Source code for pytorch_lightning.utilities.seed
# Copyright The PyTorch Lightning team.
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# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
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# http://www.apache.org/licenses/LICENSE-2.0
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# Unless required by applicable law or agreed to in writing, software
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# See the License for the specific language governing permissions and
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"""Utilities to help with reproducibility of models."""
import logging
import os
import random
from contextlib import contextmanager
from random import getstate as python_get_rng_state
from random import setstate as python_set_rng_state
from typing import Any, Dict, Generator, Optional
import numpy as np
import torch
from pytorch_lightning.utilities.rank_zero import rank_zero_only, rank_zero_warn
log = logging.getLogger(__name__)
max_seed_value = np.iinfo(np.uint32).max
min_seed_value = np.iinfo(np.uint32).min
[docs]def seed_everything(seed: Optional[int] = None, workers: bool = False) -> int:
"""Function that sets seed for pseudo-random number generators in: pytorch, numpy, python.random In addition,
sets the following environment variables:
- `PL_GLOBAL_SEED`: will be passed to spawned subprocesses (e.g. ddp_spawn backend).
- `PL_SEED_WORKERS`: (optional) is set to 1 if ``workers=True``.
Args:
seed: the integer value seed for global random state in Lightning.
If `None`, will read seed from `PL_GLOBAL_SEED` env variable
or select it randomly.
workers: if set to ``True``, will properly configure all dataloaders passed to the
Trainer with a ``worker_init_fn``. If the user already provides such a function
for their dataloaders, setting this argument will have no influence. See also:
:func:`~pytorch_lightning.utilities.seed.pl_worker_init_function`.
"""
if seed is None:
env_seed = os.environ.get("PL_GLOBAL_SEED")
if env_seed is None:
seed = _select_seed_randomly(min_seed_value, max_seed_value)
rank_zero_warn(f"No seed found, seed set to {seed}")
else:
try:
seed = int(env_seed)
except ValueError:
seed = _select_seed_randomly(min_seed_value, max_seed_value)
rank_zero_warn(f"Invalid seed found: {repr(env_seed)}, seed set to {seed}")
elif not isinstance(seed, int):
seed = int(seed)
if not (min_seed_value <= seed <= max_seed_value):
rank_zero_warn(f"{seed} is not in bounds, numpy accepts from {min_seed_value} to {max_seed_value}")
seed = _select_seed_randomly(min_seed_value, max_seed_value)
# using `log.info` instead of `rank_zero_info`,
# so users can verify the seed is properly set in distributed training.
log.info(f"Global seed set to {seed}")
os.environ["PL_GLOBAL_SEED"] = str(seed)
random.seed(seed)
np.random.seed(seed)
torch.manual_seed(seed)
torch.cuda.manual_seed_all(seed)
os.environ["PL_SEED_WORKERS"] = f"{int(workers)}"
return seed
def _select_seed_randomly(min_seed_value: int = min_seed_value, max_seed_value: int = max_seed_value) -> int:
return random.randint(min_seed_value, max_seed_value)
[docs]def reset_seed() -> None:
"""Reset the seed to the value that :func:`pytorch_lightning.utilities.seed.seed_everything` previously set.
If :func:`pytorch_lightning.utilities.seed.seed_everything` is unused, this function will do nothing.
"""
seed = os.environ.get("PL_GLOBAL_SEED", None)
if seed is None:
return
workers = os.environ.get("PL_SEED_WORKERS", "0")
seed_everything(int(seed), workers=bool(int(workers)))
[docs]def pl_worker_init_function(worker_id: int, rank: Optional[int] = None) -> None: # pragma: no cover
"""The worker_init_fn that Lightning automatically adds to your dataloader if you previously set the seed with
``seed_everything(seed, workers=True)``.
See also the PyTorch documentation on
`randomness in DataLoaders <https://pytorch.org/docs/stable/notes/randomness.html#dataloader>`_.
"""
# implementation notes: https://github.com/pytorch/pytorch/issues/5059#issuecomment-817392562
global_rank = rank if rank is not None else rank_zero_only.rank
process_seed = torch.initial_seed()
# back out the base seed so we can use all the bits
base_seed = process_seed - worker_id
log.debug(
f"Initializing random number generators of process {global_rank} worker {worker_id} with base seed {base_seed}"
)
ss = np.random.SeedSequence([base_seed, worker_id, global_rank])
# use 128 bits (4 x 32-bit words)
np.random.seed(ss.generate_state(4))
# Spawn distinct SeedSequences for the PyTorch PRNG and the stdlib random module
torch_ss, stdlib_ss = ss.spawn(2)
torch.manual_seed(torch_ss.generate_state(1, dtype=np.uint64)[0])
# use 128 bits expressed as an integer
stdlib_seed = (stdlib_ss.generate_state(2, dtype=np.uint64).astype(object) * [1 << 64, 1]).sum()
random.seed(stdlib_seed)
def _collect_rng_states() -> Dict[str, Any]:
"""Collect the global random state of :mod:`torch`, :mod:`numpy` and Python."""
return {"torch": torch.get_rng_state(), "numpy": np.random.get_state(), "python": python_get_rng_state()}
def _set_rng_states(rng_state_dict: Dict[str, Any]) -> None:
"""Set the global random state of :mod:`torch`, :mod:`numpy` and Python in the current process."""
torch.set_rng_state(rng_state_dict["torch"])
np.random.set_state(rng_state_dict["numpy"])
version, state, gauss = rng_state_dict["python"]
python_set_rng_state((version, tuple(state), gauss))
[docs]@contextmanager
def isolate_rng() -> Generator[None, None, None]:
"""A context manager that resets the global random state on exit to what it was before entering.
It supports isolating the states for PyTorch, Numpy, and Python built-in random number generators.
Example:
>>> torch.manual_seed(1) # doctest: +ELLIPSIS
<torch._C.Generator object at ...>
>>> with isolate_rng():
... [torch.rand(1) for _ in range(3)]
[tensor([0.7576]), tensor([0.2793]), tensor([0.4031])]
>>> torch.rand(1)
tensor([0.7576])
"""
states = _collect_rng_states()
yield
_set_rng_states(states)
