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import torch
from torch import nn
from torch.nn import CrossEntropyLoss
from transformers.models.mamba.modeling_mamba import (
MambaPreTrainedModel,
MambaModel,
MambaCache,
MAMBA_INPUTS_DOCSTRING,
MAMBA_START_DOCSTRING,
)
from typing import List, Optional, Tuple, Union
from transformers.utils import (
ModelOutput,
add_start_docstrings,
add_start_docstrings_to_model_forward,
add_code_sample_docstrings,
)
from dataclasses import dataclass
_CHECKPOINT_FOR_DOC = "state-spaces/mamba-130m-hf"
_CONFIG_FOR_DOC = "MambaConfig"
@dataclass
class MambaSequenceClassifierOutput(ModelOutput):
"""
Base class for outputs of sentence classification models.
Args:
loss (`torch.FloatTensor` of shape `(1,)`, *optional*, returned when `labels` is provided):
Classification (or regression if config.num_labels==1) loss.
logits (`torch.FloatTensor` of shape `(batch_size, config.num_labels)`):
Classification (or regression if config.num_labels==1) scores (before SoftMax).
cache_params (list of five `torch.FloatTensor` of shape `(batch_size, hidden_size, num_hidden_layers)`):
The state of the model at the last time step. Can be used in a forward method with the next `input_ids` to
avoid providing the old `input_ids`.
hidden_states (`tuple(torch.FloatTensor)`, *optional*, returned when `output_hidden_states=True` is passed or when `config.output_hidden_states=True`):
Tuple of `torch.FloatTensor` (one for the output of the embeddings, if the model has an embedding layer, +
one for the output of each layer) of shape `(batch_size, sequence_length, hidden_size)`.
Hidden-states of the model at the output of each layer plus the optional initial embedding outputs.
"""
loss: Optional[torch.FloatTensor] = None
logits: torch.FloatTensor = None
cache_params: Optional[List[torch.FloatTensor]] = None
hidden_states: Optional[Tuple[torch.FloatTensor, ...]] = None
class MambaClassificationHead(nn.Module):
"""Head for sentence-level classification tasks."""
def __init__(self, config):
super().__init__()
self.out_proj = nn.Linear(config.hidden_size, config.num_labels, bias=False)
self.out_proj.weight.data.normal_(mean=0.0, std=config.initializer_range)
self.config = config
def forward(self, features, **kwargs):
x = features
x = self.out_proj(x)
return x
@add_start_docstrings(
"""Mamba Model backbone with a sequence classification/regression head on top (a linear layer on top of
the pooled output) e.g. for GLUE tasks.""",
MAMBA_START_DOCSTRING,
)
class MambaForSequenceClassification(MambaPreTrainedModel):
def __init__(self, config):
super().__init__(config)
self.num_labels = config.num_labels
self.backbone = MambaModel(config)
self.classifier = MambaClassificationHead(config)
# Initialize weights and apply final processing
self.post_init()
@add_start_docstrings_to_model_forward(
MAMBA_INPUTS_DOCSTRING.format("batch_size, sequence_length")
)
@add_code_sample_docstrings(
checkpoint=_CHECKPOINT_FOR_DOC,
output_type=MambaSequenceClassifierOutput,
config_class=_CONFIG_FOR_DOC,
)
def forward(
self,
input_ids: Optional[torch.LongTensor] = None,
inputs_embeds: Optional[torch.FloatTensor] = None,
cache_params: Optional[MambaCache] = None,
use_cache: Optional[bool] = None,
labels: Optional[torch.LongTensor] = None,
output_hidden_states: Optional[bool] = None,
return_dict: Optional[bool] = None,
**kwargs,
) -> Union[Tuple, MambaSequenceClassifierOutput]:
r"""
labels (`torch.LongTensor` of shape `(batch_size,)`, *optional*):
Labels for computing the sequence classification/regression loss.
Indices should be in `[0, ..., config.num_labels - 1]`.
If `config.num_labels == 1` a regression loss is computed (Mean-Square loss),
If `config.num_labels > 1` a classification loss is computed (Cross-Entropy).
"""
return_dict = (
return_dict if return_dict is not None else self.config.use_return_dict
)
mamba_outputs = self.backbone(
input_ids,
cache_params=cache_params,
use_cache=use_cache,
inputs_embeds=inputs_embeds,
output_hidden_states=output_hidden_states,
return_dict=return_dict,
)
hidden_states = mamba_outputs[0]
logits = self.classifier(hidden_states)
if input_ids is not None:
batch_size, sequence_length = input_ids.shape[:2]
else:
batch_size, sequence_length = inputs_embeds.shape[:2]
assert (
self.config.pad_token_id is not None or batch_size == 1
), "Cannot handle batch sizes > 1 if no padding token is defined."
if self.config.pad_token_id is None:
sequence_lengths = -1
else:
if input_ids is not None:
# if no pad token found, use modulo instead of reverse indexing for ONNX compatibility
sequence_lengths = (
torch.eq(input_ids, self.config.pad_token_id).int().argmax(-1) - 1
)
sequence_lengths = sequence_lengths % input_ids.shape[-1]
sequence_lengths = sequence_lengths.to(logits.device)
else:
sequence_lengths = -1
print(
f"{self.__class__.__name__} will not detect padding tokens in `inputs_embeds`. Results may be "
"unexpected if using padding tokens in conjunction with `inputs_embeds.`"
)
pooled_logits = logits[
torch.arange(batch_size, device=logits.device), sequence_lengths
]
loss_fct = CrossEntropyLoss()
loss = loss_fct(pooled_logits.view(-1, self.num_labels), labels.view(-1))
if not return_dict:
output = (pooled_logits,) + mamba_outputs[1:]
return ((loss,) + output) if loss is not None else output
return MambaSequenceClassifierOutput(
loss=loss,
logits=pooled_logits,
cache_params=mamba_outputs.cache_params,
hidden_states=mamba_outputs.hidden_states,
)
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