Support Longchat and RoPE scaling (#555)

Co-authored-by: Wing Lian <wing.lian@gmail.com>
Co-authored-by: Woosuk Kwon <woosuk.kwon@berkeley.edu>

vllm/config.py

@@ -351,6 +351,17 @@ def _get_and_verify_max_len(
         if max_len_key is not None:
             derived_max_model_len = min(derived_max_model_len, max_len_key)
 
+    rope_scaling = getattr(hf_config, "rope_scaling", None)
+    if rope_scaling is not None:
+        if derived_max_model_len == float("inf"):
+            raise ValueError(
+                "When using rope_scaling, the model's config.json must "
+                "contain one of the following keys to determine the original "
+                f"maximum length of the model: {possible_keys}")
+        assert "factor" in rope_scaling
+        scaling_factor = rope_scaling["factor"]
+        derived_max_model_len *= scaling_factor
+
     if max_model_len is None:
         max_model_len = derived_max_model_len
     elif max_model_len > derived_max_model_len:

vllm/model_executor/layers/attention.py

 """Multi-head attention."""
-from typing import List, Optional
+from typing import Any, Dict, List, Optional
 
 import torch
 import torch.nn as nn
@@ -9,8 +9,10 @@ from xformers.ops.fmha.attn_bias import (BlockDiagonalCausalMask,
 
 from vllm import attention_ops
 from vllm import cache_ops
-from vllm import pos_encoding_ops
 from vllm.model_executor.input_metadata import InputMetadata
+from vllm.model_executor.layers.rotary_embedding import (
+    DynamicNTKScalingRotaryEmbedding, LinearScalingRotaryEmbedding,
+    RotaryEmbedding)
 
 _SUPPORTED_HEAD_SIZES = [64, 80, 96, 112, 128, 256]
 
@@ -247,7 +249,7 @@ class PagedAttention(nn.Module):
 
 
 class PagedAttentionWithRoPE(PagedAttention):
-    """PagedAttention with rotary embedding."""
+    """PagedAttention with rotary positional embedding."""
 
     def __init__(
         self,
@@ -259,34 +261,26 @@ class PagedAttentionWithRoPE(PagedAttention):
         base: int = 10000,
         num_kv_heads: Optional[int] = None,
         is_neox_style: bool = True,
+        rope_scaling: Optional[Dict[str, Any]] = None,
     ) -> None:
         super().__init__(num_heads, head_size, scale, num_kv_heads)
-        self.is_neox_style = is_neox_style
-
-        # Create the cos and sin cache.
-        # NOTE(woosuk): The HF implementation uses `torch.arange(...).float()`.
-        # However, we use `torch.arange(..., dtype=torch.float)` instead to
-        # avoid numerical issues with large base values (e.g., 10000000).
-        # This may cause a slight numerical difference between the HF
-        # implementation and ours.
-        # NOTE(woosuk): To exactly match the HF implementation, we need to
-        # use CPU to compute the cache and then move it to GPU. However, we
-        # create the cache on GPU for faster initialization. This may cause
-        # a slight numerical difference between the HF implementation and ours.
-        inv_freq = 1.0 / (base**(torch.arange(
-            0, rotary_dim, 2, dtype=torch.float, device="cuda") / rotary_dim))
-        t = torch.arange(max_position, dtype=torch.float, device="cuda")
-        freqs = torch.einsum("i,j -> ij", t, inv_freq)
-        cos = freqs.cos()
-        sin = freqs.sin()
-        cache = torch.cat((cos, sin), dim=-1)
-
-        # FIXME(woosuk): This assumes that we configure the default dtype when
-        # initializing the model.
-        torch_dtype = torch.get_default_dtype()
-        cache = cache.to(torch_dtype)
-        # Embedding size: [max_position, rotary_dim]
-        self.register_buffer("cos_sin_cache", cache, persistent=False)
+        if rope_scaling is None:
+            self.rotary_emb = RotaryEmbedding(head_size, rotary_dim,
+                                              max_position, base,
+                                              is_neox_style)
+        else:
+            scaling_type = rope_scaling["type"]
+            scaling_factor = rope_scaling["factor"]
+            if scaling_type == "linear":
+                self.rotary_emb = LinearScalingRotaryEmbedding(
+                    head_size, rotary_dim, max_position, base, is_neox_style,
+                    scaling_factor)
+            elif scaling_type == "dynamic":
+                self.rotary_emb = DynamicNTKScalingRotaryEmbedding(
+                    head_size, rotary_dim, max_position, base, is_neox_style,
+                    scaling_factor)
+            else:
+                raise ValueError(f"Unknown RoPE scaling type {scaling_type}")
 
     def forward(
         self,
@@ -319,14 +313,7 @@ class PagedAttentionWithRoPE(PagedAttention):
 
         # Apply rotary embedding to the query and key before passing them
         # to the attention op.
-        pos_encoding_ops.rotary_embedding(
-            positions,
-            query,
-            key,
-            self.head_size,
-            self.cos_sin_cache,
-            self.is_neox_style,
-        )
+        query, key = self.rotary_emb(positions, query, key)
         return super().forward(
             query,
             key,

vllm/model_executor/layers/rotary_embedding.py

+# coding=utf-8
+# Adapted from
+# https://github.com/huggingface/transformers/blob/v4.33.2/src/transformers/models/llama/modeling_llama.py
+# Copyright 2023 The vLLM team.
+# Copyright 2022 EleutherAI and the HuggingFace Inc. team. All rights reserved.
+#
+# This code is based on EleutherAI's GPT-NeoX library and the GPT-NeoX
+# and OPT implementations in this library. It has been modified from its
+# original forms to accommodate minor architectural differences compared
+# to GPT-NeoX and OPT used by the Meta AI team that trained the model.
+#
+# 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.
+"""Rotary Positional Embeddings."""
+from typing import Tuple, Union
+
+import torch
+import torch.nn as nn
+
+from vllm import pos_encoding_ops
+
+
+class RotaryEmbedding(nn.Module):
+    """Original rotary positional embedding."""
+
+    def __init__(
+        self,
+        head_size: int,
+        rotary_dim: int,
+        max_position_embeddings: int,
+        base: int,
+        is_neox_style: bool,
+    ) -> None:
+        super().__init__()
+        self.head_size = head_size
+        self.rotary_dim = rotary_dim
+        self.max_position_embeddings = max_position_embeddings
+        self.base = base
+        self.is_neox_style = is_neox_style
+
+        cache = self._compute_cos_sin_cache()
+        cache = cache.to(torch.get_default_dtype())
+        self.register_buffer("cos_sin_cache", cache, persistent=False)
+
+    def _compute_inv_freq(self, base: Union[int, float]) -> torch.Tensor:
+        """Compute the inverse frequency."""
+        # NOTE(woosuk): The HF implementation uses `torch.arange(...).float()`.
+        # However, we use `torch.arange(..., dtype=torch.float)` instead to
+        # avoid numerical issues with large base values (e.g., 10000000).
+        # This may cause a slight numerical difference between the HF
+        # implementation and ours.
+        # NOTE(woosuk): To exactly match the HF implementation, we need to
+        # use CPU to compute the cache and then move it to GPU. However, we
+        # create the cache on GPU for faster initialization. This may cause
+        # a slight numerical difference between the HF implementation and ours.
+        inv_freq = 1.0 / (base**(torch.arange(
+            0, self.rotary_dim, 2, dtype=torch.float, device="cuda") /
+                                 self.rotary_dim))
+        return inv_freq
+
+    def _compute_cos_sin_cache(self) -> torch.Tensor:
+        """Compute the cos and sin cache."""
+        inv_freq = self._compute_inv_freq(self.base)
+        t = torch.arange(self.max_position_embeddings,
+                         dtype=torch.float,
+                         device="cuda")
+
+        freqs = torch.einsum("i,j -> ij", t, inv_freq)
+        cos = freqs.cos()
+        sin = freqs.sin()
+        cache = torch.cat((cos, sin), dim=-1)
+        return cache
+
+    def forward(
+        self,
+        positions: torch.Tensor,
+        query: torch.Tensor,
+        key: torch.Tensor,
+    ) -> Tuple[torch.Tensor, torch.Tensor]:
+        # pos_encoding_ops.rotary_embedding() is an in-place operation that
+        # updates the query and key tensors.
+        pos_encoding_ops.rotary_embedding(positions, query, key,
+                                          self.head_size, self.cos_sin_cache,
+                                          self.is_neox_style)
+        return query, key
+
+
+class LinearScalingRotaryEmbedding(RotaryEmbedding):
+    """RotaryEmbedding extended with linear scaling.
+
+    Credits to the Reddit user /u/kaiokendev
+    """
+
+    def __init__(
+        self,
+        head_size: int,
+        rotary_dim: int,
+        max_position_embeddings: int,
+        base: int,
+        is_neox_style: bool,
+        scaling_factor: float,
+    ) -> None:
+        self.scaling_factor = scaling_factor
+        super().__init__(head_size, rotary_dim, max_position_embeddings, base,
+                         is_neox_style)
+
+    def _compute_cos_sin_cache(self) -> torch.Tensor:
+        inv_freq = self._compute_inv_freq(self.base)
+        # NOTE(woosuk): self.max_position_embeddings is the original
+        # maximum length before applying the rope scaling.
+        # Thus, the maximum length after applying the rope scaling is
+        # self.max_position_embeddings * self.scaling_factor.
+        max_len = self.max_position_embeddings * self.scaling_factor
+        t = torch.arange(max_len, dtype=torch.float, device="cuda")
+        t = t / self.scaling_factor
+
+        freqs = torch.einsum("i,j -> ij", t, inv_freq)
+        cos = freqs.cos()
+        sin = freqs.sin()
+        cache = torch.cat((cos, sin), dim=-1)
+        return cache
+
+
+class DynamicNTKScalingRotaryEmbedding(RotaryEmbedding):
+    """RotaryEmbedding extended with Dynamic NTK scaling.
+
+    Credits to the Reddit users /u/bloc97 and /u/emozilla
+    """
+
+    def __init__(
+        self,
+        head_size: int,
+        rotary_dim: int,
+        max_position_embeddings: int,
+        base: int,
+        is_neox_style: bool,
+        scaling_factor: float,
+    ) -> None:
+        self.scaling_factor = scaling_factor
+        super().__init__(head_size, rotary_dim, max_position_embeddings, base,
+                         is_neox_style)
+
+    def _compute_cos_sin_cache(self) -> torch.Tensor:
+        # NOTE(woosuk): self.max_position_embeddings is the original
+        # maximum length before applying the rope scaling.
+        # Thus, the maximum length after applying the rope scaling is
+        # self.max_position_embeddings * self.scaling_factor.
+        max_len = self.max_position_embeddings * self.scaling_factor
+        base = self.base * (
+            (self.scaling_factor * max_len / self.max_position_embeddings) -
+            (self.scaling_factor - 1))**(self.rotary_dim /
+                                         (self.rotary_dim - 2))
+        inv_freq = self._compute_inv_freq(base)
+        t = torch.arange(max_len, dtype=torch.float, device="cuda")
+
+        freqs = torch.einsum("i,j -> ij", t, inv_freq)
+        cos = freqs.cos()
+        sin = freqs.sin()
+        cache = torch.cat((cos, sin), dim=-1)
+        return cache

vllm/model_executor/models/llama.py

@@ -25,7 +25,7 @@
 The input of the model is flattened to a 1D tensor of tokens. The model uses
 InputMetadata to extract the original 2D shape of the input.
 """
-from typing import List, Optional, Tuple
+from typing import Any, Dict, List, Optional, Tuple
 
 import torch
 from torch import nn
@@ -92,6 +92,7 @@ class LlamaAttention(nn.Module):
         num_heads: int,
         num_kv_heads: int,
         rope_theta: float = 10000,
+        rope_scaling: Optional[Dict[str, Any]] = None,
         max_position_embeddings: int = 8192,
         quant_config: Optional[QuantizationConfig] = None,
     ) -> None:
@@ -135,7 +136,8 @@ class LlamaAttention(nn.Module):
             base=self.rope_theta,
             max_position=self.max_position_embeddings,
             rotary_dim=self.head_dim,
-            num_kv_heads=self.num_kv_heads)
+            num_kv_heads=self.num_kv_heads,
+            rope_scaling=rope_scaling)
 
     def forward(
         self,
@@ -165,6 +167,7 @@ class LlamaDecoderLayer(nn.Module):
         self.hidden_size = config.hidden_size
         # Requires transformers > 4.32.0
         rope_theta = getattr(config, "rope_theta", 10000)
+        rope_scaling = getattr(config, "rope_scaling", None)
         max_position_embeddings = getattr(config, "max_position_embeddings",
                                           8192)
         self.self_attn = LlamaAttention(
@@ -172,6 +175,7 @@ class LlamaDecoderLayer(nn.Module):
             num_heads=config.num_attention_heads,
             num_kv_heads=config.num_key_value_heads,
             rope_theta=rope_theta,
+            rope_scaling=rope_scaling,
             max_position_embeddings=max_position_embeddings,
             quant_config=quant_config,
         )