falcon-40b-instruct / modeling_falcon.py

Move to in-library model (for real this time) (#86)

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	# coding=utf-8
	# Copyright 2023 the Falcon authors and HuggingFace Inc. team. All rights reserved.
	#
	# Licensed under the Apache License, Version 2.0 (the "License");
	# you may not use this file except in compliance with the License.
	# You may obtain a copy of the License at
	#
	# http://www.apache.org/licenses/LICENSE-2.0
	#
	# Unless required by applicable law or agreed to in writing, software
	# distributed under the License is distributed on an "AS IS" BASIS,
	# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	# See the License for the specific language governing permissions and
	# limitations under the License.
	"""PyTorch Falcon model."""

	import math
	from typing import Optional, Tuple, Union

	import torch
	import torch.utils.checkpoint
	from torch import nn
	from torch.nn import BCEWithLogitsLoss, CrossEntropyLoss, LayerNorm, MSELoss
	from torch.nn import functional as F

	from transformers.modeling_outputs import (
	BaseModelOutputWithPastAndCrossAttentions,
	CausalLMOutputWithCrossAttentions,
	QuestionAnsweringModelOutput,
	SequenceClassifierOutputWithPast,
	TokenClassifierOutput,
	)
	from transformers.modeling_utils import PreTrainedModel
	from transformers.utils import add_code_sample_docstrings, add_start_docstrings, add_start_docstrings_to_model_forward, logging
	from .configuration_falcon import FalconConfig


	logger = logging.get_logger(__name__)

	FALCON_PRETRAINED_MODEL_ARCHIVE_LIST = [
	"tiiuae/falcon-40b",
	"tiiuae/falcon-40b-instruct",
	"tiiuae/falcon-7b",
	"tiiuae/falcon-7b-instruct",
	"tiiuae/falcon-rw-7b",
	"tiiuae/falcon-rw-1b",
	]
	_CHECKPOINT_FOR_DOC = "Rocketknight1/falcon-rw-1b"
	_CONFIG_FOR_DOC = "FalconConfig"


	# NOTE(Hesslow): Unfortunately we did not fuse matmul and bias during training, this means that there's one additional quantization to bfloat16 between the operations.
	# In order not to degrade the quality of our HF-port, we keep these characteristics in the final model.
	class FalconLinear(nn.Linear):
	def forward(self, input: torch.Tensor) -> torch.Tensor:
	hidden_states = input @ self.weight.T
	if self.bias is None:
	return hidden_states
	return hidden_states + self.bias


	# rotary pos emb helpers (torch.jit.script does not seem to support staticmethod...)
	def rotate_half(x):
	x1, x2 = x[..., : x.shape[-1] // 2], x[..., x.shape[-1] // 2 :]
	return torch.cat((-x2, x1), dim=-1)


	class FalconRotaryEmbedding(nn.Module):
	"""Implementation of RotaryEmbedding from GPT-NeoX.
	This implementation is designed to operate on queries and keys that are compatible with `[batch_size,
	n_heads_per_partition, seq_len, head_dim]` (e.g. MinGPTAttention format).
	"""

	def __init__(self, head_dim: int, base=10000):
	super().__init__()
	inv_freq = 1.0 / (base ** (torch.arange(0, head_dim, 2).float() / head_dim))
	self.register_buffer("inv_freq", inv_freq, persistent=False)
	self.head_dim = head_dim
	self.seq_len_cached = -1
	self.cos_cached: torch.Tensor \| None = None
	self.sin_cached: torch.Tensor \| None = None

	def cos_sin(self, seq_len: int, past_key_values_length: int, device="cpu", dtype=torch.bfloat16) -> torch.Tensor:
	total_length = seq_len + past_key_values_length
	if total_length > self.seq_len_cached:
	self.seq_len_cached = total_length
	t = torch.arange(total_length, device=device, dtype=self.inv_freq.dtype)
	freqs = torch.einsum("i,j->ij", t, self.inv_freq)
	emb = torch.cat((freqs, freqs), dim=-1).to(device)

	if dtype in [torch.float16, torch.bfloat16]:
	emb = emb.float()

	self.cos_cached = emb.cos()[None, :, :]
	self.sin_cached = emb.sin()[None, :, :]

	self.cos_cached = self.cos_cached.type(dtype)
	self.sin_cached = self.sin_cached.type(dtype)

	return (
	self.cos_cached[:, past_key_values_length : seq_len + past_key_values_length],
	self.sin_cached[:, past_key_values_length : seq_len + past_key_values_length],
	)

	def forward(self, query, key, past_key_values_length=0):
	batch, seq_len, head_dim = query.shape
	cos, sin = self.cos_sin(seq_len, past_key_values_length, query.device, query.dtype)
	return (query * cos) + (rotate_half(query) * sin), (key * cos) + (rotate_half(key) * sin)


	def _make_causal_mask(
	input_ids_shape: torch.Size, device: torch.device, past_key_values_length: int
	) -> torch.BoolTensor:
	"""
	Make causal mask used for self-attention. This mask does not take the existing attention mask into account - it
	just blocks tokens from attending forwards in the sequence. The output shape will be `[batch_size, 1,
	target_length, target_length+past_key_values_length]`.
	"""
	batch_size, target_length = input_ids_shape

	mask = torch.triu(torch.ones((target_length, target_length), dtype=torch.bool, device=device), diagonal=1)
	# If past_key_values_length is 0 this is an empty tensor and the concatenation is a no-op.
	# This code style is an unfortunate consequence of getting your TF engineer to port models; doing it this
	# way avoids a data-dependent conditional, which will help me when I have to port this to XLA later.
	past_mask = torch.zeros((target_length, past_key_values_length), dtype=torch.bool, device=device)
	mask = torch.cat([past_mask, mask], dim=-1)
	expanded_mask = mask[None, None, :, :].expand(batch_size, 1, target_length, target_length + past_key_values_length)
	return expanded_mask


	def _expand_mask(mask: torch.Tensor, past_key_values_length: int) -> torch.BoolTensor:
	"""
	Expands attention_mask from `[batch_size, seq_length]` to `[batch_size, 1, seq_length, seq_length + past_length]`.
	"""
	batch_size, total_length = mask.shape
	seq_length = total_length - past_key_values_length if past_key_values_length is not None else total_length

	expanded_mask = ~(mask[:, None, None, :].to(torch.bool))
	return expanded_mask.expand(batch_size, 1, seq_length, total_length)


	def build_alibi_tensor(attention_mask: torch.Tensor, num_heads: int, dtype: torch.dtype) -> torch.Tensor:
	batch_size, seq_length = attention_mask.shape
	closest_power_of_2 = 2 ** math.floor(math.log2(num_heads))
	base = torch.tensor(
	2 (-(2 -(math.log2(closest_power_of_2) - 3))), device=attention_mask.device, dtype=torch.float32
	)
	powers = torch.arange(1, 1 + closest_power_of_2, device=attention_mask.device, dtype=torch.int32)
	slopes = torch.pow(base, powers)

	if closest_power_of_2 != num_heads:
	extra_base = torch.tensor(
	2 (-(2 -(math.log2(2 * closest_power_of_2) - 3))), device=attention_mask.device, dtype=torch.float32
	)
	num_remaining_heads = min(closest_power_of_2, num_heads - closest_power_of_2)
	extra_powers = torch.arange(1, 1 + 2 * num_remaining_heads, 2, device=attention_mask.device, dtype=torch.int32)
	slopes = torch.cat([slopes, torch.pow(extra_base, extra_powers)], dim=0)

	# Note: alibi will added to the attention bias that will be applied to the query, key product of attention
	# => therefore alibi will have to be of shape (batch_size, num_heads, query_length, key_length)
	# => here we set (batch_size=1, num_heads=num_heads, query_length=1, key_length=max_length)
	# => the query_length dimension will then be broadcasted correctly
	# This is more or less identical to T5's relative position bias:
	# https://github.com/huggingface/transformers/blob/f681437203baa7671de3174b0fa583c349d9d5e1/src/transformers/models/t5/modeling_t5.py#L527
	arange_tensor = ((attention_mask.cumsum(dim=-1) - 1) * attention_mask)[:, None, :]
	alibi = slopes[..., None].bfloat16() * arange_tensor
	return alibi.reshape(batch_size * num_heads, 1, seq_length).to(dtype)


	# Copied from transformers.models.bloom.modeling_bloom.dropout_add
	def dropout_add(x: torch.Tensor, residual: torch.Tensor, prob: float, training: bool) -> torch.Tensor:
	"""
	Dropout add function

	Args:
	x (`torch.tensor`, required):
	input tensor
	residual (`torch.tensor`, required):
	residual tensor
	prob (`float`, required):
	dropout probability
	training (`bool`, required):
	training mode
	"""
	out = F.dropout(x, p=prob, training=training)
	out = residual + out
	return out


	class FalconAttention(nn.Module):
	def __init__(self, config: FalconConfig):
	super().__init__()

	self.hidden_size = config.hidden_size
	self.num_heads = config.num_attention_heads
	self.head_dim = self.hidden_size // self.num_heads
	self.split_size = self.hidden_size
	self.hidden_dropout = config.hidden_dropout

	if self.head_dim * self.num_heads != self.hidden_size:
	raise ValueError(
	f"`hidden_size` must be divisible by num_heads (got `hidden_size`: {self.hidden_size} and `num_heads`:"
	f" {self.num_heads})."
	)

	self.maybe_rotary = FalconRotaryEmbedding(config.head_dim) if config.rotary else lambda q, k, t: (q, k)

	# Layer-wise attention scaling
	self.inv_norm_factor = 1.0 / math.sqrt(self.head_dim)
	self.beta = self.inv_norm_factor
	if config.new_decoder_architecture:
	qkv_out_dim = (config.num_kv_heads * 2 + config.num_attention_heads) * self.head_dim
	elif config.multi_query:
	qkv_out_dim = self.hidden_size + 2 * self.head_dim
	else:
	qkv_out_dim = 3 * self.hidden_size
	self.query_key_value = FalconLinear(self.hidden_size, qkv_out_dim, bias=config.bias)
	self.new_decoder_architecture = config.new_decoder_architecture
	self.multi_query = config.multi_query
	self.dense = FalconLinear(self.hidden_size, self.hidden_size, bias=config.bias)
	self.attention_dropout = nn.Dropout(config.attention_dropout)
	self.num_kv_heads = config.num_kv_heads if (self.new_decoder_architecture or not self.multi_query) else 1

	def _split_heads(self, fused_qkv: torch.Tensor) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
	"""
	Split the last dimension into (num_heads, head_dim), results share same memory storage as `fused_qkv`

	Args:
	fused_qkv (`torch.tensor`, required): [batch_size, seq_length, num_heads * 3 * head_dim]

	Returns:
	query: [batch_size, seq_length, num_heads, head_dim] key: [batch_size, seq_length, num_heads, head_dim]
	value: [batch_size, seq_length, num_heads, head_dim]
	"""
	if self.new_decoder_architecture:
	batch, seq_len, _ = fused_qkv.shape
	qkv = fused_qkv.view(batch, seq_len, -1, self.num_heads // self.num_kv_heads + 2, self.head_dim)
	query = qkv[:, :, :, :-2]
	key = qkv[:, :, :, [-2]]
	value = qkv[:, :, :, [-1]]
	key = torch.broadcast_to(key, query.shape)
	value = torch.broadcast_to(value, query.shape)

	query, key, value = [x.flatten(2, 3) for x in (query, key, value)]
	return query, key, value
	elif not self.multi_query:
	batch_size, seq_length, three_times_hidden_size = fused_qkv.shape
	fused_qkv = fused_qkv.view(batch_size, seq_length, self.num_heads, 3, self.head_dim)
	return fused_qkv[..., 0, :], fused_qkv[..., 1, :], fused_qkv[..., 2, :]
	else:
	batch_size, seq_length, three_times_hidden_size = fused_qkv.shape
	fused_qkv = fused_qkv.view(batch_size, seq_length, self.num_heads + 2, self.head_dim)
	return fused_qkv[..., :-2, :], fused_qkv[..., [-2], :], fused_qkv[..., [-1], :]

	# Copied from transformers.models.bloom.modeling_bloom.BloomAttention._merge_heads
	def _merge_heads(self, x: torch.Tensor) -> torch.Tensor:
	"""
	Merge heads together over the last dimenstion

	Args:
	x (`torch.tensor`, required): [batch_size * num_heads, seq_length, head_dim]

	Returns:
	torch.tensor: [batch_size, seq_length, num_heads * head_dim]
	"""
	# What we want to achieve is:
	# batch_size * num_heads, seq_length, head_dim -> batch_size, seq_length, num_heads * head_dim
	batch_size_and_num_heads, seq_length, _ = x.shape
	batch_size = batch_size_and_num_heads // self.num_heads

	# First view to decompose the batch size
	# batch_size * num_heads, seq_length, head_dim -> batch_size, num_heads, seq_length, head_dim
	x = x.view(batch_size, self.num_heads, seq_length, self.head_dim)

	# batch_size, num_heads, seq_length, head_dim -> batch_size, seq_length, num_heads, head_dim
	x = x.permute(0, 2, 1, 3)

	# batch_size, seq_length, num_heads, head_dim -> batch_size, seq_length, num_heads * head_dim
	return x.reshape(batch_size, seq_length, self.num_heads * self.head_dim)

	def forward(
	self,
	hidden_states: torch.Tensor,
	alibi: Optional[torch.Tensor],
	attention_mask: torch.Tensor,
	layer_past: Optional[Tuple[torch.Tensor, torch.Tensor]] = None,
	head_mask: Optional[torch.Tensor] = None,
	use_cache: bool = False,
	output_attentions: bool = False,
	):
	fused_qkv = self.query_key_value(hidden_states) # [batch_size, seq_length, 3 x hidden_size]
	num_kv_heads = self.num_heads if self.new_decoder_architecture else self.num_kv_heads
	# 3 x [batch_size, seq_length, num_heads, head_dim]
	(query_layer, key_layer, value_layer) = self._split_heads(fused_qkv)

	batch_size, query_length, _, _ = query_layer.shape

	query_layer = query_layer.transpose(1, 2).reshape(batch_size * self.num_heads, query_length, self.head_dim)
	key_layer = key_layer.transpose(1, 2).reshape(
	batch_size * num_kv_heads,
	query_length,
	self.head_dim,
	)
	value_layer = value_layer.transpose(1, 2).reshape(batch_size * num_kv_heads, query_length, self.head_dim)

	past_kv_length = 0 if layer_past is None else layer_past[0].shape[1]
	query_layer, key_layer = self.maybe_rotary(query_layer, key_layer, past_kv_length)

	if layer_past is not None:
	past_key, past_value = layer_past
	# concatenate along seq_length dimension:
	# - key: [batch_size * self.num_heads, kv_length, head_dim]
	# - value: [batch_size * self.num_heads, kv_length, head_dim]
	key_layer = torch.cat((past_key, key_layer), dim=1)
	value_layer = torch.cat((past_value, value_layer), dim=1)

	_, kv_length, _ = key_layer.shape
	if use_cache:
	present = (key_layer, value_layer)
	else:
	present = None

	attention_mask_float = (attention_mask * 1.0).masked_fill(attention_mask, float("-1e9")).to(query_layer.dtype)

	query_layer_ = query_layer.reshape(batch_size, self.num_heads, -1, self.head_dim)
	key_layer_ = key_layer.reshape(batch_size, num_kv_heads, -1, self.head_dim)
	value_layer_ = value_layer.reshape(batch_size, num_kv_heads, -1, self.head_dim)

	if alibi is None:
	if output_attentions:
	# F.scaled_dot_product_attention doesn't return the attention weights, so we have
	# to do it by hand if we want them
	attention_scores = query_layer_ @ key_layer_.transpose(-1, -2)
	attention_scores /= math.sqrt(self.head_dim)

	attention_scores = F.softmax(
	attention_scores + attention_mask_float, dim=-1, dtype=hidden_states.dtype
	)
	attn_output = attention_scores @ value_layer_
	else:
	attn_output = F.scaled_dot_product_attention(
	query_layer_, key_layer_, value_layer_, attention_mask_float, 0.0, is_causal=False
	)
	attention_scores = None

	attn_output = attn_output.view(batch_size, self.num_heads, query_length, self.head_dim)
	attn_output = attn_output.permute(0, 2, 1, 3)
	attn_output = attn_output.reshape(batch_size, query_length, self.num_heads * self.head_dim)

	output_tensor = self.dense(attn_output)

	if output_attentions:
	return output_tensor, present, attention_scores
	else:
	return output_tensor, present

	else:
	matmul_result = query_layer_ @ key_layer_.transpose(-1, -2)

	# change view to [batch_size, num_heads, q_length, kv_length]
	attention_scores = matmul_result.view(batch_size, self.num_heads, query_length, kv_length)

	# cast attention scores to fp32, compute scaled softmax and cast back to initial dtype - [batch_size, num_heads, q_length, kv_length]
	input_dtype = attention_scores.dtype
	# `float16` has a minimum value of -65504.0, whereas `bfloat16` and `float32` have a minimum value of `-3.4e+38`
	if input_dtype == torch.float16 or input_dtype == torch.bfloat16:
	attention_scores = attention_scores.to(torch.float32)
	# Matt (HF) note: We could possibly use F.scaled_dot_product_attention here too, by
	# adding (alibi * self.inv_norm_factor) to attention_mask_float. I think this would be mathematically
	# equivalent and more performant, but there might be a numerical difference. If you're reading this
	# and you'd like to experiment and maybe file a PR, feel free!
	attention_logits = attention_scores + alibi.view(batch_size, self.num_heads, 1, -1)
	attention_logits *= self.inv_norm_factor
	attention_probs = F.softmax(attention_logits + attention_mask_float, dim=-1, dtype=hidden_states.dtype)
	# [batch_size, num_heads, q_length, kv_length]
	attention_probs = self.attention_dropout(attention_probs)

	if head_mask is not None:
	attention_probs = attention_probs * head_mask

	# change view [batch_size, num_heads, q_length, kv_length]
	attention_probs_reshaped = attention_probs.view(batch_size, self.num_heads, query_length, kv_length)

	# matmul: [batch_size * num_heads, q_length, head_dim]
	context_layer = (attention_probs_reshaped @ value_layer_).flatten(0, 1)

	# change view [batch_size, num_heads, q_length, head_dim]
	context_layer = self._merge_heads(context_layer)

	output_tensor = self.dense(context_layer)

	if output_attentions:
	return output_tensor, present, attention_probs
	else:
	return output_tensor, present


	class FalconMLP(nn.Module):
	def __init__(self, config: FalconConfig):
	super().__init__()
	hidden_size = config.hidden_size

	self.dense_h_to_4h = FalconLinear(hidden_size, 4 * hidden_size, bias=config.bias)
	self.act = nn.GELU()
	self.dense_4h_to_h = FalconLinear(4 * hidden_size, hidden_size, bias=config.bias)
	self.hidden_dropout = config.hidden_dropout

	def forward(self, x: torch.Tensor) -> torch.Tensor:
	x = self.act(self.dense_h_to_4h(x))
	x = self.dense_4h_to_h(x)
	return x


	class FalconDecoderLayer(nn.Module):
	def __init__(self, config: FalconConfig):
	super().__init__()
	hidden_size = config.hidden_size
	self.num_heads = config.num_attention_heads
	self.self_attention = FalconAttention(config)
	self.mlp = FalconMLP(config)
	self.hidden_dropout = config.hidden_dropout
	self.config = config

	if config.new_decoder_architecture:
	# The layer norm before self-attention
	self.ln_attn = LayerNorm(hidden_size, eps=config.layer_norm_epsilon)
	# The layer norm before the MLP
	self.ln_mlp = LayerNorm(hidden_size, eps=config.layer_norm_epsilon)
	else:
	self.input_layernorm = LayerNorm(hidden_size, eps=config.layer_norm_epsilon)
	if not config.parallel_attn:
	self.post_attention_layernorm = LayerNorm(hidden_size, eps=config.layer_norm_epsilon)

	def forward(
	self,
	hidden_states: torch.Tensor,
	alibi: Optional[torch.Tensor],
	attention_mask: torch.Tensor,
	layer_past: Optional[Tuple[torch.Tensor, torch.Tensor]] = None,
	head_mask: Optional[torch.Tensor] = None,
	use_cache: bool = False,
	output_attentions: bool = False,
	):
	residual = hidden_states

	if self.config.new_decoder_architecture:
	attention_layernorm_out = self.ln_attn(hidden_states)
	mlp_layernorm_out = self.ln_mlp(hidden_states)
	else:
	attention_layernorm_out = self.input_layernorm(hidden_states)

	# Self attention.
	attn_outputs = self.self_attention(
	attention_layernorm_out,
	layer_past=layer_past,
	attention_mask=attention_mask,
	alibi=alibi,
	head_mask=head_mask,
	use_cache=use_cache,
	output_attentions=output_attentions,
	)

	attention_output = attn_outputs[0]

	if not self.config.new_decoder_architecture:
	if self.config.parallel_attn:
	mlp_layernorm_out = attention_layernorm_out
	else:
	residual = dropout_add(
	attention_output, residual, self.config.attention_dropout, training=self.training
	)
	mlp_layernorm_out = self.post_attention_layernorm(residual)

	outputs = attn_outputs[1:]

	# MLP.
	mlp_output = self.mlp(mlp_layernorm_out)

	if self.config.new_decoder_architecture or self.config.parallel_attn:
	mlp_output += attention_output

	output = dropout_add(mlp_output, residual, self.config.hidden_dropout, training=self.training)

	if use_cache:
	outputs = (output,) + outputs
	else:
	outputs = (output,) + outputs[1:]

	return outputs # hidden_states, present, attentions


	FALCON_START_DOCSTRING = r"""

	This model inherits from [`PreTrainedModel`]. Check the superclass documentation for the generic methods the
	library implements for all its model (such as downloading or saving, resizing the input embeddings etc.)

	This model is also a PyTorch [torch.nn.Module](https://pytorch.org/docs/stable/nn.html#torch.nn.Module) subclass.
	Use it as a regular PyTorch Module and refer to the PyTorch documentation for all matter related to general usage
	and behavior.

	Parameters:
	config ([`FalconConfig`]): Model configuration class with all the parameters of the model.
	Initializing with a config file does not load the weights associated with the model, only the
	configuration. Check out the [`~PreTrainedModel.from_pretrained`] method to load the model weights.
	"""

	FALCON_INPUTS_DOCSTRING = r"""
	Args:
	input_ids (`torch.LongTensor` of shape `(batch_size, input_ids_length)`):
	`input_ids_length` = `sequence_length` if `past_key_values` is `None` else `past_key_values[0][0].shape[2]`
	(`sequence_length` of input past key value states). Indices of input sequence tokens in the vocabulary.

	If `past_key_values` is used, only `input_ids` that do not have their past calculated should be passed as
	`input_ids`.

	Indices can be obtained using [`AutoTokenizer`]. See [`PreTrainedTokenizer.encode`] and
	[`PreTrainedTokenizer.__call__`] for details.

	[What are input IDs?](../glossary#input-ids)
	past_key_values (`Tuple[Tuple[torch.Tensor]]` of length `config.num_hidden_layers`):
	Contains precomputed hidden-states (key and values in the attention blocks) as computed by the model (see
	`past_key_values` output below). Can be used to speed up sequential decoding. The `input_ids` which have
	their past given to this model should not be passed as `input_ids` as they have already been computed.

	Each element of `past_key_values` is a tuple (past_key, past_value):
	- past_key: [batch_size * num_heads, head_dim, kv_length]
	- past_value: [batch_size * num_heads, kv_length, head_dim]
	attention_mask (`torch.FloatTensor` of shape `(batch_size, sequence_length)`, optional):
	Mask to avoid performing attention on padding token indices. Mask values selected in `[0, 1]`:

	- 1 for tokens that are not masked,
	- 0 for tokens that are masked.

	[What are attention masks?](../glossary#attention-mask)
	head_mask (`torch.FloatTensor` of shape `(num_heads,)` or `(num_layers, num_heads)`, optional):
	Mask to nullify selected heads of the self-attention modules. Mask values selected in `[0, 1]`:

	- 1 indicates the head is not masked,
	- 0 indicates the head is masked.

	inputs_embeds (`torch.FloatTensor` of shape `(batch_size, sequence_length, hidden_size)`, optional):
	Optionally, instead of passing `input_ids` you can choose to directly pass an embedded representation. This
	is useful if you want more control over how to convert `input_ids` indices into associated vectors than the
	model's internal embedding lookup matrix.

	If `past_key_values` is used, optionally only the last `inputs_embeds` have to be input (see
	`past_key_values`).
	use_cache (`bool`, optional):
	If set to `True`, `past_key_values` key value states are returned and can be used to speed up decoding (see
	`past_key_values`).
	output_attentions (`bool`, optional):
	Whether or not to return the attentions tensors of all attention layers. See `attentions` under returned
	tensors for more detail.
	output_hidden_states (`bool`, optional):
	Whether or not to return the hidden states of all layers. See `hidden_states` under returned tensors for
	more detail.
	return_dict (`bool`, optional):
	Whether or not to return a [`~file_utils.ModelOutput`] instead of a plain tuple.
	"""


	class FalconPreTrainedModel(PreTrainedModel):
	"""
	An abstract class to handle weights initialization and a simple interface for downloading and loading pretrained
	models.
	"""

	config_class = FalconConfig
	base_model_prefix = "transformer"
	supports_gradient_checkpointing = True
	_no_split_modules = ["FalconDecoderLayer"]

	def __init__(self, inputs, *kwargs):
	super().__init__(inputs, *kwargs)

	def _init_weights(self, module: nn.Module):
	"""Initialize the weights."""
	if isinstance(module, nn.Linear) or isinstance(module, FalconLinear):
	# Slightly different from the TF version which uses truncated_normal for initialization
	# cf https://github.com/pytorch/pytorch/pull/5617
	module.weight.data.normal_(mean=0.0, std=self.config.initializer_range)
	if module.bias is not None:
	module.bias.data.zero_()
	elif isinstance(module, nn.Embedding):
	module.weight.data.normal_(mean=0.0, std=self.config.initializer_range)
	if module.padding_idx is not None:
	module.weight.data[module.padding_idx].zero_()
	elif isinstance(module, LayerNorm):
	module.bias.data.zero_()
	module.weight.data.fill_(1.0)

	# Copied from transformers.models.bloom.modeling_bloom.BloomPreTrainedModel._set_gradient_checkpointing with BloomModel->FalconModel
	def _set_gradient_checkpointing(self, module: nn.Module, value: bool = False):
	if isinstance(module, FalconModel):
	module.gradient_checkpointing = value

	@staticmethod
	def _convert_cache_to_standard_format(
	past_key_value: Tuple[Tuple[torch.Tensor, torch.Tensor]], batch_size: int
	) -> Tuple[Tuple[torch.Tensor, torch.Tensor]]:
	"""
	Standardizes the format of the cache so as to match most implementations, i.e. to tuple(tuple([batch_size,
	num_heads, ...]))
	"""
	batch_size_times_num_heads, kv_length, head_dim = past_key_value[0][0].shape
	# [batch_size * self.num_heads, kv_length, head_dim] -> [batch_size, num_heads, kv_length, head_dim]
	# Note that don't want to use self.num_attention_heads because the number of heads may vary depending
	# on whether we use multi_query attention.
	num_heads = batch_size_times_num_heads // batch_size
	return tuple(
	(
	layer_past[0].view(batch_size, num_heads, kv_length, head_dim),
	layer_past[1].view(batch_size, num_heads, kv_length, head_dim),
	)
	for layer_past in past_key_value
	)

	@staticmethod
	def _convert_to_rw_cache(
	past_key_value: Tuple[Tuple[torch.Tensor, torch.Tensor]]
	) -> Tuple[Tuple[torch.Tensor, torch.Tensor]]:
	batch_size, num_heads, kv_length, head_dim = past_key_value[0][0].shape
	batch_size_times_num_heads = batch_size * num_heads
	# [batch_size, num_heads, kv_length, head_dim] -> [batch_size * num_heads, kv_length, head_dim]
	return tuple(
	(
	layer_past[0].view(batch_size_times_num_heads, kv_length, head_dim),
	layer_past[1].view(batch_size_times_num_heads, kv_length, head_dim),
	)
	for layer_past in past_key_value
	)


	@add_start_docstrings(
	"The bare Falcon Model transformer outputting raw hidden-states without any specific head on top.",
	FALCON_START_DOCSTRING,
	)
	class FalconModel(FalconPreTrainedModel):
	def __init__(self, config: FalconConfig):
	super().__init__(config)

	self.embed_dim = config.hidden_size
	self.num_heads = config.num_attention_heads
	self.use_alibi = config.alibi

	# Embedding + LN Embedding
	self.word_embeddings = nn.Embedding(config.vocab_size, self.embed_dim)

	# Transformer blocks
	self.h = nn.ModuleList([FalconDecoderLayer(config) for _ in range(config.num_hidden_layers)])

	# Final Layer Norm
	self.ln_f = LayerNorm(self.embed_dim, eps=config.layer_norm_epsilon)

	self.gradient_checkpointing = False

	# Initialize weights and apply final processing
	self.post_init()

	def get_input_embeddings(self):
	return self.word_embeddings

	@staticmethod
	def _prepare_attn_mask(
	attention_mask: torch.Tensor, input_shape: Tuple[int, int], past_key_values_length: int
	) -> torch.BoolTensor:
	# Create a causal mask
	# The attention mask we receive as input should cover the whole extended sequence, including any past
	# cache, so its shape should be [batch_size, seq_length + past_key_values_length]
	# The output shape will be [batch_size, 1, seq_length, seq_length + past_key_values_length]
	if input_shape[1] + past_key_values_length != attention_mask.shape[1]:
	raise ValueError(
	"Attention mask shape should be (batch_size, seq_length + past_key_values_length)"
	f" but is {attention_mask.shape} with input_ids shape {input_shape} and past length"
	f" {past_key_values_length}."
	)
	combined_attention_mask = None
	device = attention_mask.device
	_, seq_length = input_shape

	if seq_length > 1:
	combined_attention_mask = _make_causal_mask(
	input_shape, device=device, past_key_values_length=past_key_values_length
	)

	# [batch_size, seq_length + past_key_values_length] -> [batch_size, 1, seq_length, seq_length + past_key_values_length]
	expanded_attn_mask = _expand_mask(attention_mask, past_key_values_length=past_key_values_length)
	combined_attention_mask = (
	expanded_attn_mask if combined_attention_mask is None else expanded_attn_mask \| combined_attention_mask
	)

	return combined_attention_mask

	def set_input_embeddings(self, new_embeddings: torch.Tensor):
	self.word_embeddings = new_embeddings

	@add_start_docstrings_to_model_forward(FALCON_INPUTS_DOCSTRING)
	@add_code_sample_docstrings(
	checkpoint=_CHECKPOINT_FOR_DOC,
	output_type=BaseModelOutputWithPastAndCrossAttentions,
	config_class=_CONFIG_FOR_DOC,
	)
	def forward(
	self,
	input_ids: Optional[torch.LongTensor] = None,
	past_key_values: Optional[Tuple[Tuple[torch.Tensor, torch.Tensor], ...]] = None,
	attention_mask: Optional[torch.Tensor] = None,
	head_mask: Optional[torch.LongTensor] = None,
	inputs_embeds: Optional[torch.LongTensor] = None,
	use_cache: Optional[bool] = None,
	output_attentions: Optional[bool] = None,
	output_hidden_states: Optional[bool] = None,
	return_dict: Optional[bool] = None,
	) -> Union[Tuple[torch.Tensor, ...], BaseModelOutputWithPastAndCrossAttentions]:
	output_attentions = output_attentions if output_attentions is not None else self.config.output_attentions
	output_hidden_states = (
	output_hidden_states if output_hidden_states is not None else self.config.output_hidden_states
	)
	use_cache = use_cache if use_cache is not None else self.config.use_cache
	return_dict = return_dict if return_dict is not None else self.config.use_return_dict

	if input_ids is not None and inputs_embeds is not None:
	raise ValueError("You cannot specify both input_ids and inputs_embeds at the same time")
	elif input_ids is not None:
	batch_size, seq_length = input_ids.shape
	elif inputs_embeds is not None:
	batch_size, seq_length, _ = inputs_embeds.shape
	else:
	raise ValueError("You have to specify either input_ids or inputs_embeds")

	if past_key_values is None:
	past_key_values = tuple([None] * len(self.h))
	else:
	past_key_values = self._convert_to_rw_cache(past_key_values)

	# Prepare head mask if needed
	# 1.0 in head_mask indicate we keep the head
	# attention_probs has shape batch_size x num_heads x N x N
	# head_mask has shape n_layer x batch x num_heads x N x N
	head_mask = self.get_head_mask(head_mask, self.config.num_hidden_layers)

	if inputs_embeds is None:
	inputs_embeds = self.word_embeddings(input_ids)

	hidden_states = inputs_embeds

	presents = () if use_cache else None
	all_self_attentions = () if output_attentions else None
	all_hidden_states = () if output_hidden_states else None

	# Compute alibi tensor: check build_alibi_tensor documentation
	past_key_values_length = 0
	if past_key_values[0] is not None:
	past_key_values_length = past_key_values[0][0].shape[1] # 1 because RW-cache, not standard format
	if attention_mask is None:
	attention_mask = torch.ones((batch_size, seq_length + past_key_values_length), device=hidden_states.device)
	else:
	attention_mask = attention_mask.to(hidden_states.device)

	if self.use_alibi:
	alibi = build_alibi_tensor(attention_mask, self.num_heads, dtype=hidden_states.dtype)
	else:
	alibi = None

	causal_mask = self._prepare_attn_mask(
	attention_mask,
	input_shape=(batch_size, seq_length),
	past_key_values_length=past_key_values_length,
	)

	for i, (block, layer_past) in enumerate(zip(self.h, past_key_values)):
	if output_hidden_states:
	all_hidden_states = all_hidden_states + (hidden_states,)

	if self.gradient_checkpointing and self.training:
	if use_cache:
	logger.warning(
	"`use_cache=True` is incompatible with gradient checkpointing. Setting `use_cache=False`..."
	)
	use_cache = False

	def create_custom_forward(module):
	def custom_forward(*inputs):
	# None for past_key_value
	return module(*inputs, use_cache=use_cache, output_attentions=output_attentions)

	return custom_forward

	outputs = torch.utils.checkpoint.checkpoint(
	create_custom_forward(block),
	hidden_states,
	alibi,
	causal_mask,
	head_mask[i],
	)
	else:
	outputs = block(
	hidden_states,
	layer_past=layer_past,
	attention_mask=causal_mask,
	head_mask=head_mask[i],
	use_cache=use_cache,
	output_attentions=output_attentions,
	alibi=alibi,
	)

	hidden_states = outputs[0]
	if use_cache is True:
	presents = presents + (outputs[1],)

	if output_attentions:
	all_self_attentions = all_self_attentions + (outputs[2 if use_cache else 1],)

	# Add last hidden state
	hidden_states = self.ln_f(hidden_states)

	if output_hidden_states:
	all_hidden_states = all_hidden_states + (hidden_states,)

	if presents is not None:
	presents = self._convert_cache_to_standard_format(presents, batch_size)

	if not return_dict:
	return tuple(v for v in [hidden_states, presents, all_hidden_states, all_self_attentions] if v is not None)

	return BaseModelOutputWithPastAndCrossAttentions(
	last_hidden_state=hidden_states,
	past_key_values=presents,
	hidden_states=all_hidden_states,
	attentions=all_self_attentions,
	)


	@add_start_docstrings(
	"The Falcon Model transformer with a language modeling head on top (linear layer with weights tied to the input embeddings).",
	FALCON_START_DOCSTRING,
	)
	class FalconForCausalLM(FalconPreTrainedModel):
	_tied_weights_keys = ["lm_head.weight"]

	def __init__(self, config: FalconConfig):
	super().__init__(config)
	self.transformer = FalconModel(config)
	self.lm_head = nn.Linear(config.hidden_size, config.vocab_size, bias=False)

	# Initialize weights and apply final processing
	self.post_init()

	def get_output_embeddings(self):
	return self.lm_head

	def set_output_embeddings(self, new_embeddings: torch.Tensor):
	self.lm_head = new_embeddings

	def prepare_inputs_for_generation(
	self,
	input_ids: torch.LongTensor,
	past_key_values: Optional[torch.Tensor] = None,
	attention_mask: Optional[torch.Tensor] = None,
	**kwargs,
	) -> dict:
	if past_key_values is not None:
	input_ids = input_ids[:, -1:]

	return {
	"input_ids": input_ids,
	"past_key_values": past_key_values,
	"use_cache": kwargs.get("use_cache"),
	"attention_mask": attention_mask,
	}

	@add_start_docstrings_to_model_forward(FALCON_INPUTS_DOCSTRING)
	@add_code_sample_docstrings(
	checkpoint=_CHECKPOINT_FOR_DOC,
	output_type=CausalLMOutputWithCrossAttentions,
	config_class=_CONFIG_FOR_DOC,
	)
	def forward(
	self,
	input_ids: Optional[torch.LongTensor] = None,
	past_key_values: Optional[Tuple[Tuple[torch.Tensor, torch.Tensor], ...]] = None,
	attention_mask: Optional[torch.Tensor] = None,
	head_mask: Optional[torch.Tensor] = None,
	inputs_embeds: Optional[torch.Tensor] = None,
	labels: Optional[torch.Tensor] = None,
	use_cache: Optional[bool] = None,
	output_attentions: Optional[bool] = None,
	output_hidden_states: Optional[bool] = None,
	return_dict: Optional[bool] = None,
	) -> Union[Tuple[torch.Tensor], CausalLMOutputWithCrossAttentions]:
	r"""
	labels (`torch.LongTensor` of shape `(batch_size, sequence_length)`, optional):
	Labels for language modeling. Note that the labels are shifted inside the model, i.e. you can set
	`labels = input_ids` Indices are selected in `[-100, 0, ..., config.vocab_size]` All labels set to `-100`
	are ignored (masked), the loss is only computed for labels in `[0, ..., config.vocab_size]`
	"""

	return_dict = return_dict if return_dict is not None else self.config.use_return_dict

	transformer_outputs = self.transformer(
	input_ids,
	past_key_values=past_key_values,
	attention_mask=attention_mask,
	head_mask=head_mask,
	inputs_embeds=inputs_embeds,
	use_cache=use_cache,
	output_attentions=output_attentions,
	output_hidden_states=output_hidden_states,
	return_dict=return_dict,
	)
	hidden_states = transformer_outputs[0]

	lm_logits = self.lm_head(hidden_states)

	loss = None
	if labels is not None:
	# Shift so that tokens < n predict n
	shift_logits = lm_logits[..., :-1, :].contiguous()
	shift_labels = labels[..., 1:].contiguous()
	batch_size, seq_length, vocab_size = shift_logits.shape
	# Flatten the tokens
	loss_fct = CrossEntropyLoss()
	loss = loss_fct(
	shift_logits.view(batch_size * seq_length, vocab_size), shift_labels.view(batch_size * seq_length)
	)

	if not return_dict:
	output = (lm_logits,) + transformer_outputs[1:]
	return ((loss,) + output) if loss is not None else output

	return CausalLMOutputWithCrossAttentions(
	loss=loss,
	logits=lm_logits,
	past_key_values=transformer_outputs.past_key_values,
	hidden_states=transformer_outputs.hidden_states,
	attentions=transformer_outputs.attentions,
	)

	def _reorder_cache(
	self, past: Tuple[Tuple[torch.Tensor, torch.Tensor], ...], beam_idx: torch.LongTensor
	) -> Tuple[Tuple[torch.Tensor, torch.Tensor], ...]:
	"""
	This function is used to re-order the `past_key_values` cache if [`~PreTrainedModel.beam_search`] or
	[`~PreTrainedModel.beam_sample`] is called. This is required to match `past_key_values` with the correct
	beam_idx at every generation step.

	Output shares the same memory storage as `past`.
	"""

	# Get a copy of `beam_idx` on all the devices where we need those indices.
	device_to_beam_idx = {
	past_state.device: beam_idx.to(past_state.device) for layer_past in past for past_state in layer_past
	}
	reordered_past = tuple(
	(
	layer_past[0].index_select(0, device_to_beam_idx[layer_past[0].device]),
	layer_past[1].index_select(0, device_to_beam_idx[layer_past[0].device]),
	)
	for layer_past in past
	)
	return reordered_past


	@add_start_docstrings(
	"""
	The Falcon Model transformer with a sequence classification head on top (linear layer).

	[`FalconForSequenceClassification`] uses the last token in order to do the classification, as other causal models
	(e.g. GPT-1) do.

	Since it does classification on the last token, it requires to know the position of the last token. If a
	`pad_token_id` is defined in the configuration, it finds the last token that is not a padding token in each row. If
	no `pad_token_id` is defined, it simply takes the last value in each row of the batch. Since it cannot guess the
	padding tokens when `inputs_embeds` are passed instead of `input_ids`, it does the same (take the last value in
	each row of the batch).
	""",
	FALCON_START_DOCSTRING,
	)
	class FalconForSequenceClassification(FalconPreTrainedModel):
	def __init__(self, config: FalconConfig):
	super().__init__(config)
	self.num_labels = config.num_labels
	self.transformer = FalconModel(config)
	self.score = nn.Linear(config.hidden_size, config.num_labels, bias=False)

	# Initialize weights and apply final processing
	self.post_init()

	@add_start_docstrings_to_model_forward(FALCON_INPUTS_DOCSTRING)
	@add_code_sample_docstrings(
	checkpoint=_CHECKPOINT_FOR_DOC,
	output_type=SequenceClassifierOutputWithPast,
	config_class=_CONFIG_FOR_DOC,
	)
	def forward(
	self,
	input_ids: Optional[torch.LongTensor] = None,
	past_key_values: Optional[Tuple[Tuple[torch.Tensor, torch.Tensor], ...]] = None,
	attention_mask: Optional[torch.Tensor] = None,
	head_mask: Optional[torch.Tensor] = None,
	inputs_embeds: Optional[torch.Tensor] = None,
	labels: Optional[torch.Tensor] = None,
	use_cache: Optional[bool] = None,
	output_attentions: Optional[bool] = None,
	output_hidden_states: Optional[bool] = None,
	return_dict: Optional[bool] = None,
	) -> Union[Tuple[torch.Tensor], SequenceClassifierOutputWithPast]:
	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

	transformer_outputs = self.transformer(
	input_ids,
	past_key_values=past_key_values,
	attention_mask=attention_mask,
	head_mask=head_mask,
	inputs_embeds=inputs_embeds,
	use_cache=use_cache,
	output_attentions=output_attentions,
	output_hidden_states=output_hidden_states,
	return_dict=return_dict,
	)

	hidden_states = transformer_outputs[0]
	logits = self.score(hidden_states)

	if input_ids is not None:
	batch_size = input_ids.shape[0]
	else:
	batch_size = inputs_embeds.shape[0]

	if self.config.pad_token_id is None and batch_size != 1:
	raise ValueError("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:
	sequence_lengths = torch.ne(input_ids, self.config.pad_token_id).sum(dim=-1) - 1
	else:
	sequence_lengths = -1
	logger.warning(
	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 = None
	if labels is not None:
	if self.config.problem_type is None:
	if self.num_labels == 1:
	self.config.problem_type = "regression"
	elif self.num_labels > 1 and (labels.dtype == torch.long or labels.dtype == torch.int):
	self.config.problem_type = "single_label_classification"
	else:
	self.config.problem_type = "multi_label_classification"

	if self.config.problem_type == "regression":
	loss_fct = MSELoss()
	if self.num_labels == 1:
	loss = loss_fct(pooled_logits.squeeze(), labels.squeeze())
	else:
	loss = loss_fct(pooled_logits, labels)
	elif self.config.problem_type == "single_label_classification":
	loss_fct = CrossEntropyLoss()
	loss = loss_fct(pooled_logits, labels)
	elif self.config.problem_type == "multi_label_classification":
	loss_fct = BCEWithLogitsLoss()
	loss = loss_fct(pooled_logits, labels)
	if not return_dict:
	output = (pooled_logits,) + transformer_outputs[1:]
	return ((loss,) + output) if loss is not None else output

	return SequenceClassifierOutputWithPast(
	loss=loss,
	logits=pooled_logits,
	past_key_values=transformer_outputs.past_key_values,
	hidden_states=transformer_outputs.hidden_states,
	attentions=transformer_outputs.attentions,
	)


	@add_start_docstrings(
	"""
	Falcon Model with a token classification head on top (a linear layer on top of the hidden-states output) e.g. for
	Named-Entity-Recognition (NER) tasks.
	""",
	FALCON_START_DOCSTRING,
	)
	class FalconForTokenClassification(FalconPreTrainedModel):
	def __init__(self, config: FalconConfig):
	super().__init__(config)
	self.num_labels = config.num_labels

	self.transformer = FalconModel(config)
	if getattr(config, "classifier_dropout", None) is not None:
	classifier_dropout = config.classifier_dropout
	elif getattr(config, "hidden_dropout", None) is not None:
	classifier_dropout = config.hidden_dropout
	else:
	classifier_dropout = 0.1
	self.dropout = nn.Dropout(classifier_dropout)
	self.classifier = nn.Linear(config.hidden_size, config.num_labels)

	# Initialize weights and apply final processing
	self.post_init()

	@add_start_docstrings_to_model_forward(FALCON_INPUTS_DOCSTRING)
	@add_code_sample_docstrings(
	checkpoint=_CHECKPOINT_FOR_DOC,
	output_type=TokenClassifierOutput,
	config_class=_CONFIG_FOR_DOC,
	)
	def forward(
	self,
	input_ids: Optional[torch.LongTensor] = None,
	past_key_values: Optional[Tuple[Tuple[torch.Tensor, torch.Tensor], ...]] = None,
	attention_mask: Optional[torch.Tensor] = None,
	head_mask: Optional[torch.Tensor] = None,
	inputs_embeds: Optional[torch.Tensor] = None,
	labels: Optional[torch.Tensor] = None,
	use_cache: Optional[bool] = None,
	output_attentions: Optional[bool] = None,
	output_hidden_states: Optional[bool] = None,
	return_dict: Optional[bool] = None,
	) -> Union[Tuple[torch.Tensor], TokenClassifierOutput]:
	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

	transformer_outputs = self.transformer(
	input_ids,
	past_key_values=past_key_values,
	attention_mask=attention_mask,
	head_mask=head_mask,
	inputs_embeds=inputs_embeds,
	use_cache=use_cache,
	output_attentions=output_attentions,
	output_hidden_states=output_hidden_states,
	return_dict=return_dict,
	)

	hidden_states = transformer_outputs[0]
	hidden_states = self.dropout(hidden_states)
	logits = self.classifier(hidden_states)

	loss = None
	if labels is not None:
	batch_size, seq_length = labels.shape
	loss_fct = CrossEntropyLoss()
	loss = loss_fct(
	logits.view(batch_size * seq_length, self.num_labels), labels.view(batch_size * seq_length)
	)

	if not return_dict:
	output = (logits,) + transformer_outputs[2:]
	return ((loss,) + output) if loss is not None else output

	return TokenClassifierOutput(
	loss=loss,
	logits=logits,
	hidden_states=transformer_outputs.hidden_states,
	attentions=transformer_outputs.attentions,
	)


	@add_start_docstrings(
	"""
	The Falcon Model transformer with a span classification head on top for extractive question-answering tasks like
	SQuAD (a linear layers on top of the hidden-states output to compute `span start logits` and `span end logits`).
	""",
	FALCON_START_DOCSTRING,
	)
	class FalconForQuestionAnswering(FalconPreTrainedModel):
	def __init__(self, config):
	super().__init__(config)
	self.transformer = FalconModel(config)
	self.qa_outputs = nn.Linear(config.hidden_size, 2)

	# Initialize weights and apply final processing
	self.post_init()

	@add_start_docstrings_to_model_forward(FALCON_INPUTS_DOCSTRING)
	def forward(
	self,
	input_ids: Optional[torch.LongTensor] = None,
	attention_mask: Optional[torch.FloatTensor] = None,
	head_mask: Optional[torch.FloatTensor] = None,
	inputs_embeds: Optional[torch.FloatTensor] = None,
	start_positions: Optional[torch.LongTensor] = None,
	end_positions: Optional[torch.LongTensor] = None,
	output_attentions: Optional[bool] = None,
	output_hidden_states: Optional[bool] = None,
	return_dict: Optional[bool] = None,
	) -> Union[Tuple, QuestionAnsweringModelOutput]:
	r"""
	start_positions (`torch.LongTensor` of shape `(batch_size,)`, optional):
	Labels for position (index) of the start of the labelled span for computing the token classification loss.
	Positions are clamped to the length of the sequence (`sequence_length`). Position outside of the sequence
	are not taken into account for computing the loss.
	end_positions (`torch.LongTensor` of shape `(batch_size,)`, optional):
	Labels for position (index) of the end of the labelled span for computing the token classification loss.
	Positions are clamped to the length of the sequence (`sequence_length`). Position outside of the sequence
	are not taken into account for computing the loss.
	"""
	return_dict = return_dict if return_dict is not None else self.config.use_return_dict

	outputs = self.transformer(
	input_ids,
	attention_mask=attention_mask,
	head_mask=head_mask,
	inputs_embeds=inputs_embeds,
	output_attentions=output_attentions,
	output_hidden_states=output_hidden_states,
	return_dict=return_dict,
	)

	sequence_output = outputs[0]

	logits = self.qa_outputs(sequence_output)
	start_logits, end_logits = logits.split(1, dim=-1)
	start_logits = start_logits.squeeze(-1).contiguous()
	end_logits = end_logits.squeeze(-1).contiguous()

	total_loss = None
	if start_positions is not None and end_positions is not None:
	# If we are on multi-GPU, split add a dimension
	if len(start_positions.size()) > 1:
	start_positions = start_positions.squeeze(-1)
	if len(end_positions.size()) > 1:
	end_positions = end_positions.squeeze(-1)
	# sometimes the start/end positions are outside our model inputs, we ignore these terms
	ignored_index = start_logits.size(1)
	start_positions = start_positions.clamp(0, ignored_index)
	end_positions = end_positions.clamp(0, ignored_index)

	loss_fct = CrossEntropyLoss(ignore_index=ignored_index)
	start_loss = loss_fct(start_logits, start_positions)
	end_loss = loss_fct(end_logits, end_positions)
	total_loss = (start_loss + end_loss) / 2

	if not return_dict:
	output = (start_logits, end_logits) + outputs[2:]
	return ((total_loss,) + output) if total_loss is not None else output

	return QuestionAnsweringModelOutput(
	loss=total_loss,
	start_logits=start_logits,
	end_logits=end_logits,
	hidden_states=outputs.hidden_states,
	attentions=outputs.attentions,
	)