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# Copyright (c) OpenMMLab. All rights reserved. | |
# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved | |
import functools | |
import os | |
import socket | |
import subprocess | |
from collections import OrderedDict | |
from typing import Callable, List, Optional, Tuple | |
import torch | |
import torch.multiprocessing as mp | |
from torch import distributed as dist | |
from torch._utils import (_flatten_dense_tensors, _take_tensors, | |
_unflatten_dense_tensors) | |
def is_mps_available() -> bool: | |
"""Return True if mps devices exist. | |
It's specialized for mac m1 chips and require torch version 1.12 or higher. | |
""" | |
try: | |
import torch | |
return hasattr(torch.backends, | |
'mps') and torch.backends.mps.is_available() | |
except Exception: | |
return False | |
def _find_free_port() -> str: | |
# Copied from https://github.com/facebookresearch/detectron2/blob/main/detectron2/engine/launch.py # noqa: E501 | |
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) | |
# Binding to port 0 will cause the OS to find an available port for us | |
sock.bind(('', 0)) | |
port = sock.getsockname()[1] | |
sock.close() | |
# NOTE: there is still a chance the port could be taken by other processes. | |
return port | |
def _is_free_port(port: int) -> bool: | |
ips = socket.gethostbyname_ex(socket.gethostname())[-1] | |
ips.append('localhost') | |
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s: | |
return all(s.connect_ex((ip, port)) != 0 for ip in ips) | |
def init_dist(launcher: str, backend: str = 'nccl', **kwargs) -> None: | |
if mp.get_start_method(allow_none=True) is None: | |
mp.set_start_method('spawn') | |
if launcher == 'pytorch': | |
_init_dist_pytorch(backend, **kwargs) | |
elif launcher == 'mpi': | |
_init_dist_mpi(backend, **kwargs) | |
elif launcher == 'slurm': | |
_init_dist_slurm(backend, **kwargs) | |
else: | |
raise ValueError(f'Invalid launcher type: {launcher}') | |
def _init_dist_pytorch(backend: str, **kwargs) -> None: | |
# TODO: use local_rank instead of rank % num_gpus | |
rank = int(os.environ['RANK']) | |
num_gpus = torch.cuda.device_count() | |
torch.cuda.set_device(rank % num_gpus) | |
dist.init_process_group(backend=backend, **kwargs) | |
def _init_dist_mpi(backend: str, **kwargs) -> None: | |
local_rank = int(os.environ['OMPI_COMM_WORLD_LOCAL_RANK']) | |
torch.cuda.set_device(local_rank) | |
if 'MASTER_PORT' not in os.environ: | |
# 29500 is torch.distributed default port | |
os.environ['MASTER_PORT'] = '29500' | |
if 'MASTER_ADDR' not in os.environ: | |
raise KeyError('The environment variable MASTER_ADDR is not set') | |
os.environ['WORLD_SIZE'] = os.environ['OMPI_COMM_WORLD_SIZE'] | |
os.environ['RANK'] = os.environ['OMPI_COMM_WORLD_RANK'] | |
dist.init_process_group(backend=backend, **kwargs) | |
def _init_dist_slurm(backend: str, port: Optional[int] = None) -> None: | |
"""Initialize slurm distributed training environment. | |
If argument ``port`` is not specified, then the master port will be system | |
environment variable ``MASTER_PORT``. If ``MASTER_PORT`` is not in system | |
environment variable, then a default port ``29500`` will be used. | |
Args: | |
backend (str): Backend of torch.distributed. | |
port (int, optional): Master port. Defaults to None. | |
""" | |
proc_id = int(os.environ['SLURM_PROCID']) | |
ntasks = int(os.environ['SLURM_NTASKS']) | |
node_list = os.environ['SLURM_NODELIST'] | |
num_gpus = torch.cuda.device_count() | |
torch.cuda.set_device(proc_id % num_gpus) | |
addr = subprocess.getoutput( | |
f'scontrol show hostname {node_list} | head -n1') | |
# specify master port | |
if port is not None: | |
os.environ['MASTER_PORT'] = str(port) | |
elif 'MASTER_PORT' in os.environ: | |
pass # use MASTER_PORT in the environment variable | |
else: | |
# if torch.distributed default port(29500) is available | |
# then use it, else find a free port | |
if _is_free_port(29500): | |
os.environ['MASTER_PORT'] = '29500' | |
else: | |
os.environ['MASTER_PORT'] = str(_find_free_port()) | |
# use MASTER_ADDR in the environment variable if it already exists | |
if 'MASTER_ADDR' not in os.environ: | |
os.environ['MASTER_ADDR'] = addr | |
os.environ['WORLD_SIZE'] = str(ntasks) | |
os.environ['LOCAL_RANK'] = str(proc_id % num_gpus) | |
os.environ['RANK'] = str(proc_id) | |
dist.init_process_group(backend=backend) | |
def get_dist_info() -> Tuple[int, int]: | |
if dist.is_available() and dist.is_initialized(): | |
rank = dist.get_rank() | |
world_size = dist.get_world_size() | |
else: | |
rank = 0 | |
world_size = 1 | |
return rank, world_size | |
def master_only(func: Callable) -> Callable: | |
def wrapper(*args, **kwargs): | |
rank, _ = get_dist_info() | |
if rank == 0: | |
return func(*args, **kwargs) | |
return wrapper | |
def allreduce_params(params: List[torch.nn.Parameter], | |
coalesce: bool = True, | |
bucket_size_mb: int = -1) -> None: | |
"""Allreduce parameters. | |
Args: | |
params (list[torch.nn.Parameter]): List of parameters or buffers | |
of a model. | |
coalesce (bool, optional): Whether allreduce parameters as a whole. | |
Defaults to True. | |
bucket_size_mb (int, optional): Size of bucket, the unit is MB. | |
Defaults to -1. | |
""" | |
_, world_size = get_dist_info() | |
if world_size == 1: | |
return | |
params = [param.data for param in params] | |
if coalesce: | |
_allreduce_coalesced(params, world_size, bucket_size_mb) | |
else: | |
for tensor in params: | |
dist.all_reduce(tensor.div_(world_size)) | |
def allreduce_grads(params: List[torch.nn.Parameter], | |
coalesce: bool = True, | |
bucket_size_mb: int = -1) -> None: | |
"""Allreduce gradients. | |
Args: | |
params (list[torch.nn.Parameter]): List of parameters of a model. | |
coalesce (bool, optional): Whether allreduce parameters as a whole. | |
Defaults to True. | |
bucket_size_mb (int, optional): Size of bucket, the unit is MB. | |
Defaults to -1. | |
""" | |
grads = [ | |
param.grad.data for param in params | |
if param.requires_grad and param.grad is not None | |
] | |
_, world_size = get_dist_info() | |
if world_size == 1: | |
return | |
if coalesce: | |
_allreduce_coalesced(grads, world_size, bucket_size_mb) | |
else: | |
for tensor in grads: | |
dist.all_reduce(tensor.div_(world_size)) | |
def _allreduce_coalesced(tensors: torch.Tensor, | |
world_size: int, | |
bucket_size_mb: int = -1) -> None: | |
if bucket_size_mb > 0: | |
bucket_size_bytes = bucket_size_mb * 1024 * 1024 | |
buckets = _take_tensors(tensors, bucket_size_bytes) | |
else: | |
buckets = OrderedDict() | |
for tensor in tensors: | |
tp = tensor.type() | |
if tp not in buckets: | |
buckets[tp] = [] | |
buckets[tp].append(tensor) | |
buckets = buckets.values() | |
for bucket in buckets: | |
flat_tensors = _flatten_dense_tensors(bucket) | |
dist.all_reduce(flat_tensors) | |
flat_tensors.div_(world_size) | |
for tensor, synced in zip( | |
bucket, _unflatten_dense_tensors(flat_tensors, bucket)): | |
tensor.copy_(synced) | |