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from typing import Optional, Tuple
import jax
from flax import linen as nn
from flax.core import FrozenDict, unfreeze, freeze
from flax.traverse_util import flatten_dict, unflatten_dict
from jax import numpy as jnp
from transformers import FlaxPreTrainedModel
from transformers.modeling_flax_outputs import FlaxBaseModelOutput, FlaxCausalLMOutput
from transformers.modeling_flax_utils import ACT2FN
from .configuration_retnet import RetNetConfig
def rotate_every_two(tensor):
rotate_half_tensor = jnp.stack(
(-tensor[:, :, :, 1::2], tensor[:, :, :, ::2]), axis=-1
)
rotate_half_tensor = rotate_half_tensor.reshape(
rotate_half_tensor.shape[:-2] + (-1,)
)
return rotate_half_tensor
def theta_shift(x, sin, cos):
return (x * cos) + (rotate_every_two(x) * sin)
class FlaxRetNetRelPos(nn.Module):
config: RetNetConfig
dtype: jnp.dtype = jnp.float32
def setup(self) -> None:
angle = 1.0 / (
10000
** jnp.linspace(
0, 1, self.config.hidden_size // self.config.num_rettention_heads // 2
)
)
self.angle = angle.repeat(2).flatten()
self.decay = jnp.log(
1
- 2
** (-5 - jnp.arange(self.config.num_rettention_heads, dtype=jnp.float32))
)
self.recurrent_chunk_size = self.config.recurrent_chunk_size
def __call__(
self,
slen: int,
activate_recurrent: bool = False,
chunkwise_recurrent: bool = False,
):
if activate_recurrent:
sin = jnp.sin(self.angle * (slen - 1))
cos = jnp.cos(self.angle * (slen - 1))
retention_rel_pos = ((sin, cos), jnp.exp(self.decay))
elif chunkwise_recurrent:
index = jnp.arange(slen)
sin = jnp.sin(index[:, None] * self.angle[None, :])
cos = jnp.cos(index[:, None] * self.angle[None, :])
block_index = jnp.arange(self.recurrent_chunk_size)
mask = jnp.tril(
jnp.ones((self.recurrent_chunk_size, self.recurrent_chunk_size))
)
mask = jnp.where(
~mask.astype(jnp.bool_),
float("inf"),
block_index[:, None] - block_index[None, :],
)
mask = jnp.exp(mask * self.decay[:, None, None])
mask = jnp.nan_to_num(mask)
scale = jnp.sqrt(mask.sum(axis=-1, keepdims=True))
mask = mask / scale
cross_decay = jnp.exp(self.decay * self.recurrent_chunk_size)
inner_decay = jnp.exp(self.decay[:, None] * (block_index + 1))
cross_decay = cross_decay[:, None, None]
inner_decay = inner_decay[:, :, None] / (scale / scale[:, -1, None])
retention_rel_pos = ((sin, cos), (mask, cross_decay, inner_decay))
else:
index = jnp.arange(slen)
sin = jnp.sin(index[:, None] * self.angle[None, :])
cos = jnp.cos(index[:, None] * self.angle[None, :])
mask = jnp.tril(jnp.ones((slen, slen)))
mask = jnp.where(
~mask.astype(jnp.bool_), float("inf"), index[:, None] - index[None, :]
)
mask = jnp.exp(mask * self.decay[:, None, None])
mask = jnp.nan_to_num(mask)
mask = mask / jnp.sqrt(mask.sum(axis=-1, keepdims=True))
retention_rel_pos = ((sin, cos), mask)
return retention_rel_pos
class FlaxRetNetFeedForward(nn.Module):
config: RetNetConfig
dtype: jnp.dtype = jnp.float32
def setup(self) -> None:
self.fc1 = nn.Dense(
self.config.intermediate_size,
kernel_init=nn.initializers.xavier_normal(),
dtype=self.dtype,
)
self.fc2 = nn.Dense(
self.config.hidden_size,
kernel_init=nn.initializers.xavier_normal(),
dtype=self.dtype,
)
self.activation_fn = ACT2FN[self.config.hidden_act]
self.activation_dropout = nn.Dropout(rate=self.config.dropout)
self.dropout = nn.Dropout(rate=self.config.dropout)
def __call__(
self,
hidden_states: jnp.ndarray,
deterministic: bool = True,
) -> jnp.ndarray:
hidden_states = self.fc1(hidden_states)
hidden_states = self.activation_fn(hidden_states)
hidden_states = self.activation_dropout(
hidden_states, deterministic=deterministic
)
hidden_states = self.fc2(hidden_states)
hidden_states = self.dropout(hidden_states, deterministic=deterministic)
return hidden_states
class FlaxRetNetRetention(nn.Module):
config: RetNetConfig
dtype: jnp.dtype = jnp.float32
def setup(self) -> None:
self.factor = 2
self.embed_dim = self.config.hidden_size
self.num_heads = self.config.num_rettention_heads
self.head_dim = self.embed_dim * self.factor // self.num_heads
self.key_dim = self.embed_dim // self.num_heads
self.scaling = self.key_dim**-0.5
self.q_proj = nn.Dense(
self.embed_dim,
use_bias=True,
kernel_init=jax.nn.initializers.xavier_normal(),
dtype=self.dtype,
)
self.k_proj = nn.Dense(
self.embed_dim,
use_bias=True,
kernel_init=jax.nn.initializers.xavier_normal(),
dtype=self.dtype,
)
self.v_proj = nn.Dense(
self.embed_dim * self.factor,
use_bias=True,
kernel_init=jax.nn.initializers.xavier_normal(),
dtype=self.dtype,
)
self.g_proj = nn.Dense(
self.embed_dim * self.factor,
use_bias=True,
kernel_init=nn.initializers.xavier_normal(),
dtype=self.dtype,
)
self.out_proj = nn.Dense(
self.embed_dim,
use_bias=True,
kernel_init=jax.nn.initializers.xavier_normal(),
dtype=self.dtype,
)
self.group_norm = nn.LayerNorm(epsilon=1e-6, dtype=self.dtype)
def parallel_forward(self, qr, kr, v, mask):
bsz, tgt_len, embed_dim = v.shape
vr = v.reshape(bsz, tgt_len, self.num_heads, self.head_dim).transpose(
(0, 2, 1, 3)
)
qk_mat = qr @ kr.transpose((0, 1, 3, 2))
qk_mat = qk_mat * mask
qk_mat /= jnp.abs(
jax.lax.stop_gradient(qk_mat).sum(axis=-1, keepdims=True)
).clip(min=1)
output = jnp.matmul(qk_mat, vr)
output = output.transpose((0, 2, 1, 3))
return output
def chunk_recurrent_forward(self, qr, kr, v, inner_mask):
mask, cross_decay, inner_decay = inner_mask
bsz, tgt_len, embed_dim = v.shape
chunk_len = mask.shape[1]
num_chunks = tgt_len // chunk_len
assert tgt_len % chunk_len == 0
qr = qr.reshape(
bsz, self.num_heads, num_chunks, chunk_len, self.key_dim
).transpose((0, 2, 1, 3, 4))
kr = kr.reshape(
bsz, self.num_heads, num_chunks, chunk_len, self.key_dim
).transpose((0, 2, 1, 3, 4))
v = v.reshape(
bsz, num_chunks, chunk_len, self.num_heads, self.head_dim
).transpose((0, 1, 3, 2, 4))
kr_t = kr.transpose((0, 1, 2, 4, 3))
qk_mat = qr @ kr_t
qk_mat = qk_mat
inner_scale = jnp.abs(
jax.lax.stop_gradient(qk_mat).sum(axis=-1, keepdims=True)
).clip(min=1)
qk_mat = qk_mat / inner_scale
inner_output = jnp.matmul(qk_mat, v)
kv = kr_t @ v
kv = kv.reshape(bsz, num_chunks, self.num_heads, self.key_dim, self.head_dim)
kv_recurrent = []
cross_scale = []
kv_state = jnp.zeros((bsz, self.num_heads, self.key_dim, self.head_dim))
kv_scale = jnp.ones((bsz, self.num_heads, 1, 1))
for i in range(num_chunks):
kv_recurrent.append(kv_state / kv_scale)
cross_scale.append(kv_scale)
kv_state = kv_state * cross_decay + kv[:, i]
kv_scale = (
jnp.abs(jax.lax.stop_gradient(kv_state).sum(axis=-2, keepdims=True))
.max(axis=-1, keepdims=True)
.clip(min=1)
)
kv_recurrent = jnp.stack(kv_recurrent, axis=1)
cross_scale = jnp.stack(cross_scale, axis=1)
all_scale = jnp.maximum(inner_scale, cross_scale)
align_inner_scale = all_scale / inner_scale
align_cross_scale = all_scale / cross_scale
cross_output = (qr * inner_decay) @ kv_recurrent
output = inner_output / align_inner_scale + cross_output / align_cross_scale
output = output.transpose((0, 2, 1, 3, 4))
return output
def __call__(
self,
hidden_states: jnp.ndarray,
rel_pos: Optional[jnp.ndarray] = None,
chunkwise_recurrent: bool = True,
incremental_state=None,
) -> jnp.ndarray:
bsz, tgt_len, _ = hidden_states.shape
(sin, cos), inner_mask = rel_pos
q = self.q_proj(hidden_states)
k = self.k_proj(hidden_states)
v = self.v_proj(hidden_states)
g = self.g_proj(hidden_states)
k *= self.scaling
q = q.reshape(bsz, tgt_len, self.num_heads, self.key_dim).transpose(
(0, 2, 1, 3)
)
k = k.reshape(bsz, tgt_len, self.num_heads, self.key_dim).transpose(
(0, 2, 1, 3)
)
qr = theta_shift(q, sin, cos)
kr = theta_shift(k, sin, cos)
if incremental_state is not None:
raise NotImplementedError
elif self.config.attention_type == "chunkwise_recurrent":
output = self.chunk_recurrent_forward(qr, kr, v, inner_mask=inner_mask)
else:
output = self.parallel_forward(qr, kr, v, inner_mask)
output = self.group_norm(output)
output = output.reshape(bsz, tgt_len, -1)
output = nn.swish(g) * output
output = self.out_proj(output)
return output
class FlaxRetNetLayer(nn.Module):
config: RetNetConfig
dtype: jnp.dtype = jnp.float32
def setup(self) -> None:
self.retention = FlaxRetNetRetention(self.config, dtype=self.dtype)
self.retention_layer_norm = nn.LayerNorm(
epsilon=self.config.layer_norm_eps, dtype=self.dtype
)
self.ffn = FlaxRetNetFeedForward(self.config, dtype=self.dtype)
self.final_layer_norm = nn.LayerNorm(
epsilon=self.config.layer_norm_eps, dtype=self.dtype
)
self.dropout_module = nn.Dropout(rate=self.config.dropout)
def __call__(
self,
hidden_states: jnp.ndarray,
retention_rel_pos: Optional[tuple] = None,
deterministic: bool = True,
) -> jnp.ndarray:
residual = hidden_states
hidden_states = self.retention_layer_norm(hidden_states)
hidden_states = self.retention(hidden_states, rel_pos=retention_rel_pos)
hidden_states = self.dropout_module(hidden_states, deterministic=deterministic)
hidden_states = residual + hidden_states
residual = hidden_states
hidden_states = self.final_layer_norm(hidden_states)
hidden_states = self.ffn(hidden_states, deterministic=deterministic)
hidden_states = residual + hidden_states
return hidden_states
class FlaxRetNetLayerCollection(nn.Module):
config: RetNetConfig
dtype: jnp.dtype = jnp.float32
def setup(self) -> None:
self.layers = [
FlaxRetNetLayer(self.config, dtype=self.dtype)
for _ in range(self.config.num_hidden_layers)
]
def __call__(
self,
hidden_states: jnp.ndarray,
retention_rel_pos: tuple = None,
deterministic: bool = True,
output_retentions: bool = False,
output_hidden_states: bool = False,
return_dict: bool = True,
) -> jnp.ndarray:
all_hidden_states = () if output_hidden_states else None
all_retentions = () if output_retentions else None
for layer in self.layers:
if output_hidden_states:
all_hidden_states += (hidden_states,)
layer_outputs = layer(
hidden_states,
retention_rel_pos=retention_rel_pos,
deterministic=deterministic,
)
hidden_states = layer_outputs
outputs = (hidden_states, all_hidden_states, all_retentions)
return outputs
class FlaxRetNetPretrainedModel(FlaxPreTrainedModel):
config_class = RetNetConfig
base_model_prefix = "transformer"
main_input_name = "input_ids"
module_class: nn.Module = None
def __init__(
self,
config: RetNetConfig,
input_shape: Tuple = (1, 1),
seed: int = 0,
dtype: jnp.dtype = jnp.float32,
_do_init: bool = True,
**kwargs
):
module = self.module_class(config, dtype=dtype, **kwargs)
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:
input_ids = jnp.zeros(input_shape, dtype="i4")
attention_mask = jnp.ones_like(input_ids)
params_rng, dropout_rng = jax.random.split(rng)
rngs = {"params": params_rng, "dropout": dropout_rng}
module_init_outputs = self.module.init(
rngs, input_ids, attention_mask, return_dict=False
)
random_params = module_init_outputs["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 = []
return freeze(unflatten_dict(params))
else:
return random_params
def __call__(
self,
input_ids: jnp.ndarray,
attention_mask: Optional[jnp.ndarray] = None,
params: dict = None,
dropout_rng: jnp.ndarray = None,
train: bool = False,
output_retentions: bool = False,
output_hidden_states: bool = False,
return_dict: bool = True,
):
output_retentions = (
output_retentions
if output_retentions is not None
else self.config.output_retentions
)
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 attention_mask is None:
attention_mask = jnp.ones((batch_size, sequence_length))
rngs = {}
if dropout_rng is not None:
rngs["dropout"] = dropout_rng
inputs = {"params": params or self.params}
outputs = self.module.apply(
inputs,
jnp.array(input_ids, dtype="i4"),
jnp.array(attention_mask, dtype="i4"),
not train,
output_retentions,
output_hidden_states,
return_dict,
rngs=rngs,
)
return outputs
class FlaxRetNetModule(nn.Module):
config: RetNetConfig
dtype: jnp.dtype = jnp.float32
def setup(self) -> None:
self.embed_tokens = nn.Embed(
self.config.vocab_size,
self.config.hidden_size,
embedding_init=jax.nn.initializers.xavier_normal(),
dtype=self.dtype,
)
self.retnet_rel_pos = FlaxRetNetRelPos(self.config, dtype=self.dtype)
self.layers = FlaxRetNetLayerCollection(self.config, dtype=self.dtype)
def __call__(
self,
input_ids: jnp.ndarray,
attention_mask: Optional[jnp.ndarray] = None,
deterministic: bool = True,
output_retentions: bool = False,
output_hidden_states: bool = False,
return_dict: bool = True,
):
input_embeds = self.embed_tokens(input_ids)
batch_size, sequence_length = input_embeds.shape[:2]
retention_rel_pos = self.retnet_rel_pos(
sequence_length,
activate_recurrent=False,
chunkwise_recurrent=self.config.attention_type == "chunkwise_recurrent",
)
outputs = self.layers(
input_embeds,
retention_rel_pos=retention_rel_pos,
deterministic=deterministic,
output_retentions=output_retentions,
output_hidden_states=output_hidden_states,
return_dict=return_dict,
)
if not return_dict:
return tuple(v for v in outputs if v is not None)
return FlaxBaseModelOutput(
last_hidden_state=outputs[0],
hidden_states=outputs[1],
attentions=outputs[-1],
)
class FlaxRetNetModel(FlaxRetNetPretrainedModel):
module_class = FlaxRetNetModule
class FlaxRetNetForCausalLMModule(nn.Module):
config: RetNetConfig
dtype: jnp.dtype = jnp.float32
def setup(self) -> None:
self.transformer = FlaxRetNetModule(self.config, dtype=self.dtype)
self.lm_head = nn.Dense(
self.config.vocab_size,
use_bias=False,
kernel_init=jax.nn.initializers.normal(self.config.initializer_range),
dtype=self.dtype,
)
def __call__(
self,
input_ids: jnp.ndarray,
attention_mask: Optional[jnp.ndarray] = None,
deterministic: bool = True,
output_retentions: bool = False,
output_hidden_states: bool = False,
return_dict: bool = True,
):
outputs = self.transformer(
input_ids,
attention_mask=attention_mask,
deterministic=deterministic,
output_retentions=output_retentions,
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 FlaxRetNetForCausalLM(FlaxRetNetPretrainedModel):
module_class = FlaxRetNetForCausalLMModule
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