend.is_main_process:
            self.args.output_dir = Path(self.args.output_dir)
            self.args.output_dir.mkdir(parents=True, exist_ok=True)
            self.state.output_dir = Path(self.args.output_dir)

            if self.args.push_to_hub:
                repo_id = self.args.hub_model_id or Path(self.args.output_dir).name
                self.state.repo_id = create_repo(token=self.args.hub_token, repo_id=repo_id, exist_ok=True).repo_id

    def _init_config_options(self) -> None:
        # Enable TF32 for faster training on Ampere GPUs: https://pytorch.org/docs/stable/notes/cuda.html#tensorfloat-32-tf32-on-ampere-devices
        if self.args.allow_tf32 and torch.cuda.is_available():
            torch.backends.cuda.matmul.allow_tf32 = True

    def _move_components_to_device(
        self, components: Optional[List[torch.nn.Module]] = None, device: Optional[Union[str, torch.device]] = None
    ) -> None:
        if device is None:
            device = self.state.parallel_backend.device
        if components is None:
            components = [self.text_encoder, self.text_encoder_2, self.text_encoder_3, self.transformer, self.vae]
        components = utils.get_non_null_items(components)
        components = list(filter(lambda x: hasattr(x, "to"), components))
        for component in components:
            component.to(device)

    def _set_components(self, components: Dict[str, Any]) -> None:
        for component_name in self._all_component_names:
            existing_component = getattr(self, component_name, None)
            new_component = components.get(component_name, existing_component)
            setattr(self, component_name, new_component)

    def _delete_components(self, component_names: Optional[List[str]] = None) -> None:
        if component_names is None:
            component_names = self._all_component_names
        for component_name in component_names:
            setattr(self, component_name, None)
        utils.free_memory()
        utils.synchronize_device()

    def _init_pipeline(self, final_validation: bool = False) -> DiffusionPipeline:
        parallel_backend = self.state.parallel_backend
        module_names = ["text_encoder", "text_encoder_2", "text_encoder_3", "transformer", "vae"]

        if not final_validation:
            module_names.remove("transformer")
            pipeline = self.model_specification.load_pipeline(
                tokenizer=self.tokenizer,
                tokenizer_2=self.tokenizer_2,
                tokenizer_3=self.tokenizer_3,
                text_encoder=self.text_encoder,
                text_encoder_2=self.text_encoder_2,
                text_encoder_3=self.text_encoder_3,
                # TODO(aryan): handle unwrapping for compiled modules
                # transformer=utils.unwrap_model(accelerator, self.transformer),
                transformer=self.transformer,
                vae=self.vae,
                enable_slicing=self.args.enable_slicing,
                enable_tiling=self.args.enable_tiling,
                enable_model_cpu_offload=self.args.enable_model_cpu_offload,
                training=True,
            )
        else:
            self._delete_components()

            # Load the transformer weights from the final checkpoint if performing full-finetune
            transformer = None
            if self.args.training_type == TrainingType.FULL_FINETUNE:
                transformer = self.model_specification.load_diffusion_models()["transformer"]

            pipeline = self.model_specification.load_pipeline(
                transformer=transformer,
                enable_slicing=self.args.enable_slicing,
                enable_tiling=self.args.enable_tiling,
                enable_model_cpu_offload=self.args.enable_model_cpu_offload,
                training=False,
                device=parallel_backend.device,
            )

            # Load the LoRA weights if performing LoRA finetuning
            if self.args.training_type == TrainingType.LORA:
                pipeline.load_lora_weights(self.args.output_dir)

        components = {module_name: getattr(pipeline, module_name, None) for module_name in module_names}
        self._set_components(components)
        self._move_components_to_device(list(components.values()))
        return pipeline

    def _prepare_data(
        self,
        preprocessor: Union[data.InMemoryDistributedDataPreprocessor, data.PrecomputedDistributedDataPreprocessor],
        data_iterator,
    ):
        if not self.args.enable_precomputation:
            if not self._are_condition_models_loaded:
                logger.info(
                    "Precomputation disabled. Loading in-memory data loaders. All components will be loaded on GPUs."
                )
                condition_components = self.model_specification.load_condition_models()
                latent_components = self.model_specification.load_latent_models()
                all_components = {**condition_components, **latent_components}
                self._set_components(all_components)
                self._move_components_to_device(list(all_components.values()))
                utils._enable_vae_memory_optimizations(self.vae, self.args.enable_slicing, self.args.enable_tiling)
            else:
                condition_components = {k: v for k in self._condition_component_names if (v := getattr(self, k, None))}
                latent_components = {k: v for k in self._latent_component_names if (v := getattr(self, k, None))}

            condition_iterator = preprocessor.consume(
                "condition",
                components=condition_components,
                data_iterator=data_iterator,
                generator=self.state.generator,
                cache_samples=True,
            )
            latent_iterator = preprocessor.consume(
                "latent",
                components=latent_components,
                data_iterator=data_iterator,
                generator=self.state.generator,
                use_cached_samples=True,
                drop_samples=True,
            )

            self._are_condition_models_loaded = True
        else:
            logger.info("Precomputed condition & latent data exhausted. Loading & preprocessing new data.")

            # TODO(aryan): This needs to be revisited. For some reason, the tests did not detect that self.transformer
            # had become None after this but should have been loaded back from the checkpoint.
            # parallel_backend = self.state.parallel_backend
            # train_state = self.state.train_state
            # self.checkpointer.save(
            #     train_state.step,
            #     force=True,
            #     _device=parallel_backend.device,
            #     _is_main_process=parallel_backend.is_main_process,
            # )
            # self._delete_components(component_names=["transformer", "unet"])

            if self.args.precomputation_once:
                consume_fn = preprocessor.consume_once
            else:
                consume_fn = preprocessor.consume

            # Prepare condition iterators
            condition_components = self.model_specification.load_condition_models()
            component_names = list(condition_components.keys())
            component_modules = list(condition_components.values())
            self._set_components(condition_components)
            self._move_components_to_device(component_modules)
            condition_iterator = consume_fn(
                "condition",
                components=condition_components,
                data_iterator=data_iterator,
                generator=self.state.generator,
                cache_samples=True,
            )
            self._delete_components(component_names)
            del condition_components, component_names, component_modules

            # Prepare latent iterators
            latent_components = self.model_specification.load_latent_models()
            utils._enable_vae_memory_optimizations(self.vae, self.args.enable_slicing, self.args.enable_tiling)
            component_names = list(latent_components.keys())
            component_modules = list(latent_components.values())
            self._set_components(latent_components)
            self._move_components_to_device(component_modules)
            latent_iterator = consume_fn(
                "latent",
                components=latent_components,
                data_iterator=data_iterator,
                generator=self.state.generator,
                use_cached_samples=True,
                drop_samples=True,
            )
            self._delete_components(component_names)
            del latent_components, component_names, component_modules

            # self.checkpointer.load()
            # self.transformer = self.checkpointer.states["model"].model[0]

        return condition_iterator, latent_iterator

    def _get_training_info(self) -> Dict[str, Any]:
        info = self.args.to_dict()

        # Removing flow matching arguments when not using flow-matching objective
        diffusion_args = info.get("diffusion_arguments", {})
        scheduler_name = self.scheduler.__class__.__name__ if self.scheduler is not None else ""
        if scheduler_name != "FlowMatchEulerDiscreteScheduler":
            filtered_diffusion_args = {k: v for k, v in diffusion_args.items() if "flow" not in k}
        else:
            filtered_diffusion_args = diffusion_args

        info.update({"diffusion_arguments": filtered_diffusion_args})
        return info