# SeqLengthWarmup#

class composer.algorithms.SeqLengthWarmup(duration=0.3, min_seq_length=8, max_seq_length=1024, step_size=8, truncate=True, preserve_end_of_sequence=False)[source]#

Progressively increases the sequence length during training.

Changes the sequence length of all tensors in the input batch. The sequence length increases from min_seq_length to max_seq_length in steps of step_size during the first duration fraction of training.

The sequence length is then kept at max_seq_length for the rest of training.

Tensors are either truncated (truncate=True) or reshaped to create new examples from the extra tokens (truncate=False).

This algorithm runs on Event.AFTER_DATALOADER to modify the sequence length of a batch of data after the model and data have been moved to accelerators.

Note

step_size should be a multiple of eight for optimal throughput on NVIDIA GPUs.

Note

Variable input lengths can create CUDA OOM errors. To avoid this, we follow the PyTorch notes and pre-allocate the memory with a blank forward and backward pass.

See the Method Card for more details.

Example:

from composer.algorithms import SeqLengthWarmup
from composer import Trainer

seq_length_warmup = SeqLengthWarmup(duration=0.5,
min_seq_length=8,
max_seq_length=1024,
step_size=8,
truncate=True,
preserve_end_of_sequence=False)

trainer = Trainer(model=model,
max_duration="1ep",
algorithms=[seq_length_warmup])

Parameters
• duration (float, optional) – Fraction of total training for sequential length learning. Default = 0.3.

• min_seq_length (int, optional) – Minimum sequence length to start the warmup. Default = 8.

• max_seq_length (int, optional) – Maximum sequence length to stop the warmup. Default = 1024.

• step_size (int, optional) – Step size of sequence length. Default = 8.

• truncate (bool, optional) – Truncate sequences early, or reshape tensors to create new examples out of the extra tokens. Default: True.

• preserve_end_of_sequence (bool, optional) – Preserve the end-of-sequence of the batch when truncating. Useful when input formats include a unique end-of-sequence token. Ignored if truncate=False. Default: False. E.g., if batch["input_ids"] is [[10, 11, 12, 13, 14, 15]] and curr_seq_length=3, "input_ids" in the returned batch would be [[10, 11, 12]] with preserve_end_of_sequence=False and would be [[10, 11, 15]] with preserve_end_of_sequence=True. This behavior applies to any batch tensor with 2 or more dimensions.