摘要
上下文工程正在快速演进,本文展望Automatic Context Management、Context Routing、Hierarchical Context、Memory-augmented LM、State Space Models(如Mamba、RWKV)等前沿技术,分析LLM上下文处理的未来发展方向。
关键词速览
| 术语 | 英文 | 说明 |
|---|---|---|
| ACM | Automatic Context Management | 自动上下文管理 |
| Context Routing | Context Routing | 上下文路由 |
| Hierarchical Context | Hierarchical Context | 分层上下文 |
| Memory LM | Memory-Augmented LM | 记忆增强语言模型 |
| SSM | State Space Models | 状态空间模型 |
| Mamba | Mamba | 选择性状态空间模型 |
| RWKV | RWKV | 循环GPT |
| Linear Attention | Linear Attention | 线性注意力 |
| Mixture of Experts | Mixture of Experts | 专家混合 |
| Long Range Arena | Long Range Arena | 长程竞技场 |
一、Automatic Context Management
1.1 ACM概述
自动上下文管理(ACM)是让LLM自动决定如何处理上下文的范式:
传统方式:
用户 ──► 手动设计prompt ──► LLM ──► 固定上下文
ACM方式:
用户 ──► ACM系统自动决策 ──► LLM
│
├── 决定包含什么
├── 决定如何组织
├── 决定压缩程度
└── 决定存储位置
1.2 ACM核心组件
class AutomaticContextManager:
"""自动上下文管理器"""
def __init__(
self,
llm_client,
memory_store,
embedding_model
):
self.llm = llm_client
self.memory = memory_store
self.embedding = embedding_model
def manage_context(
self,
user_input: str,
session_id: str
) -> dict:
"""
自动管理上下文
"""
# 1. 分析任务类型
task_analysis = self._analyze_task(user_input)
# 2. 决定上下文策略
strategy = self._decide_strategy(task_analysis)
# 3. 收集相关上下文
contexts = self._collect_contexts(user_input, strategy)
# 4. 决定是否压缩
if self._needs_compression(contexts, strategy):
contexts = self._compress_contexts(contexts, strategy)
# 5. 决定是否存储
if strategy.get('should_remember'):
self._store_in_memory(user_input, contexts, session_id)
return {
'contexts': contexts,
'strategy': strategy,
'task_type': task_analysis['type'],
'compression_applied': self._needs_compression(contexts, strategy)
}
def _analyze_task(self, user_input: str) -> dict:
"""分析任务类型"""
prompt = f"""分析以下用户输入,确定其任务类型和上下文需求。
输入:{user_input}
分析维度:
1. 任务类型:factual(事实查询)/creative(创意)/reasoning(推理)/conversation(对话)
2. 上下文依赖度:高/中/低
3. 需要的历史深度:短期/中期/长期
4. 是否需要专业知识
输出JSON格式:"""
result = self.llm.generate(prompt)
# 解析JSON
return json.loads(result)
def _decide_strategy(self, task_analysis: dict) -> dict:
"""决定处理策略"""
strategies = {
'factual': {
'context_window': 'focused', # 聚焦在相关事实上
'compression': 'aggressive',
'should_remember': True,
'retrieval_weight': 0.8
},
'creative': {
'context_window': 'broad', # 更宽泛的上下文
'compression': 'light',
'should_remember': False,
'retrieval_weight': 0.3
},
'reasoning': {
'context_window': 'complete', # 完整上下文
'compression': 'minimal',
'should_remember': True,
'retrieval_weight': 0.5
},
'conversation': {
'context_window': 'recent', # 最近对话
'compression': 'moderate',
'should_remember': True,
'retrieval_weight': 0.2
}
}
task_type = task_analysis.get('type', 'conversation')
return strategies.get(task_type, strategies['conversation'])1.3 自适应压缩
class AdaptiveCompressor:
"""自适应压缩器"""
def __init__(self, llm_client):
self.llm = llm_client
self.compression_models = {
'light': LightCompressor(),
'moderate': ModerateCompressor(),
'aggressive': AggressiveCompressor()
}
def compress_adaptive(
self,
contexts: List[str],
task_type: str,
available_tokens: int
) -> List[str]:
"""根据任务自适应压缩"""
# 选择压缩级别
if task_type == 'factual':
compression_level = 'aggressive'
elif task_type == 'reasoning':
compression_level = 'light'
else:
compression_level = 'moderate'
compressor = self.compression_models[compression_level]
# 压缩每个上下文
compressed = []
for ctx in contexts:
ctx_tokens = self._estimate_tokens(ctx)
if ctx_tokens <= available_tokens:
compressed.append(ctx)
else:
target_ratio = available_tokens / ctx_tokens
compressed.append(compressor.compress(ctx, target_ratio))
return compressed二、Context Routing
2.1 Context Routing概念
Context Routing根据内容类型将信息路由到不同的处理路径:
class ContextRouter:
"""上下文路由器"""
def __init__(self):
self.routing_rules = {
'factual': {
'path': 'retrieval', # 知识库检索
'compression': 'high',
'storage': 'knowledge_base'
},
'personal': {
'path': 'memory', # 个人记忆
'compression': 'low',
'storage': 'user_profile'
},
'session': {
'path': 'window', # 短期窗口
'compression': 'minimal',
'storage': 'session_cache'
},
'system': {
'path': 'instruction', # 指令处理
'compression': 'none',
'storage': 'system_prompt'
}
}
def route(self, content: str, content_type: str = None) -> dict:
"""路由内容"""
# 自动检测内容类型
if content_type is None:
content_type = self._detect_content_type(content)
routing = self.routing_rules.get(
content_type,
self.routing_rules['session']
)
return {
'content': content,
'type': content_type,
'path': routing['path'],
'compression': routing['compression'],
'storage': routing['storage']
}
def _detect_content_type(self, content: str) -> str:
"""检测内容类型"""
# 简化实现
if any(kw in content for kw in ['记住', '我的名字', '偏好']):
return 'personal'
elif any(kw in content for kw in ['什么是', '定义', '如何']):
return 'factual'
elif '系统' in content or '你是一个' in content:
return 'system'
else:
return 'session'2.2 动态上下文选择
class DynamicContextSelector:
"""动态上下文选择器"""
def __init__(
self,
embedding_model,
attention_scorer
):
self.embedding = embedding_model
self.attention_scorer = attention_scorer
def select(
self,
query: str,
candidates: List[Dict],
budget_tokens: int,
strategy: str = "weighted"
) -> List[Dict]:
"""
动态选择上下文
strategy: 'greedy', 'weighted', 'diverse'
"""
if strategy == "greedy":
return self._greedy_select(query, candidates, budget_tokens)
elif strategy == "weighted":
return self._weighted_select(query, candidates, budget_tokens)
else:
return self._diverse_select(query, candidates, budget_tokens)
def _greedy_select(
self,
query: str,
candidates: List[Dict],
budget_tokens: int
) -> List[Dict]:
"""贪心选择"""
query_emb = self.embedding.encode(query)
# 按相关性排序
scored = []
for c in candidates:
c_emb = self.embedding.encode(c['content'])
score = self._cosine_similarity(query_emb, c_emb)
scored.append((score, c))
scored.sort(key=lambda x: x[0], reverse=True)
# 贪心选择
selected = []
current_tokens = 0
for score, c in scored:
c_tokens = c.get('token_count', self._estimate_tokens(c['content']))
if current_tokens + c_tokens <= budget_tokens:
selected.append(c)
current_tokens += c_tokens
return selected
def _weighted_select(
self,
query: str,
candidates: List[Dict],
budget_tokens: int
) -> List[Dict]:
"""加权选择:考虑相关性和重要性"""
query_emb = self.embedding.encode(query)
scored = []
for c in candidates:
relevance = self._cosine_similarity(
query_emb,
self.embedding.encode(c['content'])
)
importance = c.get('importance', 0.5)
# 综合分数
combined_score = 0.7 * relevance + 0.3 * importance
scored.append((combined_score, c))
scored.sort(key=lambda x: x[0], reverse=True)
selected = []
current_tokens = 0
for score, c in scored:
c_tokens = c.get('token_count', self._estimate_tokens(c['content']))
if current_tokens + c_tokens <= budget_tokens:
selected.append(c)
current_tokens += c_tokens
return selected
def _diverse_select(
self,
query: str,
candidates: List[Dict],
budget_tokens: int
) -> List[Dict]:
"""多样性选择"""
# 先按相关性筛选top-k
query_emb = self.embedding.encode(query)
scored = []
for c in candidates:
relevance = self._cosine_similarity(
query_emb,
self.embedding.encode(c['content'])
)
scored.append((relevance, c))
scored.sort(key=lambda x: x[0], reverse=True)
top_k = scored[:min(20, len(scored))]
# MMSR多样性选择
selected = []
current_tokens = 0
for relevance, c in top_k:
c_tokens = c.get('token_count', self._estimate_tokens(c['content']))
if current_tokens + c_tokens > budget_tokens:
continue
# 检查与已选内容的多样性
is_diverse = True
for s in selected:
sim = self._cosine_similarity(
self.embedding.encode(c['content']),
self.embedding.encode(s['content'])
)
if sim > 0.9: # 太相似
is_diverse = False
break
if is_diverse or len(selected) < 3: # 至少选3个
selected.append(c)
current_tokens += c_tokens
return selected
@staticmethod
def _cosine_similarity(a, b):
dot = sum(x * y for x, y in zip(a, b))
norm_a = sum(x * x for x in a) ** 0.5
norm_b = sum(x * x for x in b) ** 0.5
return dot / (norm_a * norm_b + 1e-8)
@staticmethod
def _estimate_tokens(text: str) -> int:
chinese = sum(1 for c in text if '\u4e00' <= c <= '\u9fff')
english = len(text.split()) - chinese
return int(chinese * 0.5 + english * 0.25)三、Hierarchical Context
3.1 分层上下文架构
┌─────────────────────────────────────────────────────────────────┐
│ 分层上下文架构 │
├─────────────────────────────────────────────────────────────────┤
│ │
│ L3: 全局层 (Global) │
│ - 跨会话的知识 │
│ - 用户长期偏好 │
│ - 领域知识库 │
│ │
│ L2: 会话层 (Session) │
│ - 当前会话的历史 │
│ - 任务上下文 │
│ - 临时信息 │
│ │
│ L1: 实时层 (Real-time) │
│ - 当前输入 │
│ - 活跃焦点 │
│ - 立即上下文 │
│ │
└─────────────────────────────────────────────────────────────────┘
3.2 实现代码
class HierarchicalContextManager:
"""分层上下文管理器"""
def __init__(self):
self.global_layer = GlobalContextStore()
self.session_layer = SessionContextStore()
self.realtime_layer = {}
def get_context(
self,
query: str,
session_id: str,
config: dict = None
) -> str:
"""获取分层上下文"""
if config is None:
config = self._get_default_config()
context_parts = []
# 1. 实时层
if config.get('include_realtime', True):
realtime = self.realtime_layer.get(session_id, [])
context_parts.extend(realtime)
# 2. 会话层
if config.get('include_session', True):
session_context = self.session_layer.get(session_id)
if session_context:
context_parts.append(f"[会话上下文]\n{session_context}")
# 3. 全局层
if config.get('include_global', True):
global_context = self.global_layer.get_relevant(query)
if global_context:
context_parts.append(f"[全局知识]\n{global_context}")
return "\n\n".join(context_parts)
def update_context(
self,
session_id: str,
content: str,
layer: str = 'session'
):
"""更新指定层"""
if layer == 'session':
self.session_layer.add(session_id, content)
elif layer == 'global':
self.global_layer.add(content)
elif layer == 'realtime':
if session_id not in self.realtime_layer:
self.realtime_layer[session_id] = []
self.realtime_layer[session_id].append(content)
def _get_default_config(self) -> dict:
"""获取默认配置"""
return {
'include_realtime': True,
'include_session': True,
'include_global': True,
'max_tokens': {
'realtime': 2000,
'session': 8000,
'global': 5000
}
}四、Memory-Augmented LM
4.1 记忆增强语言模型
class MemoryAugmentedLM:
"""记忆增强语言模型"""
def __init__(
self,
llm_client,
memory_store,
controller
):
self.llm = llm_client
self.memory = memory_store
self.controller = controller # 记忆控制器
def generate_with_memory(
self,
query: str,
session_id: str
) -> str:
"""带记忆的生成"""
# 1. 从记忆中检索相关内容
relevant_memories = self.memory.retrieve(query, session_id)
# 2. 决定读取哪些记忆
selected_memories = self.controller.select_read(
query,
relevant_memories
)
# 3. 构建提示
prompt = self._build_prompt(query, selected_memories)
# 4. 生成
response = self.llm.generate(prompt)
# 5. 决定是否写入记忆
if self.controller.should_write(response, session_id):
self.memory.write(response, session_id)
return response
def learn_from_feedback(
self,
query: str,
response: str,
feedback: dict,
session_id: str
):
"""从反馈中学习"""
# 更新记忆权重
self.memory.update_weights(
query,
response,
feedback,
session_id
)
# 如果反馈负面,修正相关记忆
if feedback.get('rating', 0) < 3:
self._revise_memory(query, response, feedback, session_id)4.2 神经记忆模块
class NeuralMemoryModule:
"""神经记忆模块"""
def __init__(self, embedding_dim: int = 768):
self.embedding_dim = embedding_dim
self.memory_keys = [] # 记忆的key向量
self.memory_values = [] # 记忆的内容
self.memory_strengths = [] # 记忆强度
def write(
self,
key: str,
value: str,
strength: float = 1.0
):
"""写入记忆"""
# 简化:直接存储
self.memory_keys.append(key)
self.memory_values.append(value)
self.memory_strengths.append(strength)
def read(self, query: str, top_k: int = 5) -> List[dict]:
"""读取记忆"""
# 简化实现
# 实际中应该用向量相似度
results = []
for i, key in enumerate(self.memory_keys):
# 简单的关键词匹配
overlap = len(set(key.split()) & set(query.split()))
if overlap > 0:
results.append({
'content': self.memory_values[i],
'strength': self.memory_strengths[i],
'relevance': overlap / len(key.split())
})
# 排序并返回top_k
results.sort(key=lambda x: x['strength'] * x['relevance'], reverse=True)
return results[:top_k]
def update_strength(
self,
index: int,
delta: float
):
"""更新记忆强度"""
if 0 <= index < len(self.memory_strengths):
self.memory_strengths[index] += delta
# 限制范围
self.memory_strengths[index] = max(0.1, min(2.0, self.memory_strengths[index]))五、State Space Models
5.1 SSM基础
状态空间模型(SSM)是一种新型的序列建模架构,与Transformer相比具有线性复杂度的优势:
class StateSpaceModel:
"""
状态空间模型基础
SSM通过状态方程建模序列:
x(t+1) = Ax(t) + Bu(t)
y(t) = Cx(t) + Du(t)
其中:
- A: 状态转移矩阵
- B: 输入矩阵
- C: 输出矩阵
- D: 直连矩阵
"""
def __init__(
self,
state_dim: int,
input_dim: int,
output_dim: int
):
self.state_dim = state_dim
self.input_dim = input_dim
self.output_dim = output_dim
# 初始化参数
self.A = np.random.randn(state_dim, state_dim) * 0.1
self.B = np.random.randn(state_dim, input_dim) * 0.1
self.C = np.random.randn(output_dim, state_dim) * 0.1
self.D = np.zeros((output_dim, input_dim))
def forward(self, u: np.ndarray) -> tuple:
"""
SSM前向传播
Args:
u: 输入序列 [seq_len, input_dim]
Returns:
y: 输出序列 [seq_len, output_dim]
state: 最终状态 [state_dim]
"""
seq_len = len(u)
state = np.zeros(self.state_dim)
outputs = []
for t in range(seq_len):
# 状态更新
state = self.A @ state + self.B @ u[t]
# 输出
y = self.C @ state + self.D @ u[t]
outputs.append(y)
return np.array(outputs), state5.2 Mamba架构
Mamba是选择性状态空间模型(Selective SSM),通过输入依赖的选择机制实现:
class MambaBlock:
"""
Mamba选择机制
核心改进:让A, B, C矩阵成为输入的函数,
从而实现内容感知的序列建模
"""
def __init__(
self,
d_model: int,
d_state: int = 16,
d_conv: int = 4,
expand: int = 2
):
self.d_model = d_model
self.d_state = d_state
self.d_conv = d_conv
self.expand = expand
d_inner = d_model * expand
# 投影矩阵
self.in_proj = nn.Linear(d_model, d_inner * 2)
# 卷积
self.conv = nn.Conv1d(
d_inner,
d_inner,
d_conv,
padding=d_conv - 1
)
# SSM参数投影
self.x_proj = nn.Linear(d_inner, d_state * 2 + 1)
self.dt_proj = nn.Linear(d_state, d_inner)
# 输出投影
self.out_proj = nn.Linear(d_inner, d_model)
# A矩阵初始化
self.A_log = nn.Parameter(torch.randn(d_state, d_model))
def forward(self, x: torch.Tensor) -> torch.Tensor:
"""
Mamba前向传播
"""
batch, seq_len, d = x.shape
# 输入投影
xz = self.in_proj(x)
x_inner, z = xz.chunk(2, dim=-1)
# 卷积
x_conv = self.conv(x_inner.transpose(1, 2)).transpose(1, 2)
x_conv = F.silu(x_conv)
# SSM参数(选择机制)
x_dbl = self.x_proj(x_conv)
dt, B, C = x_dbl.split([self.d_state, self.d_state, self.d_state], dim=-1)
dt = self.dt_proj(dt)
# 选择性扫描
y = self.selective_scan(
x_conv,
dt,
self.A_log,
B,
C,
z
)
# 输出
y = y * F.silu(z)
return self.out_proj(y)
def selective_scan(
self,
u,
dt,
A,
B,
C,
z
):
"""
选择性扫描算法
这是Mamba的核心:参数由输入决定
"""
# 简化实现
# 实际使用硬件感知的并行扫描
batch, seq_len, d_inner = u.shape
d_state = self.d_state
# 离散化
A_dis = torch.exp(torch.einsum('bd,dn->bdn', dt, A))
B_dis = torch.einsum('bdn,bd->bdn', B, dt)
# 扫描
y = torch.zeros_like(u)
h = torch.zeros(batch, d_state, device=u.device)
for i in range(seq_len):
h = A_dis[:, i] * h + B_dis[:, i] * u[:, i:i+1]
y[:, i] = torch.einsum('bn,bn->b', h, C[:, i])
return y5.3 RWKV架构
RWKV(Receptance Weighted Key Value)是一种结合RNN和Transformer优点的架构:
class RWKVBlock:
"""
RWKV块
特点:
- 线性注意力(O(n)复杂度)
- 可以并行训练
- 可以高效推理
- 保留长期依赖
"""
def __init__(
self,
d_model: int,
d_ffn: int,
layer_id: int,
n_layers: int
):
self.layer_id = layer_id
self.n_layers = n_layers
# 时间混合
self.time_mix = TimeMixing(d_model)
# 通道混合
self.channel_mix = ChannelMixing(d_model, d_ffn)
def forward(self, x: torch.Tensor, last_state=None) -> tuple:
"""RWKV前向传播"""
# 时间混合(类似注意力)
x, new_time_state = self.time_mix(x, last_state)
# 通道混合(类似FFN)
x = self.channel_mix(x)
return x, {'time': new_time_state}
class TimeMixing(nn.Module):
"""RWKV时间混合"""
def __init__(self, d_model: int):
super().__init__()
self.d_model = d_model
# RWKV参数
self.time_decay = nn.Parameter(torch.zeros(d_model))
self.time_first = nn.Parameter(torch.zeros(d_model))
# 投影
self.key = nn.Linear(d_model, d_model)
self.value = nn.Linear(d_model, d_model)
self.receptance = nn.Linear(d_model, d_model)
self.output = nn.Linear(d_model, d_model)
def forward(self, x: torch.Tensor, state=None) -> tuple:
"""
RWKV时间混合
核心公式:
wkv = sum_i(exp(-(i-t+1)*decay) * value_i) / sum_i(exp(-(i-t+1)*decay))
rwkv = sigmoid(receptance) * wkv
然后 output = rwkv @ output_weights
"""
B, T, C = x.shape
# 投影
k = self.key(x)
v = self.value(x)
r = torch.sigmoid(self.receptance(x))
# WKV计算(简化)
wkv = self._compute_wkv(k, v)
# 输出
rwkv = r * wkv
output = self.output(rwkv)
return output, None # state简化
def _compute_wkv(self, k, v):
"""计算RWKV的wkv项"""
# 简化实现
# 实际使用数值稳定的并行算法
B, T, C = k.shape
wkv = torch.zeros_like(k)
for t in range(T):
w = torch.exp(self.time_decay)
w_first = torch.exp(self.time_first)
# 计算分母
denom = w_first
# 计算分子
numer = w_first * v[:, t:t+1]
for i in range(t):
denom = 1 + w * denom
numer = w * numer + w * v[:, i:i+1]
wkv[:, t] = numer / denom
return wkv5.4 SSM vs Transformer对比
| 特性 | Transformer | SSM (Mamba/RWKV) |
|---|---|---|
| 时间复杂度 | O(n²) | O(n) |
| 空间复杂度 | O(n²) | O(n) |
| 长期依赖 | 有限(位置编码) | 自然保持 |
| 并行训练 | 完全并行 | 几乎完全并行 |
| 推理速度 | 慢(完整注意力) | 快(线性) |
| 可解释性 | 注意力权重 | 状态向量 |
| 上下文学习 | 强 | 较弱(但增强中) |
| 硬件效率 | 中等 | 高 |
六、未来展望
6.1 短期发展趋势(1-2年)
- 上下文窗口继续扩大:百万token将成为常态
- 更智能的压缩:基于语义的理解而非规则
- 原生缓存支持:硬件和模型层面的缓存
- 多模态上下文:文本、图像、视频的统一处理
6.2 中期发展趋势(3-5年)
- 自适应上下文:模型自动学习最优上下文策略
- 外部记忆整合:持久的、可学习的外部记忆系统
- State Space融合:SSM与Transformer的深度融合
- 个性化上下文:针对用户定制的上下文管理
6.3 长期愿景
┌─────────────────────────────────────────────────────────────────┐
│ 理想上下文系统 │
├─────────────────────────────────────────────────────────────────┤
│ │
│ 用户意图 ──► 智能理解 ──► 最优上下文 ──► 高效推理 │
│ │ │
│ ┌─────────┴─────────┐ │
│ │ │ │
│ 长期记忆 短期窗口 │
│ │ │ │
│ ┌─────┴─────┐ ┌───┴───┐ │
│ │ │ │ │ │
│ 知识图谱 个人记忆 会话历史 实时信息 │
│ │
│ 特点:上下文像人脑一样自然、高效、个性化 │
│ │
└─────────────────────────────────────────────────────────────────┘
七、相关主题
八、参考文献
- Gu, A., et al. (2021). Efficiently Modeling Long Sequences with Structured State Spaces. NeurIPS.
- Dao, T., et al. (2023). Hungry Hungry Hippos: Towards Language Modeling with State Space Models. ICLR.
- Peng, B., et al. (2023). RWKV: Reinventing RNNs for the Transformer Era. ACL.
- Liu, H., et al. (2024). Mixture-of-Experts Meets Instruction Tuning. arXiv.
- Anthropic (2024). Claude 3.5 System Card.