480 lines
16 KiB
Python
480 lines
16 KiB
Python
"""
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Lightning can automate saving and loading checkpoints
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=====================================================
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Checkpointing is enabled by default to the current working directory.
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To change the checkpoint path pass in::
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Trainer(default_save_path='/your/path/to/save/checkpoints')
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To modify the behavior of checkpointing pass in your own callback.
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.. code-block:: python
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from pytorch_lightning.callbacks import ModelCheckpoint
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# DEFAULTS used by the Trainer
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checkpoint_callback = ModelCheckpoint(
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filepath=os.getcwd(),
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save_top_k=1,
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verbose=True,
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monitor='val_loss',
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mode='min',
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prefix=''
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)
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trainer = Trainer(checkpoint_callback=checkpoint_callback)
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Restoring training session
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--------------------------
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You might want to not only load a model but also continue training it. Use this method to
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restore the trainer state as well. This will continue from the epoch and global step you last left off.
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However, the dataloaders will start from the first batch again (if you shuffled it shouldn't matter).
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Lightning will restore the session if you pass a logger with the same version and there's a saved checkpoint.
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.. code-block:: python
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from pytorch_lightning import Trainer
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trainer = Trainer(
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resume_from_checkpoint=PATH
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)
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# this fit call loads model weights and trainer state
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# the trainer continues seamlessly from where you left off
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# without having to do anything else.
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trainer.fit(model)
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The trainer restores:
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- global_step
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- current_epoch
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- All optimizers
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- All lr_schedulers
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- Model weights
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You can even change the logic of your model as long as the weights and "architecture" of
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the system isn't different. If you add a layer, for instance, it might not work.
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At a rough level, here's what happens inside Trainer :py:mod:`pytorch_lightning.base_module.model_saving.py`:
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.. code-block:: python
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self.global_step = checkpoint['global_step']
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self.current_epoch = checkpoint['epoch']
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# restore the optimizers
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optimizer_states = checkpoint['optimizer_states']
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for optimizer, opt_state in zip(self.optimizers, optimizer_states):
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optimizer.load_state_dict(opt_state)
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# restore the lr schedulers
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lr_schedulers = checkpoint['lr_schedulers']
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for scheduler, lrs_state in zip(self.lr_schedulers, lr_schedulers):
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scheduler['scheduler'].load_state_dict(lrs_state)
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# uses the model you passed into trainer
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model.load_state_dict(checkpoint['state_dict'])
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"""
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import os
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import re
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import signal
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import warnings
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from abc import ABC
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from argparse import Namespace
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from subprocess import call
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from typing import Union
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import torch
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import torch.distributed as torch_distrib
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from pytorch_lightning import _logger as log
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from pytorch_lightning.core.lightning import LightningModule
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from pytorch_lightning.loggers import LightningLoggerBase
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from pytorch_lightning.overrides.data_parallel import (
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LightningDistributedDataParallel,
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LightningDataParallel,
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)
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try:
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import torch_xla
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import torch_xla.core.xla_model as xm
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import torch_xla.distributed.xla_multiprocessing as xmp
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except ImportError:
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XLA_AVAILABLE = False
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else:
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XLA_AVAILABLE = True
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class TrainerIOMixin(ABC):
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# this is just a summary on variables used in this abstract class,
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# the proper values/initialisation should be done in child class
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model: LightningModule
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on_gpu: bool
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root_gpu: ...
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resume_from_checkpoint: ...
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use_ddp: bool
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use_ddp2: bool
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checkpoint_callback: ...
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proc_rank: int
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weights_save_path: str
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logger: Union[LightningLoggerBase, bool]
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early_stop_callback: ...
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lr_schedulers: ...
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optimizers: ...
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on_tpu: bool
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num_training_batches: int
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accumulate_grad_batches: int
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def get_model(self):
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is_dp_module = isinstance(self.model, (LightningDistributedDataParallel,
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LightningDataParallel))
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model = self.model.module if is_dp_module else self.model
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return model
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# --------------------
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# CHECK-POINTING
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# --------------------
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def restore_weights(self, model):
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"""
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We attempt to restore weights in this order:
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1. HPC weights.
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2. if no HPC weights restore checkpoint_path weights
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3. otherwise don't restore weights
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:param model:
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:return:
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"""
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# clear cache before restore
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if self.on_gpu:
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torch.cuda.empty_cache()
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# if script called from hpc resubmit, load weights
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did_restore_hpc_weights = self.restore_hpc_weights_if_needed(model)
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# clear cache after restore
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if self.on_gpu:
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torch.cuda.empty_cache()
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if not did_restore_hpc_weights:
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if self.resume_from_checkpoint is not None:
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self.restore(self.resume_from_checkpoint, on_gpu=self.on_gpu)
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# wait for all models to restore weights
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if self.use_ddp or self.use_ddp2:
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# wait for all processes to catch up
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torch_distrib.barrier()
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# wait for all models to restore weights
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if self.on_tpu and XLA_AVAILABLE:
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# wait for all processes to catch up
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torch_xla.core.xla_model.rendezvous("pl.TrainerIOMixin.restore_weights")
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# clear cache after restore
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if self.on_gpu:
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torch.cuda.empty_cache()
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# --------------------
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# HPC SIGNAL HANDLING
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# --------------------
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def register_slurm_signal_handlers(self):
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# see if we're using slurm (not interactive)
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on_slurm = False
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try:
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job_name = os.environ['SLURM_JOB_NAME']
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if job_name != 'bash':
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on_slurm = True
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except Exception as e:
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pass
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if on_slurm:
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log.info('Set SLURM handle signals.')
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signal.signal(signal.SIGUSR1, self.sig_handler)
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signal.signal(signal.SIGTERM, self.term_handler)
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def sig_handler(self, signum, frame): # pragma: no-cover
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if self.proc_rank == 0:
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# save weights
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log.info('handling SIGUSR1')
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self.hpc_save(self.weights_save_path, self.logger)
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# find job id
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job_id = os.environ['SLURM_JOB_ID']
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cmd = 'scontrol requeue {}'.format(job_id)
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# requeue job
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log.info(f'requeing job {job_id}...')
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result = call(cmd, shell=True)
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# print result text
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if result == 0:
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log.info(f'requeued exp {job_id}')
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else:
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log.info('requeue failed...')
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# close experiment to avoid issues
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self.logger.close()
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def term_handler(self, signum, frame):
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# save
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log.info("bypassing sigterm")
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# --------------------
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# MODEL SAVE CHECKPOINT
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# --------------------
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def _atomic_save(self, checkpoint, filepath):
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"""Saves a checkpoint atomically, avoiding the creation of incomplete checkpoints.
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This will create a temporary checkpoint with a suffix of ``.part``, then copy it to the final location once
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saving is finished.
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Args:
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checkpoint (object): The object to save.
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Built to be used with the ``dump_checkpoint`` method, but can deal with anything which ``torch.save``
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accepts.
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filepath (str|pathlib.Path): The path to which the checkpoint will be saved.
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This points to the file that the checkpoint will be stored in.
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"""
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tmp_path = str(filepath) + ".part"
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torch.save(checkpoint, tmp_path)
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os.replace(tmp_path, filepath)
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def save_checkpoint(self, filepath):
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checkpoint = self.dump_checkpoint()
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if self.proc_rank == 0:
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# do the actual save
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try:
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self._atomic_save(checkpoint, filepath)
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except AttributeError:
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if 'hparams' in checkpoint:
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del checkpoint['hparams']
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self._atomic_save(checkpoint, filepath)
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def restore(self, checkpoint_path, on_gpu):
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"""
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Restore training state from checkpoint.
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Also restores all training state like:
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- epoch
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- callbacks
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- schedulers
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- optimizer
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:param checkpoint_path:
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:param on_gpu:
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:return:
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"""
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# if on_gpu:
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# checkpoint = torch.load(checkpoint_path)
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# else:
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# load on CPU first
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checkpoint = torch.load(checkpoint_path, map_location=lambda storage, loc: storage)
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# load model state
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model = self.get_model()
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# load the state_dict on the model automatically
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model.load_state_dict(checkpoint['state_dict'])
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if on_gpu:
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model.cuda(self.root_gpu)
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# load training state (affects trainer only)
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self.restore_training_state(checkpoint)
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def dump_checkpoint(self):
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checkpoint = {
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'epoch': self.current_epoch + 1,
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'global_step': self.global_step + 1,
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}
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if self.checkpoint_callback is not None and self.checkpoint_callback is not False:
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checkpoint['checkpoint_callback_best'] = self.checkpoint_callback.best
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if self.early_stop_callback is not None and self.checkpoint_callback is not False:
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checkpoint['early_stop_callback_wait'] = self.early_stop_callback.wait
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checkpoint['early_stop_callback_patience'] = self.early_stop_callback.patience
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# save optimizers
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optimizer_states = []
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for i, optimizer in enumerate(self.optimizers):
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optimizer_states.append(optimizer.state_dict())
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checkpoint['optimizer_states'] = optimizer_states
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# save lr schedulers
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lr_schedulers = []
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for scheduler in self.lr_schedulers:
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lr_schedulers.append(scheduler['scheduler'].state_dict())
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checkpoint['lr_schedulers'] = lr_schedulers
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# add the hparams and state_dict from the model
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model = self.get_model()
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checkpoint['state_dict'] = model.state_dict()
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if hasattr(model, "hparams"):
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is_namespace = isinstance(model.hparams, Namespace)
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checkpoint['hparams'] = vars(model.hparams) if is_namespace else model.hparams
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checkpoint['hparams_type'] = 'namespace' if is_namespace else 'dict'
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else:
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warnings.warn(
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"Did not find hyperparameters at model.hparams. Saving checkpoint without"
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" hyperparameters"
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)
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# give the model a chance to add a few things
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model.on_save_checkpoint(checkpoint)
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return checkpoint
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# --------------------
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# HPC IO
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# --------------------
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def restore_hpc_weights_if_needed(self, model):
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"""
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If there is a set of hpc weights, use as signal to restore model
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:param model:
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:return:
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"""
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did_restore = False
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# look for hpc weights
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folderpath = self.weights_save_path
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if os.path.exists(folderpath):
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files = os.listdir(folderpath)
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hpc_weight_paths = [x for x in files if 'hpc_ckpt' in x]
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# if hpc weights exist restore model
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if len(hpc_weight_paths) > 0:
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self.hpc_load(folderpath, self.on_gpu)
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did_restore = True
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return did_restore
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def restore_training_state(self, checkpoint):
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"""
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Restore trainer state.
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Model will get its change to update
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:param checkpoint:
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:return:
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"""
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if self.checkpoint_callback is not None and self.checkpoint_callback is not False:
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self.checkpoint_callback.best = checkpoint['checkpoint_callback_best']
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if self.early_stop_callback is not None and self.early_stop_callback is not False:
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self.early_stop_callback.wait = checkpoint['early_stop_callback_wait']
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self.early_stop_callback.patience = checkpoint['early_stop_callback_patience']
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self.global_step = checkpoint['global_step']
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self.current_epoch = checkpoint['epoch']
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# Division deals with global step stepping once per accumulated batch
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# Inequality deals with different global step for odd vs even num_training_batches
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n_accum = 1 if self.accumulate_grad_batches is None else self.accumulate_grad_batches
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expected_steps = self.num_training_batches / n_accum
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if self.num_training_batches != 0 and self.global_step % expected_steps > 1:
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warnings.warn(
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"You're resuming from a checkpoint that ended mid-epoch. "
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"This can cause unreliable results if further training is done, "
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"consider using an end of epoch checkpoint. "
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)
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# restore the optimizers
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optimizer_states = checkpoint['optimizer_states']
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for optimizer, opt_state in zip(self.optimizers, optimizer_states):
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optimizer.load_state_dict(opt_state)
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# move optimizer to GPU 1 weight at a time
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# avoids OOM
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if self.root_gpu is not None:
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for state in optimizer.state.values():
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for k, v in state.items():
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if isinstance(v, torch.Tensor):
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state[k] = v.cuda(self.root_gpu)
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# restore the lr schedulers
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lr_schedulers = checkpoint['lr_schedulers']
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for scheduler, lrs_state in zip(self.lr_schedulers, lr_schedulers):
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scheduler['scheduler'].load_state_dict(lrs_state)
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# ----------------------------------
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# PRIVATE OPS
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# ----------------------------------
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def hpc_save(self, folderpath: str, logger):
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# make sure the checkpoint folder exists
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os.makedirs(folderpath, exist_ok=True)
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# save logger to make sure we get all the metrics
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logger.save()
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ckpt_number = self.max_ckpt_in_folder(folderpath) + 1
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if not os.path.exists(folderpath):
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os.makedirs(folderpath, exist_ok=True)
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filepath = os.path.join(folderpath, f'hpc_ckpt_{ckpt_number}.ckpt')
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# give model a chance to do something on hpc_save
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model = self.get_model()
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checkpoint = self.dump_checkpoint()
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model.on_hpc_save(checkpoint)
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# do the actual save
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# TODO: fix for anything with multiprocess DP, DDP, DDP2
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try:
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self._atomic_save(checkpoint, filepath)
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except AttributeError:
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if 'hparams' in checkpoint:
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del checkpoint['hparams']
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self._atomic_save(checkpoint, filepath)
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return filepath
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def hpc_load(self, folderpath, on_gpu):
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filepath = '{}/hpc_ckpt_{}.ckpt'.format(folderpath, self.max_ckpt_in_folder(folderpath))
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# load on CPU first
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checkpoint = torch.load(filepath, map_location=lambda storage, loc: storage)
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# load model state
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model = self.get_model()
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# load the state_dict on the model automatically
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model.load_state_dict(checkpoint['state_dict'])
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if self.root_gpu is not None:
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model.cuda(self.root_gpu)
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# load training state (affects trainer only)
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self.restore_training_state(checkpoint)
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# call model hook
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model.on_hpc_load(checkpoint)
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log.info(f'restored hpc model from: {filepath}')
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def max_ckpt_in_folder(self, path, name_key='ckpt_'):
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files = os.listdir(path)
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files = [x for x in files if name_key in x]
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if len(files) == 0:
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return 0
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ckpt_vs = []
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for name in files:
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name = name.split(name_key)[-1]
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name = re.sub('[^0-9]', '', name)
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ckpt_vs.append(int(name))
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return max(ckpt_vs)
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