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sglang/python/sglang/srt/models/lfm2_moe.py
2026-02-12 01:03:43 +08:00

680 lines
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Python

"""
LFM2-MoE (Liquid Foundation Model 2 - Mixture of Experts) implementation for SGLang.
This is a hybrid architecture with attention, ShortConv, and MoE layers:
- Attention layers use standard KV cache (RadixAttention)
- Conv layers use MambaPool for state caching (via HybridReqToTokenPool)
- First `num_dense_layers` use dense MLP, rest use MoE with sigmoid routing
Key MoE characteristics:
- Sigmoid routing (not softmax) - auxiliary-loss-free style
- Expert bias (fp32) affects selection but not weighting
- Post-hoc normalization of top-k weights
"""
from typing import Iterable, Optional, Set, Tuple
import torch
from torch import nn
from sglang.srt.configs.lfm2_moe import Lfm2MoeConfig
from sglang.srt.distributed import get_pp_group, get_tensor_model_parallel_world_size
from sglang.srt.layers.activation import SiluAndMul
from sglang.srt.layers.attention.mamba.causal_conv1d import (
causal_conv1d_fn,
causal_conv1d_update,
)
from sglang.srt.layers.layernorm import RMSNorm
from sglang.srt.layers.linear import (
MergedColumnParallelLinear,
QKVParallelLinear,
ReplicatedLinear,
RowParallelLinear,
)
from sglang.srt.layers.logits_processor import LogitsProcessor
from sglang.srt.layers.moe.fused_moe_triton import FusedMoE
from sglang.srt.layers.moe.topk import TopK
from sglang.srt.layers.quantization.base_config import QuantizationConfig
from sglang.srt.layers.radix_attention import RadixAttention
from sglang.srt.layers.rotary_embedding import get_rope
from sglang.srt.layers.vocab_parallel_embedding import (
ParallelLMHead,
VocabParallelEmbedding,
)
from sglang.srt.model_executor.forward_batch_info import ForwardBatch
from sglang.srt.model_loader.weight_utils import (
default_weight_loader,
sharded_weight_loader,
)
from sglang.srt.utils import add_prefix, make_layers, set_weight_attrs
class Lfm2MoeMLP(nn.Module):
"""Dense MLP for first N layers (before MoE kicks in)."""
def __init__(
self,
config: Lfm2MoeConfig,
quant_config: Optional[QuantizationConfig] = None,
prefix: str = "",
):
super().__init__()
# Use MergedColumnParallelLinear for w1/w3 (gate/up projections)
self.gate_up_proj = MergedColumnParallelLinear(
config.hidden_size,
[config.intermediate_size] * 2,
bias=False,
quant_config=quant_config,
prefix=add_prefix("gate_up_proj", prefix),
)
self.down_proj = RowParallelLinear(
config.intermediate_size,
config.hidden_size,
bias=False,
quant_config=quant_config,
prefix=add_prefix("down_proj", prefix),
)
self.act_fn = SiluAndMul()
def forward(self, x: torch.Tensor) -> torch.Tensor:
gate_up, _ = self.gate_up_proj(x)
x = self.act_fn(gate_up)
out, _ = self.down_proj(x)
return out
class Lfm2MoeSparseMoeBlock(nn.Module):
"""
Sparse MoE block with sigmoid routing using optimized FusedMoE.
Key features:
- Sigmoid scoring (not softmax) - auxiliary-loss-free style
- Expert bias (fp32) for load balancing
- Bias affects selection only, not weighting
- Uses FusedMoE for efficient batched expert computation
"""
def __init__(
self,
config: Lfm2MoeConfig,
layer_idx: int,
quant_config: Optional[QuantizationConfig] = None,
prefix: str = "",
):
super().__init__()
self.tp_size = get_tensor_model_parallel_world_size()
self.routed_scaling_factor = config.routed_scaling_factor
if self.tp_size > config.num_experts:
raise ValueError(
f"Tensor parallel size {self.tp_size} is greater than "
f"the number of experts {config.num_experts}."
)
# Gate (router) - outputs logits for each expert
self.gate = ReplicatedLinear(
config.hidden_size,
config.num_experts,
bias=False,
quant_config=None,
prefix=add_prefix("gate", prefix),
)
# Expert bias (fp32) - affects selection but not weighting
if config.use_expert_bias:
self.expert_bias = nn.Parameter(
torch.zeros(config.num_experts, dtype=torch.float32)
)
else:
self.register_parameter("expert_bias", None)
# TopK selector with sigmoid scoring
self.topk = TopK(
top_k=config.num_experts_per_tok,
layer_id=layer_idx,
renormalize=config.norm_topk_prob,
scoring_func="sigmoid",
correction_bias=self.expert_bias if config.use_expert_bias else None,
)
# FusedMoE for efficient batched expert computation
# Note: We intentionally do NOT pass routed_scaling_factor to FusedMoE.
# While FusedMoE supports it, passing it there increases numerical
# differences vs HuggingFace (likely due to different code paths in the
# Triton runner when scaling_factor != None). We apply it manually below.
self.experts = FusedMoE(
num_experts=config.num_experts,
top_k=config.num_experts_per_tok,
hidden_size=config.hidden_size,
intermediate_size=config.moe_intermediate_size,
layer_id=layer_idx,
reduce_results=True,
quant_config=quant_config,
prefix=add_prefix("experts", prefix),
)
def forward(self, hidden_states: torch.Tensor) -> torch.Tensor:
"""Optimized expert forward pass using FusedMoE."""
# Get router logits
router_logits, _ = self.gate(hidden_states)
# Select top-k experts with sigmoid scoring
topk_output = self.topk(hidden_states, router_logits)
# Run fused expert computation
final_hidden_states = self.experts(hidden_states, topk_output)
# Apply routed scaling factor (see __init__ comment for why not in FusedMoE)
return final_hidden_states * self.routed_scaling_factor
class Lfm2MoeAttention(nn.Module):
"""Grouped-query attention with RoPE and Q/K layernorm."""
def __init__(
self,
config: Lfm2MoeConfig,
layer_id: int,
quant_config: Optional[QuantizationConfig] = None,
prefix: str = "",
) -> None:
super().__init__()
self.hidden_size = config.hidden_size
self.total_num_heads = config.num_attention_heads
self.total_num_kv_heads = config.num_key_value_heads
self.head_dim = self.hidden_size // self.total_num_heads
self.scaling = self.head_dim**-0.5
rope_parameters = getattr(config, "rope_parameters", None)
if rope_parameters is not None and "rope_theta" in rope_parameters:
rope_theta = rope_parameters["rope_theta"]
else:
rope_theta = getattr(config, "rope_theta", 1000000.0)
self.rotary_emb = get_rope(
head_size=self.head_dim,
rotary_dim=self.head_dim,
max_position=getattr(config, "max_position_embeddings", 128000),
rope_scaling=getattr(config, "rope_scaling", None),
base=rope_theta,
is_neox_style=True,
dtype=torch.get_default_dtype(),
)
self.qkv_proj = QKVParallelLinear(
self.hidden_size,
self.head_dim,
self.total_num_heads,
self.total_num_kv_heads,
bias=False,
quant_config=quant_config,
prefix=add_prefix("qkv_proj", prefix),
)
self.out_proj = RowParallelLinear(
self.total_num_heads * self.head_dim,
self.hidden_size,
bias=False,
quant_config=quant_config,
prefix=add_prefix("out_proj", prefix),
)
self.q_layernorm = RMSNorm(self.head_dim, eps=config.norm_eps)
self.k_layernorm = RMSNorm(self.head_dim, eps=config.norm_eps)
self.num_local_q_heads = self.qkv_proj.num_heads
self.num_local_kv_heads = self.qkv_proj.num_kv_heads
self.attn = RadixAttention(
num_heads=self.num_local_q_heads,
head_dim=self.head_dim,
scaling=self.scaling,
num_kv_heads=self.num_local_kv_heads,
layer_id=layer_id,
prefix=add_prefix("attn", prefix),
)
def forward(
self,
positions: torch.Tensor,
hidden_states: torch.Tensor,
forward_batch: ForwardBatch,
) -> torch.Tensor:
T = hidden_states.shape[0]
qkv, _ = self.qkv_proj(hidden_states)
q_size = self.num_local_q_heads * self.head_dim
kv_size = self.num_local_kv_heads * self.head_dim
q, k, v = torch.split(qkv, [q_size, kv_size, kv_size], dim=-1)
q = q.reshape(T, self.num_local_q_heads, self.head_dim)
k = k.reshape(T, self.num_local_kv_heads, self.head_dim)
q = self.q_layernorm(q.reshape(-1, self.head_dim)).reshape(
T, self.num_local_q_heads, self.head_dim
)
k = self.k_layernorm(k.reshape(-1, self.head_dim)).reshape(
T, self.num_local_kv_heads, self.head_dim
)
q, k = self.rotary_emb(positions, q, k)
attn_out = self.attn(q.reshape(T, -1), k.reshape(T, -1), v, forward_batch)
out, _ = self.out_proj(attn_out)
return out
class Lfm2MoeShortConv(nn.Module):
"""
Gated short convolution layer using optimized causal_conv1d kernels.
Architecture: in_proj -> split(B, C, x) -> Bx -> conv1d -> C*conv_out -> out_proj
- Supports tensor parallelism: hidden dimension is sharded across TP ranks
"""
def __init__(
self,
config: Lfm2MoeConfig,
layer_idx: int,
quant_config: Optional[QuantizationConfig] = None,
prefix: str = "",
):
super().__init__()
self.layer_idx = layer_idx
self.conv_kernel = int(config.conv_L_cache)
self.use_bias = bool(config.conv_bias)
self.hidden_size = config.hidden_size
# Get tensor parallel size for sharding
self.tp_size = get_tensor_model_parallel_world_size()
self.hidden_size_per_partition = self.hidden_size // self.tp_size
# Use MergedColumnParallelLinear so each output (B, C, x) is sharded separately
self.in_proj = MergedColumnParallelLinear(
config.hidden_size,
[config.hidden_size] * 3, # B, C, x each get hidden_size
bias=self.use_bias,
quant_config=quant_config,
prefix=f"{prefix}.in_proj",
)
self.out_proj = RowParallelLinear(
config.hidden_size,
config.hidden_size,
bias=self.use_bias,
input_is_parallel=True,
quant_config=quant_config,
prefix=f"{prefix}.out_proj",
)
# Conv weights sharded along hidden dimension: (hidden_size/tp, kernel_size)
self.conv_weight = nn.Parameter(
torch.empty(self.hidden_size_per_partition, self.conv_kernel)
)
set_weight_attrs(self.conv_weight, {"weight_loader": sharded_weight_loader(0)})
if self.use_bias:
self.conv_bias = nn.Parameter(torch.empty(self.hidden_size_per_partition))
set_weight_attrs(
self.conv_bias, {"weight_loader": sharded_weight_loader(0)}
)
else:
self.register_parameter("conv_bias", None)
def forward(
self,
hidden_states: torch.Tensor,
forward_batch: ForwardBatch,
) -> torch.Tensor:
if forward_batch.forward_mode.is_idle():
return hidden_states
layer_cache = forward_batch.req_to_token_pool.mamba2_layer_cache(self.layer_idx)
conv_state = layer_cache.conv[0]
req_pool_indices = forward_batch.req_pool_indices
proj, _ = self.in_proj(hidden_states)
B_gate, C_gate, x = proj.chunk(3, dim=-1)
Bx = B_gate * x
if forward_batch.forward_mode.is_decode():
conv_out = causal_conv1d_update(
Bx,
conv_state,
self.conv_weight,
self.conv_bias,
activation=None,
conv_state_indices=req_pool_indices.to(torch.int32),
)
else:
T = hidden_states.shape[0]
Bx_t = Bx.transpose(0, 1).contiguous()
# Build query_start_loc for variable-length sequences
# causal_conv1d_fn expects [start0, start1, ..., startN, T]
extend_start_loc = forward_batch.extend_start_loc
if extend_start_loc is not None and len(extend_start_loc) > 1:
# Multiple sequences: append T to extend_start_loc
# Allocate and fill to avoid torch.cat overhead
query_start_loc = extend_start_loc.new_empty(len(extend_start_loc) + 1)
query_start_loc[:-1] = extend_start_loc
query_start_loc[-1] = T
cache_indices = req_pool_indices.to(torch.int32)
else:
# Single sequence: [0, T]
query_start_loc = hidden_states.new_tensor([0, T], dtype=torch.int32)
cache_indices = req_pool_indices[:1].to(torch.int32)
conv_out = causal_conv1d_fn(
Bx_t,
self.conv_weight,
self.conv_bias,
query_start_loc=query_start_loc,
cache_indices=cache_indices,
has_initial_state=None,
conv_states=conv_state,
activation=None,
).transpose(0, 1)
output, _ = self.out_proj(C_gate * conv_out)
return output
class Lfm2MoeDecoderLayer(nn.Module):
"""
Decoder layer with attention/conv and dense MLP or MoE.
- Layers 0 to num_dense_layers-1: use Lfm2MoeMLP (dense)
- Layers num_dense_layers+: use Lfm2MoeSparseMoeBlock (MoE)
"""
def __init__(
self,
config: Lfm2MoeConfig,
layer_id: int,
quant_config: Optional[QuantizationConfig] = None,
prefix: str = "",
):
super().__init__()
self.layer_type = config.layer_types[layer_id]
self.is_attention_layer = self.layer_type == "full_attention"
self.operator_norm = RMSNorm(config.hidden_size, eps=config.norm_eps)
self.ffn_norm = RMSNorm(config.hidden_size, eps=config.norm_eps)
# Attention or Conv
if self.is_attention_layer:
self.self_attn = Lfm2MoeAttention(
config=config,
layer_id=layer_id,
quant_config=quant_config,
prefix=add_prefix("self_attn", prefix),
)
else:
self.conv = Lfm2MoeShortConv(
config=config,
layer_idx=layer_id,
quant_config=quant_config,
prefix=add_prefix("conv", prefix),
)
# Dense MLP or MoE
if layer_id < config.num_dense_layers:
self.feed_forward = Lfm2MoeMLP(
config=config,
quant_config=quant_config,
prefix=add_prefix("feed_forward", prefix),
)
else:
self.feed_forward = Lfm2MoeSparseMoeBlock(
config=config,
layer_idx=layer_id,
quant_config=quant_config,
prefix=add_prefix("feed_forward", prefix),
)
def forward(
self,
layer_id: int,
positions: torch.Tensor,
hidden_states: torch.Tensor,
residual: Optional[torch.Tensor],
forward_batch: ForwardBatch,
**kwargs,
) -> Tuple[torch.Tensor, torch.Tensor]:
if not forward_batch.forward_mode.is_idle():
residual = hidden_states
normed = self.operator_norm(hidden_states)
if self.is_attention_layer:
hidden_states = self.self_attn(positions, normed, forward_batch)
else:
hidden_states = self.conv(normed, forward_batch)
hidden_states = hidden_states + residual
hidden_states = hidden_states + self.feed_forward(
self.ffn_norm(hidden_states)
)
return hidden_states, residual
class Lfm2MoeModel(nn.Module):
def __init__(
self,
config: Lfm2MoeConfig,
quant_config: Optional[QuantizationConfig] = None,
prefix: str = "",
):
super().__init__()
self.config = config
self.embed_tokens = VocabParallelEmbedding(
config.vocab_size,
config.hidden_size,
org_num_embeddings=config.vocab_size,
prefix=add_prefix("embed_tokens", prefix),
)
# Count attention layers for KV cache sizing
self.num_attention_layers = sum(
1 for lt in config.layer_types if lt == "full_attention"
)
def get_layer(idx: int, prefix: str, **kwargs):
return Lfm2MoeDecoderLayer(
config=config,
layer_id=idx,
quant_config=quant_config,
prefix=prefix,
)
self.layers = make_layers(
config.num_hidden_layers, get_layer, prefix=f"{prefix}.layers"
)
self.embedding_norm = RMSNorm(config.hidden_size, eps=config.norm_eps)
def forward(
self,
input_ids: torch.Tensor,
positions: torch.Tensor,
forward_batch: ForwardBatch,
inputs_embeds: Optional[torch.Tensor] = None,
) -> torch.Tensor:
hidden_states = (
inputs_embeds if inputs_embeds is not None else self.embed_tokens(input_ids)
)
residual = None
for i in range(len(self.layers)):
hidden_states, residual = self.layers[i](
layer_id=i,
positions=positions,
hidden_states=hidden_states,
residual=residual,
forward_batch=forward_batch,
)
return self.embedding_norm(hidden_states)
class Lfm2MoeForCausalLM(nn.Module):
"""LFM2-MoE for causal language modeling."""
fall_back_to_pt_during_load = False
def __init__(
self,
config: Lfm2MoeConfig,
quant_config: Optional[QuantizationConfig] = None,
prefix: str = "",
) -> None:
super().__init__()
self.config = config
self.pp_group = get_pp_group()
assert self.pp_group.is_first_rank and self.pp_group.is_last_rank
self.quant_config = quant_config
self.model = Lfm2MoeModel(
config, quant_config, prefix=add_prefix("model", prefix)
)
self.lm_head = ParallelLMHead(
config.vocab_size,
config.hidden_size,
quant_config=quant_config,
org_num_embeddings=config.vocab_size,
prefix=add_prefix("lm_head", prefix),
)
self.logits_processor = LogitsProcessor(config)
self.num_attention_layers = self.model.num_attention_layers
def get_num_kv_cache_layers(self) -> int:
return self.num_attention_layers
@torch.no_grad()
def forward(
self,
input_ids: torch.Tensor,
positions: torch.Tensor,
forward_batch: ForwardBatch,
inputs_embeds: Optional[torch.Tensor] = None,
**kwargs,
):
hidden_states = self.model(input_ids, positions, forward_batch, inputs_embeds)
return self.logits_processor(
input_ids, hidden_states, self.lm_head, forward_batch
)
def load_weights(
self, weights: Iterable[Tuple[str, torch.Tensor]], is_mtp: bool = False
) -> Set[str]:
"""Load weights with FusedMoE expert format."""
stacked_params_mapping = [
# (param_name, weight_name, shard_id)
("qkv_proj", "q_proj", "q"),
("qkv_proj", "k_proj", "k"),
("qkv_proj", "v_proj", "v"),
# Dense MLP w1/w3 -> gate_up_proj
("gate_up_proj", "w1", 0),
("gate_up_proj", "w3", 1),
]
# FusedMoE expert params mapping
# HF format: experts.{expert_id}.w{1,2,3}.weight
# FusedMoE format: experts.w13_weight, experts.w2_weight
expert_params_mapping = FusedMoE.make_expert_params_mapping(
ckpt_gate_proj_name="w1",
ckpt_down_proj_name="w2",
ckpt_up_proj_name="w3",
num_experts=self.config.num_experts,
)
params_dict = dict(self.named_parameters())
loaded_params: Set[str] = set()
embed_tokens_weight = None
for name, loaded_weight in weights:
if "rotary_emb.inv_freq" in name:
continue
if "embed_tokens.weight" in name:
embed_tokens_weight = loaded_weight
# Handle conv weight/bias naming: HF uses conv.conv, we use conv_weight/conv_bias
if ".conv.conv.weight" in name:
name = name.replace(".conv.conv.weight", ".conv.conv_weight")
loaded_weight = loaded_weight.squeeze(1) # (D, 1, K) -> (D, K)
if ".conv.conv.bias" in name:
name = name.replace(".conv.conv.bias", ".conv.conv_bias")
# Handle dense MLP w2 -> down_proj
if "feed_forward.w2" in name and "experts" not in name:
name = name.replace("feed_forward.w2", "feed_forward.down_proj")
# Handle stacked params (QKV, dense MLP gate_up)
for param_name, weight_name, shard_id in stacked_params_mapping:
if weight_name not in name:
continue
# Skip expert weights (handled below)
if "experts" in name:
continue
name = name.replace(weight_name, param_name)
if name.endswith(".bias") and name not in params_dict:
break
if name not in params_dict:
break
param = params_dict[name]
weight_loader = getattr(param, "weight_loader")
weight_loader(param, loaded_weight, shard_id)
loaded_params.add(name)
break
else:
# Handle MoE expert weights using FusedMoE format
# HF format: model.layers.X.feed_forward.experts.Y.wZ.weight
# FusedMoE format: model.layers.X.feed_forward.experts.w13_weight/w2_weight
for (
param_name,
weight_name,
expert_id,
shard_id,
) in expert_params_mapping:
if weight_name not in name:
continue
# Build our parameter name
name = name.replace(weight_name, param_name)
if name not in params_dict:
continue
param = params_dict[name]
weight_loader = param.weight_loader
weight_loader(
param,
loaded_weight,
name,
shard_id=shard_id,
expert_id=expert_id,
)
loaded_params.add(name)
break
else:
# Handle regular weights
if name.endswith(".bias") and name not in params_dict:
continue
if name not in params_dict:
continue
param = params_dict[name]
weight_loader = getattr(
param, "weight_loader", default_weight_loader
)
weight_loader(param, loaded_weight)
loaded_params.add(name)
# Handle tied lm_head weight
if "lm_head.weight" not in loaded_params and "lm_head.weight" in params_dict:
if embed_tokens_weight is not None:
param = params_dict["lm_head.weight"]
weight_loader = getattr(param, "weight_loader", default_weight_loader)
weight_loader(param, embed_tokens_weight)
loaded_params.add("lm_head.weight")
return loaded_params
EntryClass = [Lfm2MoeForCausalLM]