# coding=utf-8
# Copyright 2018 The Google Flax Team Authors and The HuggingFace Inc. team.
#
# 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.
from typing import Callable, Dict
import numpy as np
import flax.linen as nn
import jax
import jax.numpy as jnp
from ...file_utils import add_start_docstrings, add_start_docstrings_to_model_forward
from ...modeling_flax_utils import FlaxPreTrainedModel, gelu
from ...utils import logging
from .configuration_roberta import RobertaConfig
logger = logging.get_logger(__name__)
_CONFIG_FOR_DOC = "RobertaConfig"
_TOKENIZER_FOR_DOC = "RobertaTokenizer"
ROBERTA_START_DOCSTRING = r"""
This model inherits from :class:`~transformers.FlaxPreTrainedModel`. Check the superclass documentation for the
generic methods the library implements for all its model (such as downloading, saving and converting weights from
PyTorch models)
This model is also a Flax Linen `flax.nn.Module
<https://flax.readthedocs.io/en/latest/_autosummary/flax.nn.module.html>`__ subclass. Use it as a regular Flax
Module and refer to the Flax documentation for all matter related to general usage and behavior.
Finally, this model supports inherent JAX features such as:
- `Just-In-Time (JIT) compilation <https://jax.readthedocs.io/en/latest/jax.html#just-in-time-compilation-jit>`__
- `Automatic Differentiation <https://jax.readthedocs.io/en/latest/jax.html#automatic-differentiation>`__
- `Vectorization <https://jax.readthedocs.io/en/latest/jax.html#vectorization-vmap>`__
- `Parallelization <https://jax.readthedocs.io/en/latest/jax.html#parallelization-pmap>`__
Parameters:
config (:class:`~transformers.RobertaConfig`): 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 :meth:`~transformers.PreTrainedModel.from_pretrained` method to load the model
weights.
"""
ROBERTA_INPUTS_DOCSTRING = r"""
Args:
input_ids (:obj:`numpy.ndarray` of shape :obj:`({0})`):
Indices of input sequence tokens in the vocabulary.
Indices can be obtained using :class:`~transformers.BertTokenizer`. See
:func:`transformers.PreTrainedTokenizer.encode` and :func:`transformers.PreTrainedTokenizer.__call__` for
details.
`What are input IDs? <../glossary.html#input-ids>`__
attention_mask (:obj:`numpy.ndarray` of shape :obj:`({0})`, `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.html#attention-mask>`__
token_type_ids (:obj:`numpy.ndarray` of shape :obj:`({0})`, `optional`):
Segment token indices to indicate first and second portions of the inputs. Indices are selected in ``[0,
1]``:
- 0 corresponds to a `sentence A` token,
- 1 corresponds to a `sentence B` token.
`What are token type IDs? <../glossary.html#token-type-ids>`__
position_ids (:obj:`numpy.ndarray` of shape :obj:`({0})`, `optional`):
Indices of positions of each input sequence tokens in the position embeddings. Selected in the range ``[0,
config.max_position_embeddings - 1]``.
return_dict (:obj:`bool`, `optional`):
Whether or not to return a :class:`~transformers.file_utils.ModelOutput` instead of a plain tuple.
"""
# Copied from transformers.models.bert.modeling_flax_bert.FlaxBertLayerNorm with Bert->Roberta
class FlaxRobertaLayerNorm(nn.Module):
"""
Layer normalization (https://arxiv.org/abs/1607.06450). Operates on the last axis of the input data.
"""
epsilon: float = 1e-6
dtype: jnp.dtype = jnp.float32 # the dtype of the computation
bias: bool = True # If True, bias (beta) is added.
scale: bool = True # If True, multiply by scale (gamma). When the next layer is linear
# (also e.g. nn.relu), this can be disabled since the scaling will be
# done by the next layer.
bias_init: jnp.ndarray = nn.initializers.zeros
scale_init: jnp.ndarray = nn.initializers.ones
@nn.compact
def __call__(self, x):
"""
Applies layer normalization on the input. It normalizes the activations of the layer for each given example in
a batch independently, rather than across a batch like Batch Normalization. i.e. applies a transformation that
maintains the mean activation within each example close to 0 and the activation standard deviation close to 1
Args:
x: the inputs
Returns:
Normalized inputs (the same shape as inputs).
"""
features = x.shape[-1]
mean = jnp.mean(x, axis=-1, keepdims=True)
mean2 = jnp.mean(jax.lax.square(x), axis=-1, keepdims=True)
var = mean2 - jax.lax.square(mean)
mul = jax.lax.rsqrt(var + self.epsilon)
if self.scale:
mul = mul * jnp.asarray(self.param("gamma", self.scale_init, (features,)), self.dtype)
y = (x - mean) * mul
if self.bias:
y = y + jnp.asarray(self.param("beta", self.bias_init, (features,)), self.dtype)
return y
# Copied from transformers.models.bert.modeling_flax_bert.FlaxBertEmbedding with Bert->Roberta
class FlaxRobertaEmbedding(nn.Module):
"""
Specify a new class for doing the embedding stuff as Flax's one use 'embedding' for the parameter name and PyTorch
use 'weight'
"""
vocab_size: int
hidden_size: int
emb_init: Callable[..., np.ndarray] = nn.initializers.normal(stddev=0.1)
@nn.compact
def __call__(self, inputs):
embedding = self.param("weight", self.emb_init, (self.vocab_size, self.hidden_size))
return jnp.take(embedding, inputs, axis=0)
# Copied from transformers.models.bert.modeling_flax_bert.FlaxBertEmbeddings with Bert->Roberta
class FlaxRobertaEmbeddings(nn.Module):
"""Construct the embeddings from word, position and token_type embeddings."""
vocab_size: int
hidden_size: int
type_vocab_size: int
max_length: int
@nn.compact
def __call__(self, input_ids, token_type_ids, position_ids, attention_mask):
# Embed
w_emb = FlaxRobertaEmbedding(self.vocab_size, self.hidden_size, name="word_embeddings")(
jnp.atleast_2d(input_ids.astype("i4"))
)
p_emb = FlaxRobertaEmbedding(self.max_length, self.hidden_size, name="position_embeddings")(
jnp.atleast_2d(position_ids.astype("i4"))
)
t_emb = FlaxRobertaEmbedding(self.type_vocab_size, self.hidden_size, name="token_type_embeddings")(
jnp.atleast_2d(token_type_ids.astype("i4"))
)
# Sum all embeddings
summed_emb = w_emb + jnp.broadcast_to(p_emb, w_emb.shape) + t_emb
# Layer Norm
layer_norm = FlaxRobertaLayerNorm(name="layer_norm")(summed_emb)
return layer_norm
# Copied from transformers.models.bert.modeling_flax_bert.FlaxBertAttention with Bert->Roberta
class FlaxRobertaAttention(nn.Module):
num_heads: int
head_size: int
@nn.compact
def __call__(self, hidden_state, attention_mask):
# Attention mask comes in as attention_mask.shape == (*batch_sizes, kv_length)
# FLAX expects: attention_mask.shape == (*batch_sizes, 1, 1, kv_length) such that it is broadcastable
# with attn_weights.shape == (*batch_sizes, num_heads, q_length, kv_length)
attention_mask = jnp.expand_dims(attention_mask, axis=(-3, -2))
self_att = nn.attention.SelfAttention(num_heads=self.num_heads, qkv_features=self.head_size, name="self")(
hidden_state, attention_mask
)
layer_norm = FlaxRobertaLayerNorm(name="layer_norm")(self_att + hidden_state)
return layer_norm
# Copied from transformers.models.bert.modeling_flax_bert.FlaxBertIntermediate with Bert->Roberta
class FlaxRobertaIntermediate(nn.Module):
output_size: int
@nn.compact
def __call__(self, hidden_state):
# TODO: Add ACT2FN reference to change activation function
dense = nn.Dense(features=self.output_size, name="dense")(hidden_state)
return gelu(dense)
# Copied from transformers.models.bert.modeling_flax_bert.FlaxBertOutput with Bert->Roberta
class FlaxRobertaOutput(nn.Module):
@nn.compact
def __call__(self, intermediate_output, attention_output):
hidden_state = nn.Dense(attention_output.shape[-1], name="dense")(intermediate_output)
hidden_state = FlaxRobertaLayerNorm(name="layer_norm")(hidden_state + attention_output)
return hidden_state
class FlaxRobertaLayer(nn.Module):
num_heads: int
head_size: int
intermediate_size: int
@nn.compact
def __call__(self, hidden_state, attention_mask):
attention = FlaxRobertaAttention(self.num_heads, self.head_size, name="attention")(
hidden_state, attention_mask
)
intermediate = FlaxRobertaIntermediate(self.intermediate_size, name="intermediate")(attention)
output = FlaxRobertaOutput(name="output")(intermediate, attention)
return output
# Copied from transformers.models.bert.modeling_flax_bert.FlaxBertLayerCollection with Bert->Roberta
class FlaxRobertaLayerCollection(nn.Module):
"""
Stores N RobertaLayer(s)
"""
num_layers: int
num_heads: int
head_size: int
intermediate_size: int
@nn.compact
def __call__(self, inputs, attention_mask):
assert self.num_layers > 0, f"num_layers should be >= 1, got ({self.num_layers})"
# Initialize input / output
input_i = inputs
# Forward over all encoders
for i in range(self.num_layers):
layer = FlaxRobertaLayer(self.num_heads, self.head_size, self.intermediate_size, name=f"{i}")
input_i = layer(input_i, attention_mask)
return input_i
# Copied from transformers.models.bert.modeling_flax_bert.FlaxBertEncoder with Bert->Roberta
class FlaxRobertaEncoder(nn.Module):
num_layers: int
num_heads: int
head_size: int
intermediate_size: int
@nn.compact
def __call__(self, hidden_state, attention_mask):
layer = FlaxRobertaLayerCollection(
self.num_layers, self.num_heads, self.head_size, self.intermediate_size, name="layer"
)(hidden_state, attention_mask)
return layer
# Copied from transformers.models.bert.modeling_flax_bert.FlaxBertPooler with Bert->Roberta
class FlaxRobertaPooler(nn.Module):
@nn.compact
def __call__(self, hidden_state):
cls_token = hidden_state[:, 0]
out = nn.Dense(hidden_state.shape[-1], name="dense")(cls_token)
return jax.lax.tanh(out)
# Copied from transformers.models.bert.modeling_flax_bert.FlaxBertModule with Bert->Roberta
class FlaxRobertaModule(nn.Module):
vocab_size: int
hidden_size: int
type_vocab_size: int
max_length: int
num_encoder_layers: int
num_heads: int
head_size: int
intermediate_size: int
@nn.compact
def __call__(self, input_ids, attention_mask, token_type_ids, position_ids):
# Embedding
embeddings = FlaxRobertaEmbeddings(
self.vocab_size, self.hidden_size, self.type_vocab_size, self.max_length, name="embeddings"
)(input_ids, token_type_ids, position_ids, attention_mask)
# N stacked encoding layers
encoder = FlaxRobertaEncoder(
self.num_encoder_layers, self.num_heads, self.head_size, self.intermediate_size, name="encoder"
)(embeddings, attention_mask)
pooled = FlaxRobertaPooler(name="pooler")(encoder)
return encoder, pooled
[docs]@add_start_docstrings(
"The bare RoBERTa Model transformer outputting raw hidden-states without any specific head on top.",
ROBERTA_START_DOCSTRING,
)
class FlaxRobertaModel(FlaxPreTrainedModel):
"""
The model can behave as an encoder (with only self-attention) as well as a decoder, in which case a layer of
cross-attention is added between the self-attention layers, following the architecture described in `Attention is
all you need`_ by Ashish Vaswani, Noam Shazeer, Niki Parmar, Jakob Uszkoreit, Llion Jones, Aidan N. Gomez, Lukasz
Kaiser and Illia Polosukhin.
"""
model_class = FlaxRobertaModule
config_class = RobertaConfig
base_model_prefix = "roberta"
@staticmethod
def convert_from_pytorch(pt_state: Dict, config: RobertaConfig) -> Dict:
jax_state = dict(pt_state)
# Need to change some parameters name to match Flax names so that we don't have to fork any layer
for key, tensor in pt_state.items():
# Key parts
key_parts = set(key.split("."))
# Every dense layer has "kernel" parameters instead of "weight"
if "dense.weight" in key:
del jax_state[key]
key = key.replace("weight", "kernel")
jax_state[key] = tensor
# SelfAttention needs also to replace "weight" by "kernel"
if {"query", "key", "value"} & key_parts:
# Flax SelfAttention decomposes the heads (num_head, size // num_heads)
if "bias" in key:
jax_state[key] = tensor.reshape((config.num_attention_heads, -1))
elif "weight":
del jax_state[key]
key = key.replace("weight", "kernel")
tensor = tensor.reshape((config.num_attention_heads, -1, config.hidden_size)).transpose((2, 0, 1))
jax_state[key] = tensor
# SelfAttention output is not a separate layer, remove one nesting
if "attention.output.dense" in key:
del jax_state[key]
key = key.replace("attention.output.dense", "attention.self.out")
jax_state[key] = tensor
# SelfAttention output is not a separate layer, remove nesting on layer norm
if "attention.output.LayerNorm" in key:
del jax_state[key]
key = key.replace("attention.output.LayerNorm", "attention.LayerNorm")
jax_state[key] = tensor
# There are some transposed parameters w.r.t their PyTorch counterpart
if "intermediate.dense.kernel" in key or "output.dense.kernel" in key:
jax_state[key] = tensor.T
# Self Attention output projection needs to be transposed
if "out.kernel" in key:
jax_state[key] = tensor.reshape((config.hidden_size, config.num_attention_heads, -1)).transpose(
1, 2, 0
)
# Pooler needs to transpose its kernel
if "pooler.dense.kernel" in key:
jax_state[key] = tensor.T
# Handle LayerNorm conversion
if "LayerNorm" in key:
del jax_state[key]
# Replace LayerNorm by layer_norm
new_key = key.replace("LayerNorm", "layer_norm")
if "weight" in key:
new_key = new_key.replace("weight", "gamma")
elif "bias" in key:
new_key = new_key.replace("bias", "beta")
jax_state[new_key] = tensor
return jax_state
def __init__(self, config: RobertaConfig, state: dict, seed: int = 0, **kwargs):
model = FlaxRobertaModule(
vocab_size=config.vocab_size,
hidden_size=config.hidden_size,
type_vocab_size=config.type_vocab_size,
max_length=config.max_position_embeddings,
num_encoder_layers=config.num_hidden_layers,
num_heads=config.num_attention_heads,
head_size=config.hidden_size,
intermediate_size=config.intermediate_size,
)
super().__init__(config, model, state, seed)
@property
def module(self) -> nn.Module:
return self._module
[docs] @add_start_docstrings_to_model_forward(ROBERTA_INPUTS_DOCSTRING.format("batch_size, sequence_length"))
def __call__(self, input_ids, token_type_ids=None, attention_mask=None, position_ids=None):
if token_type_ids is None:
token_type_ids = jnp.ones_like(input_ids)
if position_ids is None:
position_ids = jnp.arange(
self.config.pad_token_id + 1, jnp.atleast_2d(input_ids).shape[-1] + self.config.pad_token_id + 1
)
if attention_mask is None:
attention_mask = jnp.ones_like(input_ids)
return self.model.apply(
{"params": self.params},
jnp.array(input_ids, dtype="i4"),
jnp.array(attention_mask, dtype="i4"),
jnp.array(token_type_ids, dtype="i4"),
jnp.array(position_ids, dtype="i4"),
)