# Copyright (c) Microsoft Corporation. # Licensed under the MIT license. # # Copyright (c) 2022, Tri Dao, trid@cs.stanford.edu. # Licensed under the BSD 3-Clause License. from __future__ import annotations import math from dataclasses import dataclass, field from typing import Any, Dict, Optional, Tuple, Union import torch import torch.nn as nn from einops import rearrange, repeat from transformers import PretrainedConfig, PreTrainedModel from transformers.activations import ACT2FN from transformers.modeling_outputs import CausalLMOutputWithPast from .configuration_phi import PhiConfig try: from flash_attn.bert_padding import pad_input, unpad_input from flash_attn.layers.rotary import RotaryEmbedding as FlashRotaryEmbedding from flash_attn.modules.mha import FlashCrossAttention, FlashSelfAttention from flash_attn.ops.fused_dense import FusedDense except: pad_input, unpad_input = None, None FlashRotaryEmbedding = None FlashSelfAttention, FlashCrossAttention = None, None FusedDense = None @dataclass class InferenceParams: """Inference parameters passed to model to efficiently calculate and store context during inference. Reference: https://github.com/Dao-AILab/flash-attention/blob/main/flash_attn/utils/generation.py. Args: max_seqlen: Maximum sequence length. max_batch_size: Maximum batch size. seqlen_offset: Sequence length offset. batch_size_offset: Batch size offset. key_value_memory_dict: Key value memory dictionary. lengths_per_sample: Lengths per sample. """ max_seqlen: int = field(metadata={"help": "Maximum sequence length."}) max_batch_size: int = field(metadata={"help": "Maximum batch size."}) seqlen_offset: int = field(default=0, metadata={"help": "Sequence length offset."}) batch_size_offset: int = field(default=0, metadata={"help": "Batch size offset."}) key_value_memory_dict: Dict[str, Any] = field( default_factory=dict, metadata={"help": "Key value memory dictionary."} ) lengths_per_sample: torch.Tensor = field(default=None, metadata={"help": "Lengths per sample."}) class Embedding(nn.Module): """Token embedding with dropout.""" def __init__(self, config: PretrainedConfig) -> None: super().__init__() self.wte = nn.Embedding(config.vocab_size, config.n_embd) self.drop = nn.Dropout(config.embd_pdrop) def forward(self, input_ids: torch.LongTensor) -> torch.FloatTensor: input_shape = input_ids.size() input_ids = input_ids.view(-1, input_shape[-1]) hidden_states = self.wte(input_ids) hidden_states = self.drop(hidden_states) return hidden_states def _apply_rotary_emb( x: torch.FloatTensor, cos: torch.FloatTensor, sin: torch.FloatTensor, ) -> torch.FloatTensor: _, seqlen, _, _ = x.shape _, rotary_dim = cos.shape rotary_dim *= 2 x_rot = x[:, :, :, :rotary_dim] x_pass = x[:, :, :, rotary_dim:] x1, x2 = x_rot.chunk(2, dim=-1) c, s = rearrange(cos[:seqlen], "s d -> s 1 d"), rearrange(sin[:seqlen], "s d -> s 1 d") x1, x2, c, s = [t.to(dtype=torch.float32) for t in [x1, x2, c, s]] x_rot = torch.cat([x1 * c - x2 * s, x1 * s + x2 * c], axis=-1).to(x.dtype) return torch.cat([x_rot, x_pass], axis=-1) def _apply_rotary_emb_kv( kv: torch.FloatTensor, cos: torch.FloatTensor, sin: torch.FloatTensor, cos_k: Optional[torch.FloatTensor] = None, sin_k: Optional[torch.FloatTensor] = None, ) -> torch.FloatTensor: _, seqlen, _, _, _ = kv.shape _, rotary_dim = cos.shape rotary_dim *= 2 k_rot = kv[:, :, 0, :, :rotary_dim] k_pass = kv[:, :, 0, :, rotary_dim:] k1, k2 = k_rot.chunk(2, dim=-1) c, s = rearrange(cos[:seqlen], "s d -> s 1 d"), rearrange(sin[:seqlen], "s d -> s 1 d") k1, k2, c, s = [t.to(dtype=torch.float32) for t in [k1, k2, c, s]] k_rot = torch.cat([k1 * c - k2 * s, k1 * s + k2 * c], axis=-1).to(kv.dtype) return torch.cat( [ torch.cat([k_rot, k_pass], axis=-1).unsqueeze(2), kv[:, :, 1:2, :, :], ], axis=2, ) def _apply_rotary_emb_qkv( qkv: torch.FloatTensor, cos: torch.FloatTensor, sin: torch.FloatTensor, cos_k: Optional[torch.FloatTensor] = None, sin_k: Optional[torch.FloatTensor] = None, ) -> torch.FloatTensor: _, seqlen, _, _, _ = qkv.shape _, rotary_dim = cos.shape rotary_dim *= 2 q_rot = qkv[:, :, 0, :, :rotary_dim] q_pass = qkv[:, :, 0, :, rotary_dim:] k_rot = qkv[:, :, 1, :, :rotary_dim] k_pass = qkv[:, :, 1, :, rotary_dim:] q1, q2 = q_rot.chunk(2, dim=-1) k1, k2 = k_rot.chunk(2, dim=-1) c, s = rearrange(cos[:seqlen], "s d -> s 1 d"), rearrange(sin[:seqlen], "s d -> s 1 d") q1, q2, k1, k2, c, s = [t.to(dtype=torch.float32) for t in [q1, q2, k1, k2, c, s]] q_rot = torch.cat([q1 * c - q2 * s, q1 * s + q2 * c], axis=-1).to(qkv.dtype) k_rot = torch.cat([k1 * c - k2 * s, k1 * s + k2 * c], axis=-1).to(qkv.dtype) return torch.cat( [ torch.cat([q_rot, q_pass], axis=-1).unsqueeze(2), torch.cat([k_rot, k_pass], axis=-1).unsqueeze(2), qkv[:, :, 2:3, :, :], ], axis=2, ) class RotaryEmbedding(nn.Module): """Rotary positional embedding (RoPE). Reference: RoFormer: Enhanced Transformer with Rotary Position Embedding. https://arxiv.org/pdf/2104.09864.pdf. """ def __init__( self, dim: int, base: int = 10000, scale_base: Optional[float] = None, pos_idx_in_fp32: bool = True, max_position_embeddings: int = 2048, device: Optional[str] = None, **kwargs, ) -> None: super().__init__() if scale_base is not None: raise NotImplementedError self.dim = dim self.base = float(base) self.scale_base = scale_base self.pos_idx_in_fp32 = pos_idx_in_fp32 self.max_position_embeddings = max_position_embeddings self.device = device # Generate and save the inverse frequency buffer (non-trainable) inv_freq = self._compute_inv_freq(device) self.register_buffer("inv_freq", inv_freq, persistent=False) # Generate and save the scale buffer (non-trainable) scale = ( (torch.arange(0, dim, 2, device=device, dtype=torch.float32) + 0.4 * dim) / (1.4 * dim) if scale_base is not None else None ) self.register_buffer("scale", scale, persistent=False) # Initialize cached attributes since ONNX can't rely on dynamic initialization self._update_cos_sin_cache(max_position_embeddings, device=device, dtype=torch.float32) def _compute_inv_freq(self, device: Optional[str] = None) -> torch.FloatTensor: return 1.0 / (self.base ** (torch.arange(0, self.dim, 2, device=device, dtype=torch.float32) / self.dim)) def _update_cos_sin_cache( self, seqlen: int, device: Optional[str] = None, dtype: Optional[torch.dtype] = None, ) -> None: self._seq_len_cached = seqlen # fp32 is preferred since the output of `torch.arange` can be quite large # and bf16 would lose a lot of precision if self.pos_idx_in_fp32: t = torch.arange(seqlen, device=device, dtype=torch.float32) if self.inv_freq.dtype != torch.float32: inv_freq = self._compute_inv_freq(device=device) else: inv_freq = self.inv_freq else: t = torch.arange(seqlen, device=device, dtype=self.inv_freq.dtype) inv_freq = self.inv_freq # `torch.outer` is preferred since `torch.einsum` converts from fp32 to fp16 if used with AMP freqs = torch.outer(t, inv_freq) if self.scale is None: self._cos_cached = torch.cos(freqs).to(dtype) self._sin_cached = torch.sin(freqs).to(dtype) else: power = ( torch.arange(seqlen, dtype=self.scale.dtype, device=self.scale.device) - seqlen // 2 ) / self.scale_base scale = self.scale.to(device=power.device) ** rearrange(power, "s -> s 1") # Force the scale multiplication to happen in fp32 self._cos_cached = (torch.cos(freqs) * scale).to(dtype) self._sin_cached = (torch.sin(freqs) * scale).to(dtype) self._cos_k_cached = (torch.cos(freqs) / scale).to(dtype) self._sin_k_cached = (torch.sin(freqs) / scale).to(dtype) def forward( self, qkv: torch.Tensor, kv: Optional[torch.Tensor] = None, seqlen_offset: int = 0, **kwargs, ) -> Tuple[torch.Tensor, torch.Tensor]: seq_start = seqlen_offset seq_end = seq_start + qkv.shape[1] if ( self._cos_cached.device != qkv.device or self._cos_cached.dtype != qkv.dtype or (self.training and self._cos_cached.is_inference()) ): self._update_cos_sin_cache(self.max_position_embeddings, device=qkv.device, dtype=qkv.dtype) if kv is None: return _apply_rotary_emb_qkv( qkv, self._cos_cached[seq_start:seq_end], self._sin_cached[seq_start:seq_end], ) else: q = _apply_rotary_emb( qkv, self._cos_cached[seq_start:seq_end], self._sin_cached[seq_start:seq_end], ) kv = _apply_rotary_emb_kv( kv, self._cos_cached[seq_start:seq_end], self._sin_cached[seq_start:seq_end], ) return q, kv class MLP(nn.Module): """Multi-Layer Perceptron. Reference: Attention Is All You Need. https://arxiv.org/pdf/1706.03762.pdf. """ def __init__( self, config: PretrainedConfig, n_inner: Optional[int] = None, act_fn: Optional[str] = None, ) -> None: super().__init__() act_fn = config.activation_function if act_fn is None else act_fn n_inner = getattr(config, "n_inner", None) if n_inner is None else n_inner n_inner = n_inner if n_inner is not None else 4 * config.n_embd self.fc1 = nn.Linear(config.n_embd, n_inner) self.fc2 = nn.Linear(n_inner, config.n_embd) self.act = ACT2FN[act_fn] def forward(self, hidden_states: torch.FloatTensor) -> torch.FloatTensor: hidden_states = self.fc1(hidden_states) hidden_states = self.act(hidden_states) hidden_states = self.fc2(hidden_states) return hidden_states class SelfAttention(nn.Module): """Self-attention layer (compatible with PyTorch). Reference: https://github.com/Dao-AILab/flash-attention/blob/main/flash_attn/modules/mha.py. """ def __init__( self, causal: bool = True, softmax_scale: Optional[float] = None, attention_dropout: float = 0.0, ) -> None: super().__init__() self.causal = causal self.softmax_scale = softmax_scale self.drop = nn.Dropout(attention_dropout) @torch.autocast("cpu", enabled=False) @torch.autocast("cuda", enabled=False) def forward( self, qkv: torch.FloatTensor, causal: bool = None, key_padding_mask: Optional[torch.BoolTensor] = None, **kwargs, ) -> torch.FloatTensor: batch_size, seqlen = qkv.shape[0], qkv.shape[1] q, k, v = qkv.unbind(dim=2) q = q.to(torch.float32) k = k.to(torch.float32) causal = self.causal if causal is None else causal softmax_scale = self.softmax_scale or 1.0 / math.sqrt(q.shape[-1]) # Autocast is manually disabled to avoid `torch.einsum` performing the operation # using float16, which might lead to overflow scores = torch.einsum("bthd,bshd->bhts", q, k * softmax_scale) if key_padding_mask is not None: padding_mask = torch.full((batch_size, seqlen), -10000.0, dtype=scores.dtype, device=scores.device) padding_mask.masked_fill_(key_padding_mask, 0.0) scores = scores + rearrange(padding_mask, "b s -> b 1 1 s") if causal: causal_mask = torch.triu(torch.full((seqlen, seqlen), -10000.0, device=scores.device), 1) scores = scores + causal_mask.to(dtype=scores.dtype) attention = torch.softmax(scores, dim=-1).to(v.dtype) attention = self.drop(attention) output = torch.einsum("bhts,bshd->bthd", attention, v) return output class CrossAttention(nn.Module): """Cross-attention layer (compatible with PyTorch). Reference: https://github.com/Dao-AILab/flash-attention/blob/main/flash_attn/modules/mha.py. """ def __init__( self, causal: bool = True, softmax_scale: Optional[float] = None, attention_dropout: float = 0.0, ) -> None: super().__init__() self.causal = causal self.softmax_scale = softmax_scale self.drop = nn.Dropout(attention_dropout) @torch.autocast("cpu", enabled=False) @torch.autocast("cuda", enabled=False) def forward( self, q: torch.FloatTensor, kv: torch.FloatTensor, causal: bool = None, key_padding_mask: Optional[torch.BoolTensor] = None, **kwargs, ) -> torch.FloatTensor: batch_size, seqlen_q = q.shape[0], q.shape[1] seqlen_k = kv.shape[1] if kv.shape[3] != q.shape[2]: kv = repeat(kv, "... hkv d -> ... (hkv g) d", g=q.shape[2] // kv.shape[3]) k, v = kv.unbind(dim=2) q = q.to(torch.float32) k = k.to(torch.float32) causal = self.causal if causal is None else causal softmax_scale = self.softmax_scale or 1.0 / math.sqrt(q.shape[-1]) # Autocast is manually disabled to avoid `torch.einsum` performing the operation # using float16, which might lead to overflow scores = torch.einsum("bthd,bshd->bhts", q, k * softmax_scale) if key_padding_mask is not None: padding_mask = torch.full( (batch_size, seqlen_k), -10000.0, dtype=scores.dtype, device=scores.device, ) padding_mask.masked_fill_(key_padding_mask, 0.0) scores = scores + rearrange(padding_mask, "b s -> b 1 1 s") if causal: rows = rearrange(torch.arange(seqlen_q, device=q.device, dtype=torch.long), "s -> s 1") cols = torch.arange(seqlen_k, device=k.device, dtype=torch.long) causal_mask = cols > rows + seqlen_k - seqlen_q scores = scores.masked_fill(causal_mask, -10000.0) attention = torch.softmax(scores, dim=-1).to(v.dtype) attention = self.drop(attention) output = torch.einsum("bhts,bshd->bthd", attention, v) return output def _find_mha_dims( config: PretrainedConfig, n_head: Optional[int] = None, n_head_kv: Optional[int] = None, head_dim: Optional[int] = None, ) -> Tuple[int, int]: if n_head is None and head_dim is None: head_dim = config.n_embd // config.n_head n_head = config.n_head elif n_head is None or head_dim is None: raise ValueError("`n_head` and `head_dim` must be both specified or `None`.") if n_head_kv is None: n_head_kv = getattr(config, "n_head_kv", None) or n_head return n_head, n_head_kv, head_dim def _update_kv_cache(kv: torch.FloatTensor, inference_params: InferenceParams, layer_idx: int) -> torch.FloatTensor: num_heads, head_dim = kv.shape[-2:] if layer_idx not in inference_params.key_value_memory_dict: inference_params.key_value_memory_dict[layer_idx] = torch.empty( inference_params.max_batch_size, inference_params.max_seqlen, 2, num_heads, head_dim, dtype=kv.dtype, device=kv.device, ) batch_start = inference_params.batch_size_offset batch_end = batch_start + kv.shape[0] sequence_start = inference_params.seqlen_offset sequence_end = sequence_start + kv.shape[1] # When the current sequence length is equal to or larger than the maximum sequence length, # we need to roll the cache to the left and update it if sequence_end >= inference_params.max_seqlen: inference_params.key_value_memory_dict[layer_idx] = inference_params.key_value_memory_dict[layer_idx].roll(-(sequence_end - sequence_start), 1) inference_params.key_value_memory_dict[layer_idx][batch_start:batch_end, sequence_start:sequence_end, ...] = kv kv = inference_params.key_value_memory_dict[layer_idx][batch_start:batch_end, :sequence_end, ...] return kv class MHA(nn.Module): """Multi-head attention layer.""" def __init__( self, config: PretrainedConfig, dtype: Optional[torch.dtype] = None, device: Optional[str] = None, rotary_dim: Optional[int] = None, rotary_base: float = 10000.0, rotary_scale_base: Optional[float] = None, n_head: Optional[int] = None, n_head_kv: Optional[int] = None, head_dim: Optional[int] = None, bias: bool = True, causal: bool = True, softmax_scale: Optional[float] = None, layer_idx: Optional[int] = None, return_residual: bool = False, checkpointing: bool = False, ) -> None: super().__init__() # Rotary embedding self.rotary_dim = rotary_dim if rotary_dim is not None else getattr(config, "rotary_dim", 0) if self.rotary_dim > 0: rotary_cls = FlashRotaryEmbedding if config.flash_rotary else RotaryEmbedding if rotary_cls is None: rotary_cls = RotaryEmbedding rotary_kwargs = {} if rotary_cls is RotaryEmbedding: rotary_kwargs["max_position_embeddings"] = config.n_positions self.rotary_emb = rotary_cls( self.rotary_dim, base=rotary_base, scale_base=rotary_scale_base, device=device, **rotary_kwargs, ) # MLP self.n_head, self.n_head_kv, self.head_dim = _find_mha_dims( config, n_head=n_head, n_head_kv=n_head_kv, head_dim=head_dim ) op_size = self.head_dim * (self.n_head + 2 * self.n_head_kv) hidden_size = config.n_embd linear_cls = FusedDense if config.fused_dense else nn.Linear if linear_cls is None: linear_cls = nn.Linear self.Wqkv = linear_cls(hidden_size, op_size, bias=bias, device=device, dtype=dtype) self.out_proj = linear_cls(hidden_size, hidden_size, bias=bias, device=device, dtype=dtype) # Attention attn_cls = FlashSelfAttention if config.flash_attn else SelfAttention if attn_cls is None: attn_cls = SelfAttention cross_attn_cls = FlashCrossAttention if config.flash_attn else CrossAttention if cross_attn_cls is None: cross_attn_cls = CrossAttention self.inner_attn = attn_cls( causal=causal, softmax_scale=softmax_scale, attention_dropout=config.attn_pdrop, ) self.inner_cross_attn = cross_attn_cls( causal=causal, softmax_scale=softmax_scale, attention_dropout=config.attn_pdrop, ) self.flash_attn = config.flash_attn and attn_cls is FlashSelfAttention self.layer_idx = layer_idx self.return_residual = return_residual self.checkpointing = checkpointing def _forward_self_attn( self, x: torch.FloatTensor, key_padding_mask: Optional[torch.BoolTensor] ) -> torch.FloatTensor: qkv = self.Wqkv(x) qkv = rearrange(qkv, "... (three h d) -> ... three h d", three=3, d=self.head_dim) if self.rotary_dim > 0: qkv = self.rotary_emb(qkv) if self.flash_attn: batch_size, seqlen = qkv.shape[0], qkv.shape[1] cu_seqlens, max_seqlen = None, None if key_padding_mask is not None: # If `key_padding_mask` is supplied, we need to unpad the input and retrieve # the `cu_seqlens` and `max_seqlen` to be used by `flash-attn` qkv, indices, cu_seqlens, max_seqlen = unpad_input(qkv, key_padding_mask) if self.checkpointing: attn_output = torch.utils.checkpoint.checkpoint( self.inner_attn, qkv, cu_seqlens=cu_seqlens, max_seqlen=max_seqlen ) else: attn_output = self.inner_attn(qkv, cu_seqlens=cu_seqlens, max_seqlen=max_seqlen).to(qkv.device) # If `key_padding_mask` is supplied, we need to pad the output back to the original shape return pad_input(attn_output, indices, batch_size, seqlen) if key_padding_mask is not None else attn_output if self.checkpointing: return torch.utils.checkpoint.checkpoint(self.inner_attn, qkv, key_padding_mask=key_padding_mask) return self.inner_attn(qkv, key_padding_mask=key_padding_mask) def _forward_cross_attn( self, x: torch.FloatTensor, past_key_values: Optional[InferenceParams], key_padding_mask: Optional[torch.BoolTensor], ) -> torch.FloatTensor: batch_size = x.shape[0] qkv = self.Wqkv(x) q = qkv[..., : self.n_head * self.head_dim] q = rearrange(q, "... (h d) -> ... h d", d=self.head_dim) kv = qkv[..., self.n_head * self.head_dim :] kv = rearrange(kv, "... (two hkv d) -> ... two hkv d", two=2, d=self.head_dim) seqlen_offset = past_key_values.seqlen_offset if past_key_values is not None else 0 causal = None if seqlen_offset == 0 else False if self.rotary_dim > 0: q, kv = self.rotary_emb(q, kv=kv, seqlen_offset=seqlen_offset) if past_key_values is not None: kv = _update_kv_cache(kv, past_key_values, self.layer_idx) if self.flash_attn: batch_size, seqlen_q = q.shape[0], q.shape[1] seqlen_k = kv.shape[1] cu_seqlens_q, cu_seqlens_k, max_seqlen_q, max_seqlen_k = ( None, None, None, None, ) if key_padding_mask is not None: kv, _, cu_seqlens_k, max_seqlen_k = unpad_input(kv, key_padding_mask) if seqlen_q == 1: key_padding_mask = torch.ones(batch_size, 1, device=q.device) elif seqlen_q != seqlen_k: key_padding_mask = key_padding_mask[:, -seqlen_q:] q, indices_q, cu_seqlens_q, max_seqlen_q = unpad_input(q, key_padding_mask) if self.checkpointing: attn_output = torch.utils.checkpoint.checkpoint( self.inner_cross_attn, q, kv, causal=causal, cu_seqlens=cu_seqlens_q, max_seqlen=max_seqlen_q, cu_seqlens_k=cu_seqlens_k, max_seqlen_k=max_seqlen_k, ) else: attn_output = self.inner_cross_attn( q, kv, causal=causal, cu_seqlens=cu_seqlens_q, max_seqlen=max_seqlen_q, cu_seqlens_k=cu_seqlens_k, max_seqlen_k=max_seqlen_k, ) return ( pad_input(attn_output, indices_q, batch_size, max_seqlen_q) if key_padding_mask is not None else attn_output ) if self.checkpointing: return torch.utils.checkpoint.checkpoint( self.inner_cross_attn, q, kv, key_padding_mask=key_padding_mask, causal=causal, ) return self.inner_cross_attn(q, kv, key_padding_mask=key_padding_mask, causal=causal) def forward( self, x: torch.FloatTensor, past_key_values: Optional[InferenceParams] = None, attention_mask: Optional[Union[torch.LongTensor, torch.BoolTensor]] = None, **kwargs, ) -> Tuple[torch.FloatTensor, torch.FloatTensor]: if attention_mask is not None: attention_mask = attention_mask.bool() else: attention_mask = None # MHA if self.n_head == self.n_head_kv: if past_key_values is None: # If `past_key_values` are not supplied, we run self-attention attn_output = self._forward_self_attn(x, attention_mask) else: # If `past_key_values` are supplied, it means that we might have cached values and # could take advantage of cross-attention attn_output = self._forward_cross_attn(x, past_key_values, attention_mask) # MQA / GQA else: # Regardless of `past_key_values` being supplied or not, it always use cross-attention # because `q` and `kv` lengths might be different attn_output = self._forward_cross_attn(x, past_key_values, attention_mask) output = rearrange(attn_output, "... h d -> ... (h d)") output = self.out_proj(output) return output if not self.return_residual else (output, x) class ParallelBlock(nn.Module): """Parallel block. This block applies parallel mixer and MLP layers to the input (used in GPT-J and CodeGen). """ def __init__( self, config: PretrainedConfig, block_idx: Optional[int] = None, ) -> None: super().__init__() self.ln = nn.LayerNorm(config.n_embd, eps=config.layer_norm_epsilon) self.resid_dropout = nn.Dropout(config.resid_pdrop) self.block_idx = block_idx if block_idx % 2 == 0: n_inner = 4 * config.n_embd else: n_inner = 1024 self.mixer = MHA(config, layer_idx=block_idx) self.mlp = MLP(config, n_inner) def forward( self, hidden_states: torch.FloatTensor, past_key_values: Optional[Union[torch.FloatTensor, InferenceParams]] = None, attention_mask: Optional[torch.BoolTensor] = None, **kwargs, ) -> torch.FloatTensor: residual = hidden_states hidden_states = self.ln(hidden_states) attn_outputs = self.mixer( hidden_states, past_key_values=past_key_values, attention_mask=attention_mask, ) if isinstance(attn_outputs, tuple): attn_outputs = attn_outputs[0] attn_outputs = self.resid_dropout(attn_outputs) feed_forward_hidden_states = self.resid_dropout(self.mlp(hidden_states)) hidden_states = attn_outputs + feed_forward_hidden_states + residual return hidden_states class CausalLMHead(nn.Module): """Causal Language Modeling head. Reference: Improving Language Understanding by Generative Pre-Training. https://cdn.openai.com/research-covers/language-unsupervised/language_understanding_paper.pdf. """ def __init__(self, config: PretrainedConfig) -> None: super().__init__() self.ln = nn.LayerNorm(config.n_embd, eps=config.layer_norm_epsilon) self.linear = nn.Linear(config.n_embd, config.vocab_size) def forward(self, hidden_states: torch.FloatTensor) -> torch.FloatTensor: hidden_states = self.ln(hidden_states) logits = self.linear(hidden_states).to(torch.float32) return logits class CausalLMLoss(nn.Module): """Causal Language Modeling loss. Reference: Improving Language Understanding by Generative Pre-Training. https://cdn.openai.com/research-covers/language-unsupervised/language_understanding_paper.pdf. """ def __init__(self, shift_labels: bool = True) -> None: super().__init__() self.shift_labels = shift_labels self.loss_fct = nn.CrossEntropyLoss() def forward(self, logits: torch.FloatTensor, labels: torch.LongTensor) -> torch.FloatTensor: if self.shift_labels: logits = logits[..., :-1, :].contiguous() labels = labels[..., 1:].contiguous() loss = self.loss_fct(logits.view(-1, logits.size(-1)), labels.view(-1)) return loss class PhiPreTrainedModel(PreTrainedModel): """Phi pre-trained model.""" config_class = PhiConfig base_model_prefix = "transformer" supports_gradient_checkpointing = False _no_split_modules = ["ParallelBlock"] def __init__(self, *inputs, **kwargs) -> None: super().__init__(*inputs, **kwargs) def _init_weights(self, module: nn.Module) -> None: if isinstance(module, (nn.Linear,)): 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, nn.LayerNorm): if module.bias is not None: module.bias.data.zero_() module.weight.data.fill_(1.0) def prepare_inputs_for_generation( self, input_ids: torch.LongTensor, past_key_values: Optional[Union[torch.FloatTensor, InferenceParams]] = None, attention_mask: Optional[Union[torch.LongTensor, torch.BoolTensor]] = None, **kwargs, ) -> Dict[str, Any]: # Truncate `input_ids` and `attention_mask` (if necessary) to prevent exceeding # the maximum sequence length if input_ids.shape[1] > self.config.n_positions: input_ids = input_ids[:, -self.config.n_positions :] if attention_mask is not None: attention_mask = attention_mask[:, -self.config.n_positions :] if past_key_values is None or not (isinstance(past_key_values, InferenceParams)): past_key_values = InferenceParams( max_seqlen=self.config.n_positions, max_batch_size=input_ids.shape[0], seqlen_offset=0, batch_size_offset=0, key_value_memory_dict={}, lengths_per_sample=None, ) else: # Assume that `past_key_values` has cached all tokens up to the last token in `input_ids` past_key_values.seqlen_offset = input_ids.shape[1] - 1 input_ids = input_ids[:, -1].unsqueeze(-1) return { "input_ids": input_ids, "past_key_values": past_key_values, "attention_mask": attention_mask, } class PhiModel(PhiPreTrainedModel): """Phi model.""" _keys_to_ignore_on_load_missing = [""] _keys_to_ignore_on_load_unexpected = [r"h\.\d+\.mlp.(fc_in|fc_out)\.(weight|bias)"] def __init__(self, config: PhiConfig) -> None: super().__init__(config) self.embd = Embedding(config) self.h = nn.ModuleList([ParallelBlock(config, block_idx=i) for i in range(config.n_layer)]) self.gradient_checkpointing = False self.post_init() def get_input_embeddings(self) -> nn.Embedding: return self.embd.wte def set_input_embeddings(self, new_embeddings: nn.Embedding) -> None: self.embd.wte = new_embeddings def forward( self, input_ids: torch.LongTensor, past_key_values: Optional[Union[torch.FloatTensor, InferenceParams]] = None, attention_mask: Optional[torch.BoolTensor] = None, ) -> torch.FloatTensor: hidden_states = self.embd(input_ids) for layer in self.h: hidden_states = layer( hidden_states, past_key_values=past_key_values, attention_mask=attention_mask, ) return hidden_states class PhiForCausalLM(PhiPreTrainedModel): """Phi for Causal Language Modeling.""" _keys_to_ignore_on_load_missing = [""] _keys_to_ignore_on_load_unexpected = [r"transformer\.h\.\d+\.mlp.(fc_in|fc_out)\.(weight|bias)"] def __init__(self, config: PhiConfig) -> None: super().__init__(config) self.transformer = PhiModel(config) self.lm_head = CausalLMHead(config) self.loss = CausalLMLoss() self.post_init() def get_output_embeddings(self) -> nn.Linear: return self.lm_head.linear def set_output_embeddings(self, new_embeddings: nn.Linear) -> None: self.lm_head.linear = new_embeddings def forward( self, input_ids: torch.LongTensor, past_key_values: Optional[Union[torch.FloatTensor, InferenceParams]] = None, attention_mask: Optional[torch.BoolTensor] = None, labels: Optional[torch.LongTensor] = None, **kwargs, ) -> CausalLMOutputWithPast: hidden_states = self.transformer(input_ids, past_key_values=past_key_values, attention_mask=attention_mask) lm_logits = self.lm_head(hidden_states) loss = None if labels is not None: loss = self.loss(lm_logits, labels) return CausalLMOutputWithPast(loss=loss, logits=lm_logits, past_key_values=past_key_values)