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# Copyright 2023 The Flax Authors.
#
# 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, Any, Optional, Tuple
import jax
import jax.numpy as jnp
import numpy as np
from flax import linen as nn
from flax import struct
from flax.core.frozen_dict import FrozenDict, freeze, unfreeze
from flax.traverse_util import flatten_dict, unflatten_dict
from jax import lax
from transformers.modeling_flax_outputs import FlaxBaseModelOutput, FlaxCausalLMOutput
from transformers.modeling_flax_utils import FlaxPreTrainedModel
from .configuration_transformerlm import TransformerLMConfig
@struct.dataclass
class TransformerConfig:
"""Global hyperparameters used to minimize obnoxious kwarg plumbing."""
vocab_size: int
output_vocab_size: int
share_embeddings: bool = False
logits_via_embedding: bool = False
dtype: Any = jnp.float32
emb_dim: int = 512
num_heads: int = 8
num_layers: int = 6
qkv_dim: int = 512
mlp_dim: int = 2048
max_len: int = 2048
dropout_rate: float = 0.1
attention_dropout_rate: float = 0.1
deterministic: bool = False
decode: bool = False
kernel_init: Callable = nn.initializers.xavier_uniform()
bias_init: Callable = nn.initializers.normal(stddev=1e-6)
posemb_init: Optional[Callable] = None
def shift_right(x, axis=1):
"""Shift the input to the right by padding and slicing on axis."""
pad_widths = [(0, 0)] * len(x.shape)
pad_widths[axis] = (1, 0)
padded = jnp.pad(
x, pad_widths, mode='constant', constant_values=x.dtype.type(0))
return lax.dynamic_slice_in_dim(padded, 0, padded.shape[axis] - 1, axis)
def shift_inputs(x, segment_ids=None, axis=1):
"""Shift inputs and replace EOS by 0 for packed inputs."""
shifted = shift_right(x, axis=axis)
# For packed targets, the first shifted token of a new sequence is made
# 0, rather than being the EOS token for the last sequence.
if segment_ids is not None:
shifted *= (segment_ids==shift_right(segment_ids, axis=axis))
return shifted
def sinusoidal_init(max_len=2048,
min_scale=1.0,
max_scale=10000.0):
"""1D Sinusoidal Position Embedding Initializer.
Args:
max_len: maximum possible length for the input.
min_scale: float: minimum frequency-scale in sine grating.
max_scale: float: maximum frequency-scale in sine grating.
Returns:
output: init function returning `(1, max_len, d_feature)`
"""
def init(key, shape, dtype=np.float32):
"""Sinusoidal init."""
del key, dtype
d_feature = shape[-1]
pe = np.zeros((max_len, d_feature), dtype=np.float32)
position = np.arange(0, max_len)[:, np.newaxis]
scale_factor = -np.log(max_scale / min_scale) / (d_feature // 2 - 1)
div_term = min_scale * np.exp(np.arange(0, d_feature // 2) * scale_factor)
pe[:, :d_feature // 2] = np.sin(position * div_term)
pe[:, d_feature // 2: 2 * (d_feature // 2)] = np.cos(position * div_term)
pe = pe[np.newaxis, :, :] # [1, max_len, d_feature]
return jnp.array(pe)
return init
class AddPositionEmbs(nn.Module):
"""Adds (optionally learned) positional embeddings to the inputs.
Args:
config: TransformerConfig dataclass containing hyperparameters.
decode: whether to run in single-position autoregressive mode.
"""
config: TransformerConfig
decode: bool = False
@nn.compact
def __call__(self,
inputs,
inputs_positions=None):
"""Applies AddPositionEmbs module.
By default this layer uses a fixed sinusoidal embedding table. If a
learned position embedding is desired, pass an initializer to
posemb_init in the configuration.
Args:
inputs: input data.
inputs_positions: input position indices for packed sequences.
Returns:
output: `(bs, timesteps, in_dim)`
"""
config = self.config
# inputs.shape is (batch_size, seq_len, emb_dim)
assert inputs.ndim==3, ('Number of dimensions should be 3,'
' but it is: %d' % inputs.ndim)
length = inputs.shape[1]
pos_emb_shape = (1, config.max_len, inputs.shape[-1])
if config.posemb_init is None:
# Use a fixed (non-learned) sinusoidal position embedding.
pos_embedding = sinusoidal_init(max_len=config.max_len)(None,
pos_emb_shape,
None)
else:
pos_embedding = self.param('pos_embedding', config.posemb_init,
pos_emb_shape)
pe = pos_embedding[:, :length, :]
# We use a cache position index for tracking decoding position.
if self.decode:
is_initialized = self.has_variable('cache', 'cache_index')
cache_index = self.variable('cache', 'cache_index',
lambda: jnp.array(0, dtype=jnp.uint32))
if is_initialized:
i = cache_index.value
cache_index.value = i + 1
_, _, df = pos_embedding.shape
pe = lax.dynamic_slice(pos_embedding,
jnp.array((0, i, 0)),
(1, 1, df))
if inputs_positions is None:
# normal unpacked case:
return inputs + pe
else:
# for packed data we need to use known position indices:
return inputs + jnp.take(pe[0], inputs_positions, axis=0)
class MlpBlock(nn.Module):
"""Transformer MLP / feed-forward block.
Args:
config: TransformerConfig dataclass containing hyperparameters.
out_dim: optionally specify out dimension.
"""
config: TransformerConfig
out_dim: Optional[int] = None
@nn.compact
def __call__(self, inputs):
"""Applies Transformer MlpBlock module."""
config = self.config
actual_out_dim = (inputs.shape[-1] if self.out_dim is None
else self.out_dim)
x = nn.Dense(
config.mlp_dim,
dtype=config.dtype,
kernel_init=config.kernel_init,
bias_init=config.bias_init)(
inputs)
x = nn.relu(x)
x = nn.Dropout(rate=config.dropout_rate)(
x, deterministic=config.deterministic)
output = nn.Dense(
actual_out_dim,
dtype=config.dtype,
kernel_init=config.kernel_init,
bias_init=config.bias_init)(
x)
output = nn.Dropout(rate=config.dropout_rate)(
output, deterministic=config.deterministic)
return output
class EncoderDecoder1DBlock(nn.Module):
"""Transformer encoder-decoder layer.
Args:
config: TransformerConfig dataclass containing hyperparameters.
"""
config: TransformerConfig
@nn.compact
def __call__(self,
inputs,
decoder_mask=None,
encoder_decoder_mask=None):
"""Applies EncoderDecoder1DBlock module.
Args:
inputs: input data for decoder
decoder_mask: decoder self-attention mask.
encoder_decoder_mask: encoder-decoder attention mask.
Returns:
output after transformer encoder-decoder block.
"""
config = self.config
# Decoder block.
assert inputs.ndim==3
x = nn.LayerNorm(dtype=config.dtype)(inputs)
x = nn.SelfAttention(
num_heads=config.num_heads,
dtype=config.dtype,
qkv_features=config.qkv_dim,
kernel_init=config.kernel_init,
bias_init=config.bias_init,
use_bias=False,
broadcast_dropout=False,
dropout_rate=config.attention_dropout_rate,
deterministic=config.deterministic,
decode=config.decode)(x, decoder_mask)
x = nn.Dropout(rate=config.dropout_rate)(
x, deterministic=config.deterministic)
x = x + inputs
# MLP block.
z = nn.LayerNorm(dtype=config.dtype)(x)
z = MlpBlock(config=config)(z)
return x + z
# Copyright 2021 The Eleuther AI and 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.
class FlaxTransformerLMPreTrainedModel(FlaxPreTrainedModel):
config_class = TransformerLMConfig
base_model_prefix = "decoder"
module_class: nn.Module = None
def __init__(
self,
config: TransformerLMConfig,
input_shape: Tuple = (1, 1),
seed: int = 0,
dtype: jnp.dtype = jnp.float32,
_do_init: bool = True,
**kwargs,
):
module = self.module_class(config=config, dtype=dtype, **kwargs)
def token_id_to_logits(state, token_id):
logits, cache = state
output = self.module.apply(
{
"params": self.params,
"cache": cache
},
token_id,
None,
None,
True,
False,
False,
False,
True,
rngs={},
mutable=["cache"],
)
lm_output, new_vars = output
logits = lm_output.logits
cache = unfreeze(new_vars["cache"])
return (logits, cache), logits
self.scan_body_fn = token_id_to_logits
super().__init__(config, module, input_shape=input_shape, seed=seed, dtype=dtype, _do_init=_do_init)
def init_weights(self, rng: jax.random.PRNGKey, input_shape: Tuple, params: FrozenDict = None) -> FrozenDict:
# init input tensors
input_ids = jnp.zeros(input_shape, dtype="i4")
attention_mask = jnp.ones_like(input_ids)
position_ids = jnp.broadcast_to(jnp.arange(jnp.atleast_2d(input_ids).shape[-1]), input_shape)
params_rng, dropout_rng = jax.random.split(rng)
rngs = {"params": params_rng, "dropout": dropout_rng}
random_params = self.module.init(rngs, input_ids, attention_mask, position_ids, return_dict=False)["params"]
if params is not None:
random_params = flatten_dict(unfreeze(random_params))
params = flatten_dict(unfreeze(params))
for missing_key in self._missing_keys:
params[missing_key] = random_params[missing_key]
self._missing_keys = set()
return freeze(unflatten_dict(params))
else:
return random_params
def init_cache(self, batch_size, max_length):
r"""
Args:
batch_size (`int`):
batch_size used for fast auto-regressive decoding. Defines the batch size of the initialized cache.
max_length (`int`):
maximum possible length for auto-regressive decoding. Defines the sequence length of the initialized
cache.
"""
# init input variables to retrieve cache
input_ids = jnp.ones((batch_size, max_length))
attention_mask = jnp.ones_like(input_ids)
position_ids = jnp.broadcast_to(jnp.arange(jnp.atleast_2d(input_ids).shape[-1]), input_ids.shape)
init_variables = self.module.init(
jax.random.PRNGKey(0), input_ids, attention_mask, position_ids, return_dict=False, init_cache=True
)
return unfreeze(init_variables["cache"])
def __call__(
self,
input_ids,
attention_mask=None,
position_ids=None,
params: dict = None,
past_key_values: dict = None,
dropout_rng: jax.random.PRNGKey = None,
train: bool = False,
output_attentions: Optional[bool] = None,
output_hidden_states: Optional[bool] = None,
return_dict: Optional[bool] = None,
):
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
)
return_dict = return_dict if return_dict is not None else self.config.return_dict
batch_size, sequence_length = input_ids.shape
if position_ids is None:
if past_key_values is not None:
raise ValueError("Make sure to provide `position_ids` when passing `past_key_values`.")
position_ids = jnp.broadcast_to(jnp.arange(sequence_length)[None, :], (batch_size, sequence_length))
if attention_mask is None:
attention_mask = jnp.ones((batch_size, sequence_length))
# Handle any PRNG if needed
rngs = {}
if dropout_rng is not None:
rngs["dropout"] = dropout_rng
inputs = {"params": params or self.params}
# if past_key_values are passed then cache is already initialized a private flag init_cache has to be passed down to ensure cache is used. It has to be made sure that cache is marked as mutable so that it can be changed by FlaxGPTNeoAttention module
if past_key_values:
inputs["cache"] = past_key_values
mutable = ["cache"]
else:
mutable = False
if input_ids.shape[1] > 1:
input_ids = jnp.insert(input_ids, 0, 0, axis=1) # Insert 0 at the beginning of prompt
if self.module.use_cache:
# Progressive cache loop
seq_length = input_ids.shape[1]
vcab_size = self.module.config.vocab_size
logits = jnp.zeros((1, 1, vcab_size), dtype=self.dtype)
cache = inputs["cache"]
initial_state = (logits, cache)
input_tokens = jnp.reshape(input_ids, (seq_length, 1, 1))
last, all_logits = lax.scan(self.scan_body_fn, initial_state, input_tokens)
last_logits, last_cache = last
lm_logits = jnp.reshape(all_logits, (1, seq_length, vcab_size))
if input_ids.shape[1] > 1:
lm_logits = lm_logits[:, 1:, :] # Ignore leading zeros in prompts
if not return_dict:
outputs = (lm_logits,) + (last_cache,)
else:
outputs = (FlaxCausalLMOutput(logits=lm_logits, hidden_states=None, attentions=None), {"cache": last_cache})
else:
output = self.module.apply(
inputs,
jnp.array(input_ids, dtype="i4"),
jnp.array(attention_mask, dtype="i4"),
jnp.array(position_ids, dtype="i4"),
not train,
False,
output_attentions,
output_hidden_states,
return_dict,
rngs=rngs,
mutable=mutable,
)
lm_logits = output.logits
if input_ids.shape[1] > 1:
lm_logits = lm_logits[:, 1:, :] # Ignore leading zeros in prompts
if not return_dict:
outputs = (lm_logits,) + output[1:]
else:
outputs = FlaxCausalLMOutput(logits=lm_logits, hidden_states=output.hidden_states, attentions=output.attentions)
# add updated cache to model output
if past_key_values is not None and return_dict:
outputs, past_key_values = outputs
outputs["past_key_values"] = unfreeze(past_key_values["cache"])
return outputs
elif past_key_values is not None and not return_dict:
outputs, past_key_values = outputs
outputs = outputs[:1] + (unfreeze(past_key_values["cache"]),) + outputs[1:]
return outputs
class FlaxTransformerLMModule(nn.Module):
config: TransformerConfig
def setup(self):
config = self.config
self.output_embed = nn.Embed(
num_embeddings=config.output_vocab_size,
features=config.emb_dim,
embedding_init=nn.initializers.normal(stddev=1.0),
name='Embed_0'
)
self.pos_embed = AddPositionEmbs(config=config, decode=config.decode, name='posembed_output')
self.dropout = nn.Dropout(rate=config.dropout_rate)
self.h_layers = [EncoderDecoder1DBlock(config=config, name=f'encoderdecoderblock_{i}')
for i in range(config.num_layers)]
self.ln_f = nn.LayerNorm(dtype=config.dtype, name='encoderdecoder_norm')
def __call__(
self,
input_ids,
attention_mask,
position_ids,
deterministic=True,
init_cache: bool = False,
output_attentions: bool = False,
output_hidden_states: bool = False,
return_dict: bool = True,
):
config = self.config
y = input_ids.astype('int32')
y = self.output_embed(y)
y = self.pos_embed(y, inputs_positions=position_ids)
y = self.dropout(y, deterministic=config.deterministic)
y = y.astype(config.dtype)
for h in self.h_layers:
y = h(y, decoder_mask=attention_mask, encoder_decoder_mask=None)
outputs = (y, None, None)
hidden_states = outputs[0]
hidden_states = self.ln_f(hidden_states)
if output_hidden_states:
all_hidden_states = outputs[1] + (hidden_states,)
outputs = (hidden_states, all_hidden_states) + outputs[2:]
else:
outputs = (hidden_states,) + outputs[1:]
if not return_dict:
return tuple(v for v in outputs if v is not None)
return FlaxBaseModelOutput(
last_hidden_state=hidden_states,
hidden_states=outputs[1],
attentions=outputs[-1],
)
class FlaxTransformerLMModel(FlaxTransformerLMPreTrainedModel):
module_class = FlaxTransformerLMModule
class FlaxTransformerLMForCausalLMModule(nn.Module):
config: TransformerLMConfig
dtype: jnp.dtype = jnp.float32
kernel_init: Callable = nn.initializers.xavier_uniform()
bias_init: Callable = nn.initializers.normal(stddev=1e-6)
posemb_init: Callable = None
use_cache = False
def convert_config(self, cfg: TransformerLMConfig):
return TransformerConfig(
vocab_size=cfg.vocab_size,
output_vocab_size=cfg.vocab_size,
logits_via_embedding=cfg.logits_via_embedding,
dtype=self.dtype,
emb_dim=cfg.emb_dim,
num_heads=cfg.num_heads,
num_layers=cfg.num_layers,
qkv_dim=cfg.qkv_dim,
mlp_dim=cfg.mlp_dim,
max_len=cfg.max_len,
dropout_rate=cfg.dropout_rate,
attention_dropout_rate=cfg.attention_dropout_rate,
deterministic=cfg.deterministic,
decode=cfg.decode and self.use_cache,
kernel_init=self.kernel_init,
bias_init=self.bias_init,
posemb_init=self.posemb_init,
)
def setup(self):
config_ext = self.convert_config(self.config)
self.transformer = FlaxTransformerLMModule(config_ext, name='decoder')
self.lm_head = nn.Dense(
self.config.output_vocab_size,
dtype=self.dtype,
kernel_init=self.kernel_init,
bias_init=self.bias_init,
name='logitdense',
)
def __call__(
self,
input_ids,
attention_mask,
position_ids,
deterministic: bool = True,
init_cache: bool = False,
output_attentions: bool = False,
output_hidden_states: bool = False,
return_dict: bool = True,
):
decoder_mask = None
inputs_positions = None
outputs = self.transformer(
input_ids,
decoder_mask,
inputs_positions,
deterministic=deterministic,
init_cache=init_cache,
output_attentions=output_attentions,
output_hidden_states=output_hidden_states,
return_dict=return_dict,
)
hidden_states = outputs[0]
lm_logits = self.lm_head(hidden_states)
if not return_dict:
return (lm_logits,) + outputs[1:]
return FlaxCausalLMOutput(logits=lm_logits, hidden_states=outputs.hidden_states, attentions=outputs.attentions)
class FlaxTransformerLMForCausalLM(FlaxTransformerLMPreTrainedModel):
module_class = FlaxTransformerLMForCausalLMModule
def prepare_inputs_for_generation(self, input_ids, max_length, attention_mask: Optional[jax.Array] = None):
self.module_class.use_cache = True
# initializing the cache
batch_size, seq_length = input_ids.shape
past_key_values = self.init_cache(batch_size, max_length)
# Note that usually one would have to put 0's in the attention_mask for x > input_ids.shape[-1] and x < cache_length.
# But since GPTNeo uses a causal mask, those positions are masked anyways.
# Thus we can create a single static attention_mask here, which is more efficient for compilation
extended_attention_mask = jnp.ones((batch_size, max_length), dtype="i4")
if attention_mask is not None:
position_ids = attention_mask.cumsum(axis=-1) - 1
extended_attention_mask = lax.dynamic_update_slice(extended_attention_mask, attention_mask, (0, 0))
else:
position_ids = jnp.broadcast_to(jnp.arange(seq_length, dtype="i4")[None, :], (batch_size, seq_length))
return {
"past_key_values": past_key_values,
"attention_mask": extended_attention_mask,
"position_ids": position_ids,
}
def update_inputs_for_generation(self, model_outputs, model_kwargs):
model_kwargs["past_key_values"] = model_outputs.past_key_values
model_kwargs["position_ids"] = model_kwargs["position_ids"][:, -1:] + 1
return model_kwargs
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