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average_checkpoints.py
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average_checkpoints.py
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#!/usr/bin/env python3
# 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 argparse
import collections
import os
import re
import torch
from fairseq.file_io import PathManager
def average_checkpoints(inputs):
"""Loads checkpoints from inputs and returns a model with averaged weights.
Args:
inputs: An iterable of string paths of checkpoints 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()
params_keys = None
new_state = None
num_models = len(inputs)
for fpath in inputs:
with PathManager.open(fpath, "rb") as f:
state = torch.load(
f,
map_location=(
lambda s, _: torch.serialization.default_restore_location(s, "cpu")
),
)
# Copies over the settings from the first checkpoint
if new_state is None:
new_state = state
model_params = state["model"]
model_params_keys = list(model_params.keys())
if params_keys is None:
params_keys = model_params_keys
elif params_keys != model_params_keys:
raise KeyError(
"For checkpoint {}, expected list of params: {}, "
"but found: {}".format(f, params_keys, model_params_keys)
)
for k in params_keys:
p = model_params[k]
if isinstance(p, torch.HalfTensor):
p = p.float()
if k not in params_dict:
params_dict[k] = p.clone()
# NOTE: clone() is needed in case of p is a shared parameter
else:
params_dict[k] += p
averaged_params = collections.OrderedDict()
for k, v in params_dict.items():
averaged_params[k] = v
if averaged_params[k].is_floating_point():
averaged_params[k].div_(num_models)
else:
averaged_params[k] //= num_models
new_state["model"] = averaged_params
return new_state
def last_n_checkpoints(paths, n, update_based, upper_bound=None):
assert len(paths) == 1
path = paths[0]
if update_based:
pt_regexp = re.compile(r"checkpoint_\d+_(\d+)\.pt")
else:
pt_regexp = re.compile(r"checkpoint(\d+)\.pt")
files = PathManager.ls(path)
entries = []
for f in files:
m = pt_regexp.fullmatch(f)
if m is not None:
sort_key = int(m.group(1))
if upper_bound is None or sort_key <= upper_bound:
entries.append((sort_key, m.group(0)))
if len(entries) < n:
raise Exception(
"Found {} checkpoint files but need at least {}", len(entries), n
)
return [os.path.join(path, x[1]) for x in sorted(entries, reverse=True)[:n]]
def main():
parser = argparse.ArgumentParser(
description="Tool to average the params of input checkpoints to "
"produce a new checkpoint",
)
# fmt: off
parser.add_argument('--inputs', required=True, nargs='+',
help='Input checkpoint file paths.')
parser.add_argument('--output', required=True, metavar='FILE',
help='Write the new checkpoint containing the averaged weights to this path.')
num_group = parser.add_mutually_exclusive_group()
num_group.add_argument('--num-epoch-checkpoints', type=int,
help='if set, will try to find checkpoints with names checkpoint_xx.pt in the '
'path specified by input, and average last this many of them.')
num_group.add_argument('--num-update-checkpoints', type=int,
help='if set, will try to find checkpoints with names checkpoint_ee_xx.pt in the path specified by'
' input, and average last this many of them.')
num_group.add_argument('--num-best-checkpoints', type=int, default=0,
help='if set, will try to find checkpoints with names checkpoint_best_ee_xx.pt in the path specified by'
' input, and average last this many of them.')
parser.add_argument('--checkpoint-upper-bound', type=int,
help='when using --num-epoch-checkpoints, this will set an upper bound on which epoch to use, '
'when using --num-update-checkpoints, this will set an upper bound on which update to use'
'e.g., with --num-epoch-checkpoints=10 --checkpoint-upper-bound=50, checkpoints 41-50 would be'
' averaged.'
'e.g., with --num-update-checkpoints=10 --checkpoint-upper-bound=50000, checkpoints 40500-50000 would'
' be averaged assuming --save-interval-updates 500'
)
# fmt: on
args = parser.parse_args()
print(args)
num = None
is_update_based = False
if args.num_update_checkpoints is not None:
num = args.num_update_checkpoints
is_update_based = True
elif args.num_epoch_checkpoints is not None:
num = args.num_epoch_checkpoints
assert args.checkpoint_upper_bound is None or (
args.num_epoch_checkpoints is not None
or args.num_update_checkpoints is not None
), "--checkpoint-upper-bound requires --num-epoch-checkpoints or --num-update-checkpoints"
assert (
args.num_epoch_checkpoints is None or args.num_update_checkpoints is None
), "Cannot combine --num-epoch-checkpoints and --num-update-checkpoints"
if num is not None:
args.inputs = last_n_checkpoints(
args.inputs,
num,
is_update_based,
upper_bound=args.checkpoint_upper_bound,
)
print("averaging checkpoints: ", args.inputs)
if args.num_best_checkpoints > 0:
args.inputs = list(
sorted(
args.inputs,
key=lambda x: float(
os.path.basename(x).split("_")[-1].replace(".pt", "")
),
)
)
args.inputs = args.inputs[: args.num_best_checkpoints]
for path in args.inputs:
print(os.path.basename(path))
new_state = average_checkpoints(args.inputs)
with PathManager.open(args.output, "wb") as f:
torch.save(new_state, f)
print("Finished writing averaged checkpoint to {}".format(args.output))
if __name__ == "__main__":
main()