import time
import platform
import threading
import queue
from typing import Iterable, Callable, Optional, Any, Union
from collections import defaultdict
import torch
import torch.multiprocessing as tm
from ding.torch_utils import to_device
from ding.utils import LockContext, LockContextType
from .base_dataloader import IDataLoader
from .collate_fn import default_collate
[docs]class AsyncDataLoader(IDataLoader):
r"""
Overview:
An asynchronous dataloader.
Interface:
__init__, __iter__, __next__, close
"""
[docs] def __init__(
self,
data_source: Union[Callable, dict],
batch_size: int,
device: str,
chunk_size: Optional[int] = None,
collate_fn: Optional[Callable] = None,
num_workers: int = 0
) -> None:
"""
Overview:
Init dataloader with input parameters.
If ``data_source`` is ``dict``, data will only be processed in ``get_data_thread`` and put into
``async_train_queue``.
If ``data_source`` is ``Callable``, data will be processed by implementing functions, and can be sorted
in two types:
- ``num_workers`` == 0 or 1: Only main worker will process it and put into ``async_train_queue``.
- ``num_workers`` > 1: Main worker will divide a job into several pieces, push every job into \
``job_queue``; Then slave workers get jobs and implement; Finally they will push procesed data \
into ``async_train_queue``.
At the last step, if ``device`` contains "cuda", data in ``async_train_queue`` will be transferred to
``cuda_queue`` for uer to access.
Arguments:
- data_source (:obj:`Union[Callable, dict]`): The data source, e.g. function to be implemented(Callable), \
replay buffer's real data(dict), etc.
- batch_size (:obj:`int`): Batch size.
- device (:obj:`str`): Device.
- chunk_size (:obj:`int`): The size of a chunked piece in a batch, should exactly divide ``batch_size``, \
only function when there are more than 1 worker.
- collate_fn (:obj:`Callable`): The function which is used to collate batch size into each data field.
- num_workers (:obj:`int`): Number of extra workers. \
0 or 1 means only 1 main worker and no extra ones, i.e. Multiprocessing is disabled. \
More than 1 means multiple workers implemented by multiprocessing are to processs data respectively.
"""
self.data_source = data_source
self.batch_size = batch_size
self.device = device
self.use_cuda = 'cuda' in self.device
if self.use_cuda:
self.stream = torch.cuda.Stream()
if chunk_size is None:
self.chunk_size = 1
else:
self.chunk_size = chunk_size
assert self.batch_size >= self.chunk_size and self.batch_size % self.chunk_size == 0, '{}/{}'.format(
self.batch_size, self.chunk_size
)
if collate_fn is None:
self.collate_fn = default_collate
else:
self.collate_fn = collate_fn
self.num_workers = num_workers
if self.num_workers < 0:
raise ValueError(
'"num_workers" should be non-negative; '
'Use num_workers = 0 or 1 to disable multiprocessing.'
)
# Up to "2 * num_workers" pieces of data will be stored in dataloader, waiting for learner to get.
# Up to "2 * num_workers" jobs will be stored in dataloader, waiting for slave process to get and accomplish.
queue_maxsize = max(1, self.num_workers) * 2
self.queue_maxsize = queue_maxsize
# For multiprocessing: Use ``spawn`` on Windows, ``fork`` on other platforms.
context_str = 'spawn' if platform.system().lower() == 'windows' else 'fork'
self.mp_context = tm.get_context(context_str)
self.manager = self.mp_context.Manager()
# ``async_train_queue`` is the queue to store processed data.
# User can directly access data if don't use cuda; Otherwise, user will access data from ``cuda_queue``.
self.async_train_queue = self.mp_context.Queue(maxsize=queue_maxsize)
self.end_flag = False
# Multiprocessing workers: If num_workers > 1, more than 1 worker are to process data.
if self.num_workers > 1:
self.batch_id = self.mp_context.Value('i', 0)
self.cur_batch = self.mp_context.Value('i', 0)
if self.batch_size != self.chunk_size:
# job_result {batch_id: result_list} is used to store processed result in temporal.
self.job_result = self.manager.dict()
self.job_result_lock = LockContext(type_=LockContextType.PROCESS_LOCK)
self.job_queue = self.mp_context.Queue(maxsize=queue_maxsize)
self.worker = [
self.mp_context.Process(
target=self._worker_loop, args=(), name='dataloader_worker{}_{}'.format(i, time.time())
) for i in range(self.num_workers)
]
for w in self.worker:
w.daemon = True
w.start()
print('Using {} workers to load data'.format(self.num_workers))
# Parent and child pipes. Used by ``async_process`` and ``get_data_thread`` to coordinate.
p, c = self.mp_context.Pipe()
# Async process (Main worker): Process data if num_workers <= 1; Assign job to other workers if num_workers > 1.
self.async_process = self.mp_context.Process(target=self._async_loop, args=(p, c))
self.async_process.daemon = True
self.async_process.start()
# Get data thread: Get data from ``data_source`` and send it to ``async_process``.`
self.get_data_thread = threading.Thread(target=self._get_data, args=(p, c))
self.get_data_thread.daemon = True
self.get_data_thread.start()
# Cuda thread: If use cuda, data in ``async_train_queue`` will be transferred to ``cuda_queue``;
# Then user will access data from ``cuda_queue``.
if self.use_cuda:
self.cuda_queue = queue.Queue(maxsize=queue_maxsize)
self.cuda_thread = threading.Thread(target=self._cuda_loop, args=(), name='dataloader_cuda')
self.cuda_thread.daemon = True
self.cuda_thread.start()
[docs] def __iter__(self) -> Iterable:
"""
Overview:
Return the iterable self as an iterator.
Returns:
- self (:obj:`Iterable`): Self as an iterator.
"""
return self
def _get_data(self, p: tm.multiprocessing.connection, c: tm.multiprocessing.connection) -> None:
"""
Overview:
Init dataloader with input parameters. Will run as a thread through ``self.get_data_thread``.
Arguments:
- p (:obj:`tm.multiprocessing.connection`): Parent connection.
- c (:obj:`tm.multiprocessing.connection`): Child connection.
"""
c.close() # Close unused c, only use p
while not self.end_flag:
if not p.poll(timeout=0.2):
time.sleep(0.01)
continue
try:
cmd = p.recv()
except EOFError:
break
if cmd == 'get_data':
# Main worker asks for data.
data = self.data_source(self.batch_size)
# ``data`` can be callable, e.g. a function to read data from file, therefore we can divide
# this job to pieces, assign to every slave worker and accomplish jobs asynchronously.
# But if we get a list of dicts, which means the data has already been processed and
# can be used directly, we can put it directly in async_train_queue and wait it
# to be accessed by a user, e.g. learner.
if isinstance(data[0], dict):
data = self.collate_fn(data)
self.async_train_queue.put(data)
p.send('pass')
else:
p.send(data)
p.close()
def _async_loop(self, p: tm.multiprocessing.connection, c: tm.multiprocessing.connection) -> None:
"""
Overview:
Main worker process. Run through ``self.async_process``.
Firstly, get data from ``self.get_data_thread``.
If multiple workers, put data in ``self.job_queue`` for further multiprocessing operation;
If only one worker, process data and put directly into ``self.async_train_queue``.
Arguments:
- p (:obj:`tm.multiprocessing.connection`): Parent connection.
- c (:obj:`tm.multiprocessing.connection`): Child connection.
"""
p.close() # Close unused p, only use c
while not self.end_flag:
if self.num_workers > 1:
# Multiple workers: Put jobs (chunked data) into job_queue
if self.job_queue.full():
time.sleep(0.001)
else:
# Get data from ``_get_data`` thread.
c.send('get_data')
data = c.recv()
if isinstance(data, str) and data == 'pass':
continue
# Get data to be processed, chunk it into pieces and put them into job_queue.
chunk_num = self.batch_size // self.chunk_size
with self.batch_id.get_lock():
for i in range(chunk_num):
start, end = i * self.chunk_size, (i + 1) * self.chunk_size
self.job_queue.put({'batch_id': self.batch_id.value, 'job': data[start:end]})
self.batch_id.value = (self.batch_id.value + 1) % self.queue_maxsize # Increment batch_id
time.sleep(0.001)
else:
# Only one worker: Process data and directly put it into async_train_queue
if self.async_train_queue.full():
time.sleep(0.001)
else:
c.send('get_data')
data = c.recv()
if isinstance(data, str) and data == 'pass':
continue
data = [fn() for fn in data] # Implement functions in list ``data``.
data = self.collate_fn(data)
self.async_train_queue.put(data)
c.close()
def _worker_loop(self) -> None:
"""
Overview:
Worker process. Run through each element in list ``self.worker``.
Get data job from ``self.job_queue``, process it and then put into ``self.async_train_queue``.
Only function when ``self.num_workers`` > 1, which means using multiprocessing.
"""
while not self.end_flag:
if self.job_queue.empty() or self.async_train_queue.full():
# No left job to be done, or finished job have no space to store.
time.sleep(0.01)
continue
else:
try:
element = self.job_queue.get()
except (ConnectionResetError, ConnectionRefusedError) as e:
break
batch_id, job = element['batch_id'], element['job']
# Process the assigned data.
data = [fn() for fn in job] # Only function-type job will arrive here, dict-type will not
if len(data) == self.batch_size == self.chunk_size:
# Data not chunked: Finish the assigned one means finishing a whole batch.
data = self.collate_fn(data)
while batch_id != self.cur_batch.value:
time.sleep(0.01)
self.async_train_queue.put(data)
# Directly update cur_batch, since a whole batch is finished
with self.cur_batch.get_lock():
self.cur_batch.value = (self.cur_batch.value + 1) % self.queue_maxsize
else:
# Data chunked: Must wait for all chunked pieces in a batch to be accomplished.
finish_flag = False # indicate whether a whole batch is accomplished
with self.job_result_lock:
if batch_id not in self.job_result:
# The first one in a batch
self.job_result[batch_id] = data
elif len(self.job_result[batch_id]) + len(data) == self.batch_size:
# The last one in a batch
data += self.job_result.pop(batch_id)
assert batch_id not in self.job_result
finish_flag = True
else:
# Middle pieces in a batch
self.job_result[batch_id] += data
if finish_flag:
data = self.collate_fn(data)
while batch_id != self.cur_batch.value:
time.sleep(0.01)
self.async_train_queue.put(data)
with self.cur_batch.get_lock():
self.cur_batch.value = (self.cur_batch.value + 1) % self.queue_maxsize
# If ``self.end_flag`` is True, clear and close job_queue, because _worker_loop gets jobs from job_queue.
while not self.job_queue.empty():
try:
_ = self.job_queue.get()
except Exception as e:
break
self.job_queue.close()
self.job_queue.join_thread()
def _cuda_loop(self) -> None:
"""
Overview:
Only when using cuda, would this be run as a thread through ``self.cuda_thread``.
Get data from ``self.async_train_queue``, change its device and put it into ``self.cuda_queue``
"""
with torch.cuda.stream(self.stream):
while not self.end_flag:
if self.async_train_queue.empty() or self.cuda_queue.full():
time.sleep(0.01)
else:
data = self.async_train_queue.get()
data = to_device(data, self.device)
self.cuda_queue.put(data)
# If ``self.end_flag``` is True, clear and close async_train_queue,
# because _cuda_loop gets data from async_train_queue.
while not self.async_train_queue.empty():
_ = self.async_train_queue.get()
self.async_train_queue.close()
self.async_train_queue.join_thread()
[docs] def __next__(self) -> Any:
"""
Overview:
Return next data in the iterator. If use cuda, get from ``self.cuda_queue``;
Otherwise, get from ``self.async_train_queue``.
Returns:
- data (:obj:`torch.Tensor`): Next data in the dataloader iterator.
"""
while not self.end_flag:
if self.use_cuda:
if self.cuda_queue.empty():
time.sleep(0.01)
else:
return self.cuda_queue.get()
else:
if self.async_train_queue.empty():
time.sleep(0.01)
else:
return self.async_train_queue.get()
# If ``self.end_flag``` is True, clear and close either 1) or 2):
# 1) cuda_queue. Because user get data from cuda_queue, and async_train_queue is closed by cuda_loop.
# 2) async_train_queue. Because user get data from async_train_queue.
if self.use_cuda:
while not self.cuda_queue.empty():
_ = self.cuda_queue.get()
self.cuda_queue.task_done()
self.cuda_queue.join()
else:
while not self.async_train_queue.empty():
_ = self.async_train_queue.get()
self.async_train_queue.close()
self.async_train_queue.join_thread()
def __del__(self) -> None:
self.close()
[docs] def close(self) -> None:
"""
Overview:
Delete this dataloader. First set ``end_flag`` to True, which means different processes/threads
will clear and close all data queues; Then all processes will be terminated and joined.
"""
if self.end_flag:
return
self.end_flag = True
self.async_process.terminate()
self.async_process.join()
if self.num_workers > 1:
for w in self.worker:
w.terminate()
w.join()
print('Del AsyncDataLoader')