Tokle-3M / modeling_tokle.py
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"""Tokle: decoder-only transformer with RMSNorm, RoPE, GQA and SwiGLU.
Module and parameter names follow the usual Transformers layout.
Works on Transformers 4.x and 5.x; the v5 differences are marked inline.
"""
import math
from typing import Optional, Tuple, Union
import torch
import torch.nn as nn
import torch.nn.functional as F
from transformers import __version__ as _transformers_version
from transformers.generation import GenerationMixin
from transformers.modeling_outputs import BaseModelOutput, CausalLMOutput
from transformers.modeling_utils import PreTrainedModel
try: # as a Transformers dynamic module (trust_remote_code)
from .configuration_tokle import TokleConfig
except ImportError: # running the files straight out of a checkout
from configuration_tokle import TokleConfig
# ----------------------------------------------------------------------------- norms and rope
class TokleRMSNorm(nn.Module):
def __init__(self, d, eps=1e-5):
super().__init__()
self.eps = eps
self.weight = nn.Parameter(torch.ones(d))
def forward(self, x):
# Always reduce in fp32: in fp16 the mean of squares underflows on the
# long tail and the norm comes back slightly wrong.
dt = x.dtype
x = x.float()
x = x * torch.rsqrt(x.pow(2).mean(-1, keepdim=True) + self.eps)
return (x * self.weight.float()).to(dt)
def extra_repr(self):
return f"{tuple(self.weight.shape)}, eps={self.eps}"
def build_rope(head_dim, max_seq_len, theta, device=None):
inv = 1.0 / (theta ** (torch.arange(0, head_dim, 2, dtype=torch.float32,
device=device) / head_dim))
t = torch.arange(max_seq_len, dtype=torch.float32, device=device)
f = torch.outer(t, inv)
return torch.cos(f), torch.sin(f)
def apply_rope(x, cos, sin):
"""Half-split rotation (first half against second), not the interleaved
variant. The two are not interchangeable -- swapping them degrades output
without raising anything."""
b, h, t, d = x.shape
x1, x2 = x.float().chunk(2, dim=-1)
c = cos[:t].view(1, 1, t, d // 2).to(x1.device)
s = sin[:t].view(1, 1, t, d // 2).to(x1.device)
return torch.cat([x1 * c - x2 * s, x1 * s + x2 * c], dim=-1).to(x.dtype)
# ----------------------------------------------------------------------------- blocks
class TokleAttention(nn.Module):
def __init__(self, config: TokleConfig, layer_idx: int):
super().__init__()
self.layer_idx = layer_idx
self.n_head = config.n_head
self.n_kv_head = config.n_kv_head
self.head_dim = config.head_dim
self.rep = config.n_head // config.n_kv_head
self.q_proj = nn.Linear(config.d_model, config.n_head * config.head_dim, bias=False)
self.k_proj = nn.Linear(config.d_model, config.n_kv_head * config.head_dim, bias=False)
self.v_proj = nn.Linear(config.d_model, config.n_kv_head * config.head_dim, bias=False)
self.o_proj = nn.Linear(config.n_head * config.head_dim, config.d_model, bias=False)
self.q_norm = TokleRMSNorm(config.head_dim, config.norm_eps)
self.k_norm = TokleRMSNorm(config.head_dim, config.norm_eps)
def forward(self, x, cos, sin, attn_mask):
b, t, _ = x.shape
q = self.q_proj(x).view(b, t, self.n_head, self.head_dim).transpose(1, 2)
k = self.k_proj(x).view(b, t, self.n_kv_head, self.head_dim).transpose(1, 2)
v = self.v_proj(x).view(b, t, self.n_kv_head, self.head_dim).transpose(1, 2)
# QK-norm is applied before rope.
q = apply_rope(self.q_norm(q), cos, sin)
k = apply_rope(self.k_norm(k), cos, sin)
k = k.repeat_interleave(self.rep, dim=1)
v = v.repeat_interleave(self.rep, dim=1)
if attn_mask is None:
# Nothing padded: let SDPA build the causal mask itself, which is
# the fast kernel path and what an unpadded forward always hits.
o = F.scaled_dot_product_attention(q, k, v, is_causal=True)
else:
o = F.scaled_dot_product_attention(q, k, v, attn_mask=attn_mask.to(q.dtype))
return self.o_proj(o.transpose(1, 2).reshape(b, t, -1))
class TokleMLP(nn.Module):
def __init__(self, config: TokleConfig):
super().__init__()
self.gate_proj = nn.Linear(config.d_model, config.ffn_hidden, bias=False)
self.up_proj = nn.Linear(config.d_model, config.ffn_hidden, bias=False)
self.down_proj = nn.Linear(config.ffn_hidden, config.d_model, bias=False)
def forward(self, x):
return self.down_proj(F.silu(self.gate_proj(x)) * self.up_proj(x))
class TokleDecoderLayer(nn.Module):
def __init__(self, config: TokleConfig, layer_idx: int):
super().__init__()
self.input_layernorm = TokleRMSNorm(config.d_model, config.norm_eps)
self.self_attn = TokleAttention(config, layer_idx)
self.post_attention_layernorm = TokleRMSNorm(config.d_model, config.norm_eps)
self.mlp = TokleMLP(config)
def forward(self, x, cos, sin, attn_mask):
x = x + self.self_attn(self.input_layernorm(x), cos, sin, attn_mask)
return x + self.mlp(self.post_attention_layernorm(x))
# ----------------------------------------------------------------------------- model
class ToklePreTrainedModel(PreTrainedModel):
config_class = TokleConfig
base_model_prefix = "model"
supports_gradient_checkpointing = True
_no_split_modules = ["TokleDecoderLayer"]
_supports_sdpa = True
def _init_weights(self, module):
if isinstance(module, nn.Linear):
nn.init.normal_(module.weight, 0.0, 0.02)
if module.bias is not None:
nn.init.zeros_(module.bias)
elif isinstance(module, nn.Embedding):
nn.init.normal_(module.weight, 0.0, 0.02)
elif isinstance(module, TokleRMSNorm):
nn.init.ones_(module.weight)
# Residual-output projections get scaled down by depth so the residual
# stream does not blow up at init (GPT-2 trick).
if isinstance(module, (TokleAttention, TokleMLP)):
out = module.o_proj if isinstance(module, TokleAttention) else module.down_proj
nn.init.normal_(out.weight, 0.0, 0.02 / math.sqrt(2 * self.config.n_layer))
class TokleModel(ToklePreTrainedModel):
def __init__(self, config: TokleConfig):
super().__init__(config)
self.embed_tokens = nn.Embedding(config.vocab_size, config.d_model)
self.layers = nn.ModuleList(
[TokleDecoderLayer(config, i) for i in range(config.n_layer)])
self.norm = TokleRMSNorm(config.d_model, config.norm_eps)
# A plain dict, not a buffer. Transformers 5 builds models on the meta
# device and fills only tensors the weights file contains, so a
# non-persistent buffer would come back as uninitialised memory.
# Keyed by device, so .to()/.cuda() need not move anything.
self._rope_cache = {}
self.gradient_checkpointing = False
self.post_init()
def get_input_embeddings(self):
return self.embed_tokens
def set_input_embeddings(self, value):
self.embed_tokens = value
def rope(self, device):
key = str(device)
if key not in self._rope_cache:
self._rope_cache[key] = build_rope(
self.config.head_dim, self.config.max_seq_len,
self.config.rope_theta, device=device)
return self._rope_cache[key]
def _causal_pad_mask(self, attention_mask, t, dtype, device):
"""Additive (b, 1, 1, t) padding mask folded together with the causal
mask, or None when nothing is padded so the caller can take the
is_causal fast path."""
if attention_mask is None:
return None
attention_mask = attention_mask.to(torch.bool)
if bool(attention_mask.all()):
return None
m = torch.zeros(attention_mask.shape, dtype=dtype, device=device)
m = m.masked_fill(~attention_mask, torch.finfo(dtype).min)[:, None, None, :]
# Under causal attention with right padding, position 0 always sees
# itself, so no row ends up fully masked (which would give NaNs).
causal = torch.ones(t, t, dtype=torch.bool, device=device).triu(1)
return m.masked_fill(causal, torch.finfo(dtype).min)
def forward(
self,
input_ids: Optional[torch.LongTensor] = None,
attention_mask: Optional[torch.Tensor] = None,
inputs_embeds: Optional[torch.FloatTensor] = None,
output_hidden_states: Optional[bool] = None,
return_dict: Optional[bool] = None,
**kwargs,
) -> Union[Tuple, BaseModelOutput]:
# getattr, not config.use_return_dict: that property is deprecated in
# Transformers 5 and warns on every call.
return_dict = (return_dict if return_dict is not None
else getattr(self.config, "return_dict", True))
output_hidden_states = (output_hidden_states if output_hidden_states is not None
else self.config.output_hidden_states)
if (input_ids is None) == (inputs_embeds is None):
raise ValueError("Pass exactly one of input_ids or inputs_embeds.")
x = self.embed_tokens(input_ids) if inputs_embeds is None else inputs_embeds
t = x.shape[1]
if t > self.config.max_seq_len:
raise ValueError(
f"Sequence length {t} exceeds max_seq_len {self.config.max_seq_len}.")
cos, sin = self.rope(x.device)
mask = self._causal_pad_mask(attention_mask, t, x.dtype, x.device)
hidden_states = () if output_hidden_states else None
for layer in self.layers:
if output_hidden_states:
hidden_states += (x,)
if self.gradient_checkpointing and self.training:
x = self._gradient_checkpointing_func(layer.__call__, x, cos, sin, mask)
else:
x = layer(x, cos, sin, mask)
x = self.norm(x)
if output_hidden_states:
hidden_states += (x,)
if not return_dict:
return tuple(v for v in (x, hidden_states) if v is not None)
return BaseModelOutput(last_hidden_state=x, hidden_states=hidden_states)
# Transformers 5 turned _tied_weights_keys from a list of names into a
# {tied: source} mapping and calls .keys() on it, so the old form raises.
_TRANSFORMERS_V5 = int(_transformers_version.split(".")[0]) >= 5
class TokleForCausalLM(ToklePreTrainedModel, GenerationMixin):
_tied_weights_keys = ({"lm_head.weight": "model.embed_tokens.weight"}
if _TRANSFORMERS_V5 else ["lm_head.weight"])
def __init__(self, config: TokleConfig):
super().__init__(config)
self.model = TokleModel(config)
self.lm_head = nn.Linear(config.d_model, config.vocab_size, bias=False)
self.post_init()
def get_input_embeddings(self):
return self.model.embed_tokens
def set_input_embeddings(self, value):
self.model.embed_tokens = value
def get_output_embeddings(self):
return self.lm_head
def set_output_embeddings(self, new_embeddings):
self.lm_head = new_embeddings
def get_decoder(self):
return self.model
def forward(
self,
input_ids: Optional[torch.LongTensor] = None,
attention_mask: Optional[torch.Tensor] = None,
inputs_embeds: Optional[torch.FloatTensor] = None,
labels: Optional[torch.LongTensor] = None,
output_hidden_states: Optional[bool] = None,
return_dict: Optional[bool] = None,
**kwargs,
) -> Union[Tuple, CausalLMOutput]:
return_dict = (return_dict if return_dict is not None
else getattr(self.config, "return_dict", True))
out = self.model(
input_ids=input_ids,
attention_mask=attention_mask,
inputs_embeds=inputs_embeds,
output_hidden_states=output_hidden_states,
return_dict=True,
)
logits = self.lm_head(out.last_hidden_state)
# Rows past real_vocab_size only pad the matrix to a multiple of 64 and
# carry no meaning, so keep them out of sampling and out of any
# log-likelihood an evaluation harness sums.
rv = self.config.real_vocab_size
if self.config.mask_padded_vocab_logits and rv is not None and rv < self.config.vocab_size:
logits = logits.clone()
logits[..., rv:] = float("-inf")
loss = None
if labels is not None:
loss = self.loss_function(logits=logits, labels=labels,
vocab_size=self.config.vocab_size, **kwargs)
if not return_dict:
return (loss, logits) if loss is not None else (logits,)
return CausalLMOutput(loss=loss, logits=logits, hidden_states=out.hidden_states)