Create load_model.py

load_model.py

@@ -0,0 +1,936 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+import ast
+import collections
+import contextlib
+import inspect
+import logging
+import os
+import re
+import time
+import traceback
+from collections import OrderedDict
+from pathlib import Path
+from typing import Any, Dict, Optional, Union
+
+import numpy as np
+import torch
+from fairseq.data import data_utils
+from fairseq.dataclass.configs import CheckpointConfig
+from fairseq.dataclass.utils import (
+    convert_namespace_to_omegaconf,
+    overwrite_args_by_name,
+)
+from fairseq.distributed.fully_sharded_data_parallel import FSDP, has_FSDP
+from fairseq.file_io import PathManager
+from fairseq.models import FairseqDecoder, FairseqEncoder
+from omegaconf import DictConfig, OmegaConf, open_dict
+
+logger = logging.getLogger(__name__)
+
+
+def save_checkpoint(cfg: CheckpointConfig, trainer, epoch_itr, val_loss):
+    from fairseq import meters
+
+    # only one worker should attempt to create the required dir
+    if trainer.data_parallel_rank == 0:
+        os.makedirs(cfg.save_dir, exist_ok=True)
+
+    prev_best = getattr(save_checkpoint, "best", val_loss)
+    if val_loss is not None:
+        best_function = max if cfg.maximize_best_checkpoint_metric else min
+        save_checkpoint.best = best_function(val_loss, prev_best)
+
+    if cfg.no_save:
+        return None
+
+    trainer.consolidate_optimizer()  # TODO(SS): do we need this if no_save_optimizer_state
+
+    if not trainer.should_save_checkpoint_on_current_rank:
+        if trainer.always_call_state_dict_during_save_checkpoint:
+            trainer.state_dict()
+        return None
+
+    write_timer = meters.StopwatchMeter()
+    write_timer.start()
+
+    epoch = epoch_itr.epoch
+    end_of_epoch = epoch_itr.end_of_epoch()
+    updates = trainer.get_num_updates()
+
+    logger.info(f"Preparing to save checkpoint for epoch {epoch} @ {updates} updates")
+
+    def is_better(a, b):
+        return a >= b if cfg.maximize_best_checkpoint_metric else a <= b
+
+    suffix = trainer.checkpoint_suffix
+    checkpoint_conds = collections.OrderedDict()
+    checkpoint_conds["checkpoint{}{}.pt".format(epoch, suffix)] = (
+        end_of_epoch and not cfg.no_epoch_checkpoints and epoch % cfg.save_interval == 0
+    )
+    checkpoint_conds["checkpoint_{}_{}{}.pt".format(epoch, updates, suffix)] = (
+        not end_of_epoch
+        and cfg.save_interval_updates > 0
+        and updates % cfg.save_interval_updates == 0
+    )
+    checkpoint_conds["checkpoint_best{}.pt".format(suffix)] = val_loss is not None and (
+        not hasattr(save_checkpoint, "best")
+        or is_better(val_loss, save_checkpoint.best)
+    )
+    if val_loss is not None and cfg.keep_best_checkpoints > 0:
+        worst_best = getattr(save_checkpoint, "best", None)
+        chkpts = checkpoint_paths(
+            cfg.save_dir,
+            pattern=r"checkpoint\.best_{}_(\d+\.?\d*){}\.pt".format(
+                cfg.best_checkpoint_metric, suffix
+            ),
+        )
+        if len(chkpts) > 0:
+            p = chkpts[-1] if cfg.maximize_best_checkpoint_metric else chkpts[0]
+            worst_best = float(p.rsplit("_")[-1].replace("{}.pt".format(suffix), ""))
+        # add random digits to resolve ties
+        with data_utils.numpy_seed(epoch, updates, val_loss):
+            rand_sfx = np.random.randint(0, cfg.keep_best_checkpoints)
+
+        checkpoint_conds[
+            "checkpoint.best_{}_{:.3f}{}{}.pt".format(
+                cfg.best_checkpoint_metric, val_loss, rand_sfx, suffix
+            )
+        ] = worst_best is None or is_better(val_loss, worst_best)
+    checkpoint_conds[
+        "checkpoint_last{}.pt".format(suffix)
+    ] = not cfg.no_last_checkpoints
+
+    extra_state = {
+        "train_iterator": epoch_itr.state_dict(),
+        "val_loss": val_loss,
+    }
+
+    # Going forward, different tasks could expose an API like this to dump all
+    # the checkpoint worthy attributes in a dictionary which then will be
+    # merged with the parent dictionary to create the "extra_state". This
+    # allows for an extensible yet simple design to checkpoint task level
+    # attributes
+    if hasattr(trainer.task, "get_checkpoint_dict"):
+        extra_state = {**extra_state, **trainer.task.get_checkpoint_dict()}
+        logger.info(f"State of {trainer.task.__class__.__name__} is ready to be persisted with the checkpoint")
+
+    if hasattr(save_checkpoint, "best"):
+        extra_state.update({"best": save_checkpoint.best})
+
+    checkpoints = [
+        os.path.join(cfg.save_dir, fn) for fn, cond in checkpoint_conds.items() if cond
+    ]
+    saved_cp = None
+    if len(checkpoints) > 0 and trainer.should_save_checkpoint_on_current_rank:
+        saved_cp = trainer.save_checkpoint(checkpoints[0], extra_state)
+        for cp in checkpoints[1:]:
+            if cfg.write_checkpoints_asynchronously:
+                # TODO[ioPath]: Need to implement a delayed asynchronous
+                # file copying/moving feature.
+                logger.warning(
+                    f"ioPath is not copying {checkpoints[0]} to {cp} "
+                    "since async write mode is on."
+                )
+            else:
+                assert PathManager.copy(
+                    checkpoints[0], cp, overwrite=True
+                ), f"Failed to copy {checkpoints[0]} to {cp}"
+
+        write_timer.stop()
+        logger.info(
+            "Saved checkpoint {} (epoch {} @ {} updates, score {}) (writing took {} seconds)".format(
+                checkpoints[0], epoch, updates, val_loss, write_timer.sum
+            )
+        )
+
+    if (
+        not end_of_epoch
+        and cfg.keep_interval_updates > 0
+        and trainer.should_save_checkpoint_on_current_rank
+    ):
+        # remove old checkpoints; checkpoints are sorted in descending order
+        if cfg.keep_interval_updates_pattern == -1:
+            checkpoints = checkpoint_paths(
+                cfg.save_dir, pattern=r"checkpoint_\d+_(\d+){}\.pt".format(suffix)
+            )
+        else:
+            checkpoints = checkpoint_paths(
+                cfg.save_dir,
+                pattern=r"checkpoint_\d+_(\d+){}\.pt".format(suffix),
+                keep_match=True,
+            )
+            checkpoints = [
+                x[0]
+                for x in checkpoints
+                if x[1] % cfg.keep_interval_updates_pattern != 0
+            ]
+
+        for old_chk in checkpoints[cfg.keep_interval_updates :]:
+            if os.path.lexists(old_chk):
+                os.remove(old_chk)
+            elif PathManager.exists(old_chk):
+                PathManager.rm(old_chk)
+
+    if cfg.keep_last_epochs > 0 and trainer.should_save_checkpoint_on_current_rank:
+        # remove old epoch checkpoints; checkpoints are sorted in descending order
+        checkpoints = checkpoint_paths(
+            cfg.save_dir, pattern=r"checkpoint(\d+){}\.pt".format(suffix)
+        )
+        for old_chk in checkpoints[cfg.keep_last_epochs :]:
+            if os.path.lexists(old_chk):
+                os.remove(old_chk)
+            elif PathManager.exists(old_chk):
+                PathManager.rm(old_chk)
+
+    if cfg.keep_best_checkpoints > 0 and trainer.should_save_checkpoint_on_current_rank:
+        # only keep the best N checkpoints according to validation metric
+        checkpoints = checkpoint_paths(
+            cfg.save_dir,
+            pattern=r"checkpoint\.best_{}_(\d+\.?\d*){}\.pt".format(
+                cfg.best_checkpoint_metric, suffix
+            ),
+        )
+        if not cfg.maximize_best_checkpoint_metric:
+            checkpoints = checkpoints[::-1]
+        for old_chk in checkpoints[cfg.keep_best_checkpoints :]:
+            if os.path.lexists(old_chk):
+                os.remove(old_chk)
+            elif PathManager.exists(old_chk):
+                PathManager.rm(old_chk)
+
+    return saved_cp
+
+
+def load_checkpoint(cfg: CheckpointConfig, trainer, **passthrough_args):
+    """
+    Load a checkpoint and restore the training iterator.
+
+    *passthrough_args* will be passed through to
+    ``trainer.get_train_iterator``.
+    """
+
+    reset_optimizer = cfg.reset_optimizer
+    reset_lr_scheduler = cfg.reset_lr_scheduler
+    optimizer_overrides = ast.literal_eval(cfg.optimizer_overrides)
+    reset_meters = cfg.reset_meters
+    reset_dataloader = cfg.reset_dataloader
+
+    if cfg.finetune_from_model is not None and (
+        reset_optimizer or reset_lr_scheduler or reset_meters or reset_dataloader
+    ):
+        raise ValueError(
+            "--finetune-from-model can not be set together with either --reset-optimizer"
+            " or reset_lr_scheduler or reset_meters or reset_dataloader"
+        )
+
+    suffix = trainer.checkpoint_suffix
+    if (
+        cfg.restore_file == "checkpoint_last.pt"
+    ):  # default value of restore_file is 'checkpoint_last.pt'
+        checkpoint_path = os.path.join(
+            cfg.save_dir, "checkpoint_last{}.pt".format(suffix)
+        )
+        first_launch = not PathManager.exists(checkpoint_path)
+        if first_launch and getattr(cfg, "continue_once", None) is not None:
+            checkpoint_path = cfg.continue_once
+        elif cfg.finetune_from_model is not None and first_launch:
+            # if there is no last checkpoint to restore, start the finetune from pretrained model
+            # else just use usual logic to load checkpoint, e.g. restart from last checkpoint and etc.
+            if PathManager.exists(cfg.finetune_from_model):
+                checkpoint_path = cfg.finetune_from_model
+                reset_optimizer = True
+                reset_lr_scheduler = True
+                reset_meters = True
+                reset_dataloader = True
+                logger.info(
+                    f"loading pretrained model from {checkpoint_path}: "
+                    "optimizer, lr scheduler, meters, dataloader will be reset"
+                )
+            else:
+                raise ValueError(
+                    f"--finetune-from-model {cfg.finetune_from_model} does not exist"
+                )
+    elif suffix is not None:
+        checkpoint_path = cfg.restore_file.replace(".pt", suffix + ".pt")
+    else:
+        checkpoint_path = cfg.restore_file
+
+    if cfg.restore_file != "checkpoint_last.pt" and cfg.finetune_from_model:
+        raise ValueError(
+            "--finetune-from-model and --restore-file (non-default value) "
+            "can not be specified together: " + str(cfg)
+        )
+
+    extra_state = trainer.load_checkpoint(
+        checkpoint_path,
+        reset_optimizer,
+        reset_lr_scheduler,
+        optimizer_overrides,
+        reset_meters=reset_meters,
+    )
+
+    if (
+        extra_state is not None
+        and "best" in extra_state
+        and not reset_optimizer
+        and not reset_meters
+    ):
+        save_checkpoint.best = extra_state["best"]
+
+    if extra_state is not None and not reset_dataloader:
+        # restore iterator from checkpoint
+        itr_state = extra_state["train_iterator"]
+        epoch_itr = trainer.get_train_iterator(
+            epoch=itr_state["epoch"], load_dataset=True, **passthrough_args
+        )
+        epoch_itr.load_state_dict(itr_state)
+
+        # Preload the checkpoint for the task
+        task_cp_dict = extra_state.get(trainer.task.__class__.__name__, {})
+        if task_cp_dict and hasattr(trainer.task, "set_checkpoint_dict"):
+            trainer.task.set_checkpoint_dict(task_cp_dict)
+    else:
+        epoch_itr = trainer.get_train_iterator(
+            epoch=1, load_dataset=True, **passthrough_args
+        )
+
+    trainer.lr_step(epoch_itr.epoch)
+
+    return extra_state, epoch_itr
+
+
+def load_checkpoint_to_cpu(path, arg_overrides=None, load_on_all_ranks=False):
+    """Loads a checkpoint to CPU (with upgrading for backward compatibility).
+
+    If doing single-GPU training or if the checkpoint is only being loaded by at
+    most one process on each node (current default behavior is for only rank 0
+    to read the checkpoint from disk), load_on_all_ranks should be False to
+    avoid errors from torch.distributed not having been initialized or
+    torch.distributed.barrier() hanging.
+
+    If all processes on each node may be loading the checkpoint
+    simultaneously, load_on_all_ranks should be set to True to avoid I/O
+    conflicts.
+
+    There's currently no support for > 1 but < all processes loading the
+    checkpoint on each node.
+    """
+    local_path = PathManager.get_local_path(path)
+    # The locally cached file returned by get_local_path() may be stale for
+    # remote files that are periodically updated/overwritten (ex:
+    # checkpoint_last.pt) - so we remove the local copy, sync across processes
+    # (if needed), and then download a fresh copy.
+    if local_path != path and PathManager.path_requires_pathmanager(path):
+        try:
+            os.remove(local_path)
+        except FileNotFoundError:
+            # With potentially multiple processes removing the same file, the
+            # file being missing is benign (missing_ok isn't available until
+            # Python 3.8).
+            pass
+        if load_on_all_ranks:
+            torch.distributed.barrier()
+        local_path = PathManager.get_local_path(path)
+
+    with open(local_path, "rb") as f:
+        state = torch.load(f, map_location=torch.device("cpu"))
+
+    if "args" in state and state["args"] is not None and arg_overrides is not None:
+        args = state["args"]
+        for arg_name, arg_val in arg_overrides.items():
+            setattr(args, arg_name, arg_val)
+
+    if "cfg" in state and state["cfg"] is not None:
+
+        # hack to be able to set Namespace in dict config. this should be removed when we update to newer
+        # omegaconf version that supports object flags, or when we migrate all existing models
+        from omegaconf import __version__ as oc_version
+        from omegaconf import _utils
+
+        if oc_version < "2.2":
+            old_primitive = _utils.is_primitive_type
+            _utils.is_primitive_type = lambda _: True
+
+            state["cfg"] = OmegaConf.create(state["cfg"])
+
+            _utils.is_primitive_type = old_primitive
+            OmegaConf.set_struct(state["cfg"], True)
+        else:
+            state["cfg"] = OmegaConf.create(state["cfg"], flags={"allow_objects": True})
+
+        if arg_overrides is not None:
+            overwrite_args_by_name(state["cfg"], arg_overrides)
+
+    state = _upgrade_state_dict(state)
+    return state
+
+
+def load_model_ensemble(
+    filenames,
+    arg_overrides: Optional[Dict[str, Any]] = None,
+    task=None,
+    strict=True,
+    suffix="",
+    num_shards=1,
+    state=None,
+):
+    """Loads an ensemble of models.
+
+    Args:
+        filenames (List[str]): checkpoint files to load
+        arg_overrides (Dict[str,Any], optional): override model args that
+            were used during model training
+        task (fairseq.tasks.FairseqTask, optional): task to use for loading
+    """
+    assert not (
+        strict and num_shards > 1
+    ), "Cannot load state dict with strict=True and checkpoint shards > 1"
+    ensemble, args, _task = load_model_ensemble_and_task(
+        filenames,
+        arg_overrides,
+        task,
+        strict,
+        suffix,
+        num_shards,
+        state,
+    )
+    return ensemble, args
+
+
+def get_maybe_sharded_checkpoint_filename(
+    filename: str, suffix: str, shard_idx: int, num_shards: int
+) -> str:
+    orig_filename = filename
+    filename = filename.replace(".pt", suffix + ".pt")
+    fsdp_filename = filename[:-3] + f"-shard{shard_idx}.pt"
+    model_parallel_filename = orig_filename[:-3] + f"_part{shard_idx}.pt"
+    if PathManager.exists(fsdp_filename):
+        return fsdp_filename
+    elif num_shards > 1:
+        return model_parallel_filename
+    else:
+        return filename
+
+
+def load_model_ensemble_and_task(
+    filenames,
+    arg_overrides: Optional[Dict[str, Any]] = None,
+    task=None,
+    strict=True,
+    suffix="",
+    num_shards=1,
+    state=None,
+):
+    assert state is None or len(filenames) == 1
+
+    from fairseq import tasks
+
+    assert not (
+        strict and num_shards > 1
+    ), "Cannot load state dict with strict=True and checkpoint shards > 1"
+    ensemble = []
+    cfg = None
+    for filename in filenames:
+        orig_filename = filename
+        model_shard_state = {"shard_weights": [], "shard_metadata": []}
+        assert num_shards > 0
+        st = time.time()
+        for shard_idx in range(num_shards):
+            filename = get_maybe_sharded_checkpoint_filename(
+                orig_filename, suffix, shard_idx, num_shards
+            )
+
+            if not PathManager.exists(filename):
+                raise IOError("Model file not found: {}".format(filename))
+            if state is None:
+                state = load_checkpoint_to_cpu(filename, arg_overrides)
+            if "args" in state and state["args"] is not None:
+                cfg = convert_namespace_to_omegaconf(state["args"])
+            elif "cfg" in state and state["cfg"] is not None:
+                cfg = state["cfg"]
+            else:
+                raise RuntimeError(
+                    f"Neither args nor cfg exist in state keys = {state.keys()}"
+                )
+
+            if task is None:
+                task = tasks.setup_task(cfg.task, from_checkpoint=True)
+
+            if "task_state" in state:
+                task.load_state_dict(state["task_state"])
+
+            argspec = inspect.getfullargspec(task.build_model)
+
+            if "fsdp_metadata" in state and num_shards > 1:
+                model_shard_state["shard_weights"].append(state["model"])
+                model_shard_state["shard_metadata"].append(state["fsdp_metadata"])
+                # check FSDP import before the code goes too far
+                if not has_FSDP:
+                    raise ImportError(
+                        "Cannot find FullyShardedDataParallel. "
+                        "Please install fairscale with: pip install fairscale"
+                    )
+                if shard_idx == num_shards - 1:
+                    consolidated_model_state = FSDP.consolidate_shard_weights(
+                        shard_weights=model_shard_state["shard_weights"],
+                        shard_metadata=model_shard_state["shard_metadata"],
+                    )
+                    if "from_checkpoint" in argspec.args:
+                        model = task.build_model(cfg.model, from_checkpoint=True)
+                    else:
+                        model = task.build_model(cfg.model)
+                    if (
+                        "optimizer_history" in state
+                        and len(state["optimizer_history"]) > 0
+                        and "num_updates" in state["optimizer_history"][-1]
+                    ):
+                        model.set_num_updates(
+                            state["optimizer_history"][-1]["num_updates"]
+                        )
+                    model.load_state_dict(
+                        consolidated_model_state, strict=strict, model_cfg=cfg.model
+                    )
+            else:
+                # model parallel checkpoint or unsharded checkpoint
+                # support old external tasks
+
+                if "from_checkpoint" in argspec.args:
+                    model = task.build_model(cfg.model, from_checkpoint=True)
+                else:
+                    model = task.build_model(cfg.model)
+                if (
+                    "optimizer_history" in state
+                    and len(state["optimizer_history"]) > 0
+                    and "num_updates" in state["optimizer_history"][-1]
+                ):
+                    model.set_num_updates(state["optimizer_history"][-1]["num_updates"])
+                model.load_state_dict(
+                    state["model"], strict=strict, model_cfg=cfg.model
+                )
+
+            # reset state so it gets loaded for the next model in ensemble
+            state = None
+            if shard_idx % 10 == 0 and shard_idx > 0:
+                elapsed = time.time() - st
+                logger.info(
+                    f"Loaded {shard_idx} shards in {elapsed:.2f}s, {elapsed / (shard_idx+1):.2f}s/shard"
+                )
+
+        # build model for ensemble
+        ensemble.append(model)
+    return ensemble, cfg, task
+
+
+def load_model_ensemble_and_task_from_hf_hub(
+    model_id,
+    cache_dir: Optional[str] = None,
+    arg_overrides: Optional[Dict[str, Any]] = None,
+    **kwargs: Any,
+):
+    try:
+        from huggingface_hub import snapshot_download
+    except ImportError:
+        raise ImportError(
+            "You need to install huggingface_hub to use `load_from_hf_hub`. "
+            "See https://pypi.org/project/huggingface-hub/ for installation."
+        )
+
+    library_name = "fairseq"
+    cache_dir = cache_dir or (Path.home() / ".cache" / library_name).as_posix()
+    cache_dir = snapshot_download(
+        model_id, cache_dir=cache_dir, library_name=library_name, **kwargs
+    )
+
+    _arg_overrides = arg_overrides or {}
+    _arg_overrides["data"] = cache_dir
+    return load_model_ensemble_and_task(
+        [p.as_posix() for p in Path(cache_dir).glob("*.pt")],
+        arg_overrides=_arg_overrides,
+    )
+
+
+def checkpoint_paths(path, pattern=r"checkpoint(\d+)\.pt", keep_match=False):
+    """Retrieves all checkpoints found in `path` directory.
+
+    Checkpoints are identified by matching filename to the specified pattern. If
+    the pattern contains groups, the result will be sorted by the first group in
+    descending order.
+    """
+    pt_regexp = re.compile(pattern)
+    files = PathManager.ls(path)
+
+    entries = []
+    for i, f in enumerate(files):
+        m = pt_regexp.fullmatch(f)
+        if m is not None:
+            idx = float(m.group(1)) if len(m.groups()) > 0 else i
+            entries.append((idx, m.group(0)))
+    if keep_match:
+        return [(os.path.join(path, x[1]), x[0]) for x in sorted(entries, reverse=True)]
+    else:
+        return [os.path.join(path, x[1]) for x in sorted(entries, reverse=True)]
+
+
+def torch_persistent_save(obj, filename, async_write: bool = False):
+    if async_write:
+        with PathManager.opena(filename, "wb") as f:
+            _torch_persistent_save(obj, f)
+    else:
+        if PathManager.supports_rename(filename):
+            # do atomic save
+            with PathManager.open(filename + ".tmp", "wb") as f:
+                _torch_persistent_save(obj, f)
+            PathManager.rename(filename + ".tmp", filename)
+        else:
+            # fallback to non-atomic save
+            with PathManager.open(filename, "wb") as f:
+                _torch_persistent_save(obj, f)
+
+
+def _torch_persistent_save(obj, f):
+    if isinstance(f, str):
+        with PathManager.open(f, "wb") as h:
+            torch_persistent_save(obj, h)
+        return
+    for i in range(3):
+        try:
+            return torch.save(obj, f)
+        except Exception:
+            if i == 2:
+                logger.error(traceback.format_exc())
+                raise
+            else:
+                time.sleep(2.5)
+
+
+def _upgrade_state_dict(state):
+    """Helper for upgrading old model checkpoints."""
+
+    # add optimizer_history
+    if "optimizer_history" not in state:
+        state["optimizer_history"] = [
+            {"criterion_name": "CrossEntropyCriterion", "best_loss": state["best_loss"]}
+        ]
+        state["last_optimizer_state"] = state["optimizer"]
+        del state["optimizer"]
+        del state["best_loss"]
+    # move extra_state into sub-dictionary
+    if "epoch" in state and "extra_state" not in state:
+        state["extra_state"] = {
+            "epoch": state["epoch"],
+            "batch_offset": state["batch_offset"],
+            "val_loss": state["val_loss"],
+        }
+        del state["epoch"]
+        del state["batch_offset"]
+        del state["val_loss"]
+    # reduce optimizer history's memory usage (only keep the last state)
+    if "optimizer" in state["optimizer_history"][-1]:
+        state["last_optimizer_state"] = state["optimizer_history"][-1]["optimizer"]
+        for optim_hist in state["optimizer_history"]:
+            del optim_hist["optimizer"]
+    # record the optimizer class name
+    if "optimizer_name" not in state["optimizer_history"][-1]:
+        state["optimizer_history"][-1]["optimizer_name"] = "FairseqNAG"
+    # move best_loss into lr_scheduler_state
+    if "lr_scheduler_state" not in state["optimizer_history"][-1]:
+        state["optimizer_history"][-1]["lr_scheduler_state"] = {
+            "best": state["optimizer_history"][-1]["best_loss"]
+        }
+        del state["optimizer_history"][-1]["best_loss"]
+    # keep track of number of updates
+    if "num_updates" not in state["optimizer_history"][-1]:
+        state["optimizer_history"][-1]["num_updates"] = 0
+    # use stateful training data iterator
+    if "train_iterator" not in state["extra_state"]:
+        state["extra_state"]["train_iterator"] = {
+            "epoch": state["extra_state"].get("epoch", 0),
+            "iterations_in_epoch": state["extra_state"].get("batch_offset", 0),
+        }
+
+    # backward compatibility, cfg updates
+    if "args" in state and state["args"] is not None:
+        # old model checkpoints may not have separate source/target positions
+        if hasattr(state["args"], "max_positions") and not hasattr(
+            state["args"], "max_source_positions"
+        ):
+            state["args"].max_source_positions = state["args"].max_positions
+            state["args"].max_target_positions = state["args"].max_positions
+        # default to translation task
+        if not hasattr(state["args"], "task"):
+            state["args"].task = "translation"
+        # --raw-text and --lazy-load are deprecated
+        if getattr(state["args"], "raw_text", False):
+            state["args"].dataset_impl = "raw"
+        elif getattr(state["args"], "lazy_load", False):
+            state["args"].dataset_impl = "lazy"
+        # epochs start at 1
+        if state["extra_state"]["train_iterator"] is not None:
+            state["extra_state"]["train_iterator"]["epoch"] = max(
+                state["extra_state"]["train_iterator"].get("epoch", 1), 1
+            )
+        # --remove-bpe ==> --postprocess
+        if hasattr(state["args"], "remove_bpe"):
+            state["args"].post_process = state["args"].remove_bpe
+        # --min-lr ==> --stop-min-lr
+        if hasattr(state["args"], "min_lr"):
+            state["args"].stop_min_lr = state["args"].min_lr
+            del state["args"].min_lr
+        # binary_cross_entropy / kd_binary_cross_entropy => wav2vec criterion
+        if hasattr(state["args"], "criterion") and state["args"].criterion in [
+            "binary_cross_entropy",
+            "kd_binary_cross_entropy",
+        ]:
+            state["args"].criterion = "wav2vec"
+        # remove log_keys if it's None (criteria will supply a default value of [])
+        if hasattr(state["args"], "log_keys") and state["args"].log_keys is None:
+            delattr(state["args"], "log_keys")
+        # speech_pretraining => audio pretraining
+        if (
+            hasattr(state["args"], "task")
+            and state["args"].task == "speech_pretraining"
+        ):
+            state["args"].task = "audio_pretraining"
+        # audio_cpc => wav2vec
+        if hasattr(state["args"], "arch") and state["args"].arch == "audio_cpc":
+            state["args"].arch = "wav2vec"
+        # convert legacy float learning rate to List[float]
+        if hasattr(state["args"], "lr") and isinstance(state["args"].lr, float):
+            state["args"].lr = [state["args"].lr]
+        # convert task data arg to a string instead of List[string]
+        if (
+            hasattr(state["args"], "data")
+            and isinstance(state["args"].data, list)
+            and len(state["args"].data) > 0
+        ):
+            state["args"].data = state["args"].data[0]
+
+        state["cfg"] = convert_namespace_to_omegaconf(state["args"])
+
+    if "cfg" in state and state["cfg"] is not None:
+        cfg = state["cfg"]
+        with open_dict(cfg):
+            # any upgrades for Hydra-based configs
+            if (
+                "task" in cfg
+                and "eval_wer_config" in cfg.task
+                and isinstance(cfg.task.eval_wer_config.print_alignment, bool)
+            ):
+                cfg.task.eval_wer_config.print_alignment = "hard"
+            if "generation" in cfg and isinstance(cfg.generation.print_alignment, bool):
+                cfg.generation.print_alignment = (
+                    "hard" if cfg.generation.print_alignment else None
+                )
+            if (
+                "model" in cfg
+                and "w2v_args" in cfg.model
+                and cfg.model.w2v_args is not None
+                and (
+                    hasattr(cfg.model.w2v_args, "task") or "task" in cfg.model.w2v_args
+                )
+                and hasattr(cfg.model.w2v_args.task, "eval_wer_config")
+                and cfg.model.w2v_args.task.eval_wer_config is not None
+                and isinstance(
+                    cfg.model.w2v_args.task.eval_wer_config.print_alignment, bool
+                )
+            ):
+                cfg.model.w2v_args.task.eval_wer_config.print_alignment = "hard"
+
+    return state
+
+
+def prune_state_dict(state_dict, model_cfg: Optional[DictConfig]):
+    """Prune the given state_dict if desired for LayerDrop
+    (https://arxiv.org/abs/1909.11556).
+
+    Training with LayerDrop allows models to be robust to pruning at inference
+    time. This function prunes state_dict to allow smaller models to be loaded
+    from a larger model and re-maps the existing state_dict for this to occur.
+
+    It's called by functions that load models from checkpoints and does not
+    need to be called directly.
+    """
+    arch = None
+    if model_cfg is not None:
+        arch = (
+            model_cfg._name
+            if isinstance(model_cfg, DictConfig)
+            else getattr(model_cfg, "arch", None)
+        )
+
+    if not model_cfg or arch is None or arch == "ptt_transformer":
+        # args should not be none, but don't crash if it is.
+        return state_dict
+
+    encoder_layers_to_keep = getattr(model_cfg, "encoder_layers_to_keep", None)
+    decoder_layers_to_keep = getattr(model_cfg, "decoder_layers_to_keep", None)
+
+    if not encoder_layers_to_keep and not decoder_layers_to_keep:
+        return state_dict
+
+    # apply pruning
+    logger.info(
+        "Pruning model to specified layer configuration - this works best if the model was trained with LayerDrop"
+    )
+
+    def create_pruning_pass(layers_to_keep, layer_name):
+        keep_layers = sorted(
+            int(layer_string) for layer_string in layers_to_keep.split(",")
+        )
+        mapping_dict = {}
+        for i in range(len(keep_layers)):
+            mapping_dict[str(keep_layers[i])] = str(i)
+
+        regex = re.compile(r"^{layer}.*\.layers\.(\d+)".format(layer=layer_name))
+        return {"substitution_regex": regex, "mapping_dict": mapping_dict}
+
+    pruning_passes = []
+    if encoder_layers_to_keep:
+        pruning_passes.append(create_pruning_pass(encoder_layers_to_keep, "encoder"))
+    if decoder_layers_to_keep:
+        pruning_passes.append(create_pruning_pass(decoder_layers_to_keep, "decoder"))
+
+    new_state_dict = {}
+    for layer_name in state_dict.keys():
+        match = re.search(r"\.layers\.(\d+)\.", layer_name)
+        # if layer has no number in it, it is a supporting layer, such as an
+        # embedding
+        if not match:
+            new_state_dict[layer_name] = state_dict[layer_name]
+            continue
+
+        # otherwise, layer should be pruned.
+        original_layer_number = match.group(1)
+        # figure out which mapping dict to replace from
+        for pruning_pass in pruning_passes:
+            if original_layer_number in pruning_pass["mapping_dict"] and pruning_pass[
+                "substitution_regex"
+            ].search(layer_name):
+                new_layer_number = pruning_pass["mapping_dict"][original_layer_number]
+                substitution_match = pruning_pass["substitution_regex"].search(
+                    layer_name
+                )
+                new_state_key = (
+                    layer_name[: substitution_match.start(1)]
+                    + new_layer_number
+                    + layer_name[substitution_match.end(1) :]
+                )
+                new_state_dict[new_state_key] = state_dict[layer_name]
+
+    # Since layers are now pruned, *_layers_to_keep are no longer needed.
+    # This is more of "It would make it work fix" rather than a proper fix.
+    if isinstance(model_cfg, DictConfig):
+        context = open_dict(model_cfg)
+    else:
+        context = contextlib.ExitStack()
+    with context:
+        if hasattr(model_cfg, "encoder_layers_to_keep"):
+            model_cfg.encoder_layers_to_keep = None
+        if hasattr(model_cfg, "decoder_layers_to_keep"):
+            model_cfg.decoder_layers_to_keep = None
+
+    return new_state_dict
+
+
+def load_pretrained_component_from_model(
+    component: Union[FairseqEncoder, FairseqDecoder],
+    checkpoint: str,
+    strict: bool = True,
+):
+    """
+    Load a pretrained FairseqEncoder or FairseqDecoder from checkpoint into the
+    provided `component` object. If state_dict fails to load, there may be a
+    mismatch in the architecture of the corresponding `component` found in the
+    `checkpoint` file.
+    """
+    if not PathManager.exists(checkpoint):
+        raise IOError("Model file not found: {}".format(checkpoint))
+    state = load_checkpoint_to_cpu(checkpoint)
+    if isinstance(component, FairseqEncoder):
+        component_type = "encoder"
+    elif isinstance(component, FairseqDecoder):
+        component_type = "decoder"
+    else:
+        raise ValueError(
+            "component to load must be either a FairseqEncoder or "
+            "FairseqDecoder. Loading other component types are not supported."
+        )
+    component_state_dict = OrderedDict()
+    for key in state["model"].keys():
+        if key.startswith(component_type):
+            # encoder.input_layers.0.0.weight --> input_layers.0.0.weight
+            component_subkey = key[len(component_type) + 1 :]
+            component_state_dict[component_subkey] = state["model"][key]
+    component.load_state_dict(component_state_dict, strict=strict)
+    return component
+
+
+def verify_checkpoint_directory(save_dir: str) -> None:
+    if not os.path.exists(save_dir):
+        os.makedirs(save_dir, exist_ok=True)
+    temp_file_path = os.path.join(save_dir, "dummy")
+    try:
+        with open(temp_file_path, "w"):
+            pass
+    except OSError as e:
+        logger.warning(
+            "Unable to access checkpoint save directory: {}".format(save_dir)
+        )
+        raise e
+    else:
+        os.remove(temp_file_path)
+
+
+def save_ema_as_checkpoint(src_path, dst_path):
+    state = load_ema_from_checkpoint(src_path)
+    torch_persistent_save(state, dst_path)
+
+
+def load_ema_from_checkpoint(fpath):
+    """Loads exponential moving averaged (EMA) checkpoint from input and
+    returns a model with ema weights.
+
+    Args:
+      fpath: A string path of checkpoint to load from.
+
+    Returns:
+      A dict of string keys mapping to various values. The 'model' key
+      from the returned dict should correspond to an OrderedDict mapping
+      string parameter names to torch Tensors.
+    """
+    params_dict = collections.OrderedDict()
+    new_state = None
+
+    with PathManager.open(fpath, "rb") as f:
+        new_state = torch.load(
+            f,
+            map_location=(
+                lambda s, _: torch.serialization.default_restore_location(s, "cpu")
+            ),
+        )
+
+        # EMA model is stored in a separate "extra state"
+        model_params = new_state["extra_state"]["ema"]
+
+        for key in list(model_params.keys()):
+            p = model_params[key]
+            if isinstance(p, torch.HalfTensor):
+                p = p.float()
+            if key not in params_dict:
+                params_dict[key] = p.clone()
+                # NOTE: clone() is needed in case of p is a shared parameter
+            else:
+                raise ValueError("Key {} is repeated in EMA model params.".format(key))
+
+        if len(params_dict) == 0:
+            raise ValueError(
+                f"Input checkpoint path '{fpath}' does not contain "
+                "ema model weights, is this model trained with EMA?"
+            )
+
+    new_state["model"] = params_dict
+    return new_state