lightning/pytorch_lightning/accelerator_backends/ddp_backend.py

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2020-08-02 12:13:31 +00:00
# Copyright The PyTorch Lightning team.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License
import os
import torch
import subprocess
import sys
from time import sleep
import numpy as np
from os.path import abspath
from pytorch_lightning.utilities import NATIVE_AMP_AVALAIBLE
from pytorch_lightning.utilities.distributed import rank_zero_only
from pytorch_lightning import _logger as log
from typing import Optional
try:
from hydra.utils import to_absolute_path, get_original_cwd
from hydra.core.hydra_config import HydraConfig
except ImportError:
HYDRA_AVAILABLE = False
else:
HYDRA_AVAILABLE = True
try:
from apex import amp
except ImportError:
APEX_AVAILABLE = False
else:
APEX_AVAILABLE = True
class DDPBackend(object):
def __init__(self, trainer):
self.trainer = trainer
self.task_idx = None
def slurm_setup(self):
self.task_idx = int(os.environ['SLURM_LOCALID'])
def torchelastic_setup(self):
self.task_idx = int(os.environ['LOCAL_RANK'])
def train(self, model):
self.ddp_train(process_idx=self.task_idx, mp_queue=None, model=model)
def spawn_ddp_children(self, model):
port = os.environ['MASTER_PORT']
master_address = '127.0.0.1' if 'MASTER_ADDR' not in os.environ else os.environ['MASTER_ADDR']
os.environ['MASTER_PORT'] = f'{port}'
os.environ['MASTER_ADDR'] = f'{master_address}'
# allow the user to pass the node rank
node_rank = '0'
if 'NODE_RANK' in os.environ:
node_rank = os.environ['NODE_RANK']
if 'GROUP_RANK' in os.environ:
node_rank = os.environ['GROUP_RANK']
os.environ['NODE_RANK'] = node_rank
os.environ['LOCAL_RANK'] = '0'
# when user is using hydra find the absolute path
path_lib = abspath if not HYDRA_AVAILABLE else to_absolute_path
# pull out the commands used to run the script and resolve the abs file path
command = sys.argv
try:
full_path = path_lib(command[0])
except Exception as e:
full_path = abspath(command[0])
command[0] = full_path
# use the same python interpreter and actually running
command = [sys.executable] + command
# since this script sets the visible devices we replace the gpus flag with a number
num_gpus = os.environ['CUDA_VISIBLE_DEVICES'].split(',').__len__()
if '--gpus' in command:
gpu_flag_idx = command.index('--gpus')
command[gpu_flag_idx + 1] = f'{num_gpus}'
os.environ['WORLD_SIZE'] = f'{num_gpus * self.trainer.num_nodes}'
self.trainer.interactive_ddp_procs = []
for local_rank in range(1, self.trainer.num_processes):
env_copy = os.environ.copy()
env_copy['LOCAL_RANK'] = f'{local_rank}'
# start process
# if hydra is available and initialized, make sure to set the cwd correctly
cwd: Optional[str] = None
if HYDRA_AVAILABLE:
if HydraConfig.initialized():
cwd = get_original_cwd()
proc = subprocess.Popen(command, env=env_copy, cwd=cwd)
self.trainer.interactive_ddp_procs.append(proc)
# starting all processes at once can cause issues
# with dataloaders delay between 1-10 seconds
delay = np.random.uniform(1, 5, 1)[0]
sleep(delay)
local_rank = 0
results = self.ddp_train(local_rank, mp_queue=None, model=model, is_master=True)
del os.environ['WORLD_SIZE']
return results
def ddp_train(self, process_idx, mp_queue, model, is_master=False, proc_offset=0):
"""
Entry point for ddp
Args:
process_idx:
mp_queue: multiprocessing queue
model:
is_master:
proc_offset:
Returns:
"""
# offset the process id if requested
process_idx = process_idx + proc_offset
# show progressbar only on progress_rank 0
if (self.trainer.node_rank != 0 or process_idx != 0) and self.trainer.progress_bar_callback is not None:
self.trainer.progress_bar_callback.disable()
# determine which process we are and world size
self.trainer.local_rank = process_idx
self.trainer.global_rank = self.trainer.node_rank * self.trainer.num_processes + process_idx
self.trainer.world_size = self.trainer.num_nodes * self.trainer.num_processes
# set warning rank
rank_zero_only.rank = self.trainer.global_rank
# set up server using proc 0's ip address
# try to init for 20 times at max in case ports are taken
# where to store ip_table
model.trainer = self.trainer
model.init_ddp_connection(
self.trainer.global_rank,
self.trainer.world_size,
self.trainer.is_slurm_managing_tasks
)
# call setup after the ddp process has connected
self.trainer.call_setup_hook(model)
# on world_size=0 let everyone know training is starting
if self.trainer.is_global_zero:
log.info('-' * 100)
log.info(f'distributed_backend={self.trainer.distributed_backend}')
log.info(f'All DDP processes registered. Starting ddp with {self.trainer.world_size} processes')
log.info('-' * 100)
# CHOOSE OPTIMIZER
# allow for lr schedulers as well
optimizers, lr_schedulers, optimizer_frequencies = self.trainer.init_optimizers(model)
self.trainer.optimizers = optimizers
self.trainer.lr_schedulers = lr_schedulers
self.trainer.optimizer_frequencies = optimizer_frequencies
# MODEL
# copy model to each gpu
if self.trainer.on_gpu:
gpu_idx = process_idx
# when using ddp, the master process (proc 0) continues running as the main one
# this means that the local rank will always be 0
# (even if cuda visible devices has other visible gpus)
# this means that the master process needs to pull the 0th visible index as the device number
if is_master:
available_gpus = os.environ['CUDA_VISIBLE_DEVICES'].split(',')
gpu_idx = int(available_gpus[self.trainer.local_rank])
self.trainer.root_gpu = gpu_idx
torch.cuda.set_device(self.trainer.root_gpu)
model.cuda(self.trainer.root_gpu)
# set model properties before going into wrapper
self.trainer.copy_trainer_model_properties(model)
# AMP
# run through amp wrapper before going to distributed DP
# TODO: remove with dropping NVIDIA AMP support
if self.trainer.use_amp and not NATIVE_AMP_AVALAIBLE:
model, optimizers = model.configure_apex(amp, model, self.trainer.optimizers, self.trainer.amp_level)
self.trainer.optimizers = optimizers
self.trainer.reinit_scheduler_properties(self.trainer.optimizers, self.trainer.lr_schedulers)
# DDP2 uses all GPUs on the machine
if self.trainer.distributed_backend == 'ddp' or self.trainer.distributed_backend == 'ddp_spawn':
device_ids = [self.trainer.root_gpu]
else: # includes ddp_cpu
device_ids = None
# allow user to configure ddp
model = model.configure_ddp(model, device_ids)
# continue training routine
results = self.trainer.run_pretrain_routine(model)
# get original model
model = self.trainer.get_model()
# persist info in ddp_spawn
self.trainer.transfer_distrib_spawn_state_on_fit_end(model, mp_queue, results)
# clean up memory
torch.cuda.empty_cache()
if self.trainer.global_rank == 0 and self.trainer.distributed_backend not in ['ddp_spawn', 'ddp_cpu']:
return results