# composer.core.event#

Training Loop Events.

Classes

 Event Enum to represent training loop events.
class composer.core.event.Event(value)[source]#

Enum to represent training loop events.

Events mark specific points in the training loop where an Algorithm and Callback can run.

The following pseudocode shows where each event fires in the training loop:

# <INIT>
# <FIT_START>
for epoch in range(NUM_EPOCHS):
# <EPOCH_START>

# <BATCH_START>

# <BEFORE_TRAIN_BATCH>

# <BEFORE_FORWARD>
outputs = model(batch)
# <AFTER_FORWARD>

# <BEFORE_LOSS>
loss = model.loss(outputs, batch)
# <AFTER_LOSS>

# <BEFORE_BACKWARD>
loss.backward()
# <AFTER_BACKWARD>

# <AFTER_TRAIN_BATCH>
optimizer.step()

# <BATCH_END>

if should_eval(batch=True):
# <EVAL_START>
# <EVAL_BATCH_START>
# <EVAL_BEFORE_FORWARD>
outputs, targets = model(batch)
# <EVAL_AFTER_FORWARD>
metrics.update(outputs, targets)
# <EVAL_BATCH_END>
# <EVAL_END>

# <BATCH_CHECKPOINT>
# <EPOCH_END>

if should_eval(batch=False):
# <EVAL_START>
# <EVAL_BATCH_START>
# <EVAL_BEFORE_FORWARD>
outputs, targets = model(batch)
# <EVAL_AFTER_FORWARD>
metrics.update(outputs, targets)
# <EVAL_BATCH_END>
# <EVAL_END>

# <EPOCH_CHECKPOINT>
# <FIT_END>

INIT#

Invoked in the constructor of Trainer. Model surgery (see module_surgery) typically occurs here.

FIT_START#

Invoked at the beginning of each call to Trainer.fit(). Dataset transformations typically occur here.

EPOCH_START#

Start of an epoch.

Immediately after the dataloader is called. Typically used for on-GPU dataloader transforms.

BATCH_START#

Start of a batch.

BEFORE_TRAIN_BATCH#

Before the forward-loss-backward computation for a training batch. When using gradient accumulation, this is still called only once.

BEFORE_FORWARD#

Before the call to model.forward(). This is called multiple times per batch when using gradient accumulation.

AFTER_FORWARD#

After the call to model.forward(). This is called multiple times per batch when using gradient accumulation.

BEFORE_LOSS#

Before the call to model.loss(). This is called multiple times per batch when using gradient accumulation.

AFTER_LOSS#

After the call to model.loss(). This is called multiple times per batch when using gradient accumulation.

BEFORE_BACKWARD#

Before the call to loss.backward(). This is called multiple times per batch when using gradient accumulation.

AFTER_BACKWARD#

After the call to loss.backward(). This is called multiple times per batch when using gradient accumulation.

AFTER_TRAIN_BATCH#

After the forward-loss-backward computation for a training batch. When using gradient accumulation, this event still fires only once.

BATCH_END#

End of a batch, which occurs after the optimizer step and any gradient scaling.

BATCH_CHECKPOINT#

After Event.BATCH_END and any batch-wise evaluation. Saving checkpoints at this event allows the checkpoint saver to use the results from any batch-wise evaluation to determine whether a checkpoint should be saved.

EPOCH_END#

End of an epoch.

EPOCH_CHECKPOINT#

After Event.EPOCH_END and any epoch-wise evaluation. Saving checkpoints at this event allows event allows the checkpoint saver to use the results from any epoch-wise evaluation to determine whether a checkpointshould be saved.

FIT_END#

Invoked at the end of each call to Trainer.fit(). This event exists primarily for logging information and flushing callbacks. Algorithms should not transform the training state on this event, as any changes will not be preserved in checkpoints.

EVAL_START#

Start of evaluation through the validation dataset.

EVAL_BATCH_START#

Before the call to model.validate(batch)

EVAL_BEFORE_FORWARD#

Before the call to model.validate(batch)

EVAL_AFTER_FORWARD#

After the call to model.validate(batch)

EVAL_BATCH_END#

After the call to model.validate(batch)

EVAL_END#

End of evaluation through the validation dataset.

property canonical_name[source]#

The name of the event, without before/after markers.

Events that have a corresponding “before” or “after” event share the same canonical name.

Example

>>> Event.EPOCH_START.canonical_name
'epoch'
>>> Event.EPOCH_END.canonical_name
'epoch'

Returns

str – The canonical name of the event.

property is_after_event[source]#

Whether the event is an “after” event.

An “after” event (e.g., AFTER_LOSS) has a corresponding “before” event (.e.g., BEFORE_LOSS).

property is_before_event[source]#

Whether the event is an “before” event.

An “before” event (e.g., BEFORE_LOSS) has a corresponding “after” event (.e.g., AFTER_LOSS).