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Source code for ignite.engine.engine

import inspect
import logging
import sys
import time
from collections import defaultdict
from enum import Enum

from ignite._utils import _to_hours_mins_secs

IS_PYTHON2 = sys.version_info[0] < 3


[docs]class Events(Enum): """Events that are fired by the :class:`ignite.engine.Engine` during execution""" EPOCH_STARTED = "epoch_started" EPOCH_COMPLETED = "epoch_completed" STARTED = "started" COMPLETED = "completed" ITERATION_STARTED = "iteration_started" ITERATION_COMPLETED = "iteration_completed" EXCEPTION_RAISED = "exception_raised"
[docs]class State(object): """An object that is used to pass internal and user-defined state between event handlers""" def __init__(self, **kwargs): self.iteration = 0 self.output = None self.batch = None for k, v in kwargs.items(): setattr(self, k, v)
[docs]class Engine(object): """Runs a given process_function over each batch of a dataset, emitting events as it goes. Args: process_function (Callable): A function receiving a handle to the engine and the current batch in each iteration, and returns data to be stored in the engine's state Example usage: .. code-block:: python def train_and_store_loss(engine, batch): inputs, targets = batch optimizer.zero_grad() outputs = model(inputs) loss = loss_fn(outputs, targets) loss.backward() optimizer.step() return loss.item() engine = Engine(train_and_store_loss) engine.run(data_loader) # Loss value is now stored in `engine.state.output`. """ def __init__(self, process_function): self._event_handlers = defaultdict(list) self._logger = logging.getLogger(__name__ + "." + self.__class__.__name__) self._logger.addHandler(logging.NullHandler()) self._process_function = process_function self.should_terminate = False self.state = None if self._process_function is None: raise ValueError("Engine must be given a processing function in order to run") self._check_signature(process_function, 'process_function', None)
[docs] def add_event_handler(self, event_name, handler, *args, **kwargs): """Add an event handler to be executed when the specified event is fired Args: event_name (Events): event from ignite.engine.Events to attach the handler to handler (Callable): the callable event handler that should be invoked *args: optional args to be passed to `handler` **kwargs: optional keyword args to be passed to `handler` Notes: The handler function's first argument will be `self`, the `Engine` object it was bound to. Note that other arguments can be passed to the handler in addition to the `*args` and `**kwargs` passed here, for example during `Events.EXCEPTION_RAISED`. Example usage: .. code-block:: python engine = Engine(process_function) def print_epoch(engine): print("Epoch: {}".format(engine.state.epoch)) engine.add_event_handler(Events.EPOCH_COMPLETED, print_epoch) """ if event_name not in Events.__members__.values(): self._logger.error("attempt to add event handler to an invalid event %s ", event_name) raise ValueError("Event {} is not a valid event for this Engine".format(event_name)) event_args = (Exception(), ) if event_name == Events.EXCEPTION_RAISED else () self._check_signature(handler, 'handler', *(event_args + args), **kwargs) self._event_handlers[event_name].append((handler, args, kwargs)) self._logger.debug("added handler for event %s ", event_name)
def _check_signature(self, fn, fn_description, *args, **kwargs): exception_msg = None if IS_PYTHON2: try: callable_ = fn if hasattr(fn, '__name__') else fn.__call__ inspect.getcallargs(callable_, self, *args, **kwargs) except TypeError as exc: spec = inspect.getargspec(callable_) fn_params = list(spec.args) exception_msg = str(exc) else: signature = inspect.signature(fn) try: signature.bind(self, *args, **kwargs) except TypeError as exc: fn_params = list(signature.parameters) exception_msg = str(exc) if exception_msg: passed_params = [self] + list(args) + list(kwargs) raise ValueError("Error adding {} '{}': " "takes parameters {} but will be called with {} " "({})".format( fn, fn_description, fn_params, passed_params, exception_msg))
[docs] def on(self, event_name, *args, **kwargs): """Decorator shortcut for add_event_handler Args: event_name (Events): event to attach the handler to *args: optional args to be passed to `handler` **kwargs: optional keyword args to be passed to `handler` """ def decorator(f): self.add_event_handler(event_name, f, *args, **kwargs) return f return decorator
def _fire_event(self, event_name, *event_args): if event_name in self._event_handlers.keys(): self._logger.debug("firing handlers for event %s ", event_name) for func, args, kwargs in self._event_handlers[event_name]: func(self, *(event_args + args), **kwargs)
[docs] def terminate(self): """Sends terminate signal to the engine, so that it terminates after the current iteration """ self._logger.info("Terminate signaled. Engine will stop after current iteration is finished") self.should_terminate = True
def _run_once_on_dataset(self): start_time = time.time() try: for batch in self.state.dataloader: self.state.batch = batch self.state.iteration += 1 self._fire_event(Events.ITERATION_STARTED) self.state.output = self._process_function(self, batch) self._fire_event(Events.ITERATION_COMPLETED) if self.should_terminate: break except BaseException as e: self._logger.error("Current run is terminating due to exception: %s", str(e)) self._handle_exception(e) time_taken = time.time() - start_time hours, mins, secs = _to_hours_mins_secs(time_taken) return hours, mins, secs def _handle_exception(self, e): if Events.EXCEPTION_RAISED in self._event_handlers: self._fire_event(Events.EXCEPTION_RAISED, e) else: raise e
[docs] def run(self, data, max_epochs=1): """Runs the process_function over the passed data. Args: data (Iterable): Collection of batches allowing repeated iteration (e.g., list or DataLoader) max_epochs (int, optional): max epochs to run for (default: 1) Returns: State: output state """ self.state = State(dataloader=data, epoch=0, max_epochs=max_epochs, metrics={}) try: self._logger.info("Engine run starting with max_epochs={}".format(max_epochs)) start_time = time.time() self._fire_event(Events.STARTED) while self.state.epoch < max_epochs and not self.should_terminate: self.state.epoch += 1 self._fire_event(Events.EPOCH_STARTED) hours, mins, secs = self._run_once_on_dataset() self._logger.info("Epoch[%s] Complete. Time taken: %02d:%02d:%02d", self.state.epoch, hours, mins, secs) if self.should_terminate: break self._fire_event(Events.EPOCH_COMPLETED) self._fire_event(Events.COMPLETED) time_taken = time.time() - start_time hours, mins, secs = _to_hours_mins_secs(time_taken) self._logger.info("Engine run complete. Time taken %02d:%02d:%02d" % (hours, mins, secs)) except BaseException as e: self._logger.error("Engine run is terminating due to exception: %s", str(e)) self._handle_exception(e) return self.state

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