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sglang/python/sglang/srt/models/utils.py
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# Copyright 2023-2025 SGLang Team
# 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.
# ==============================================================================
from __future__ import annotations
from collections.abc import Iterable, Mapping
from dataclasses import dataclass, field
from functools import lru_cache
from typing import TYPE_CHECKING, Any, Optional, Tuple
import numpy as np
import torch
from sglang.jit_kernel.norm import can_use_fused_inplace_qknorm, fused_inplace_qknorm
from sglang.srt.environ import envs
from sglang.srt.layers.radix_attention import RadixAttention
from sglang.srt.model_executor.cuda_graph_runner import get_is_capture_mode
from sglang.srt.model_executor.forward_batch_info import ForwardBatch
from sglang.srt.utils import is_cuda
from sglang.srt.utils.custom_op import register_custom_op
if TYPE_CHECKING:
from sglang.srt.layers.layernorm import RMSNorm
_is_cuda = is_cuda()
WeightsMapping = Mapping[str, Optional[str]]
"""If a key maps to a value of `None`, the corresponding weight is ignored."""
@dataclass
class WeightsMapper:
"""Maps the name of each weight if they match the following patterns."""
orig_to_new_substr: WeightsMapping = field(default_factory=dict)
orig_to_new_prefix: WeightsMapping = field(default_factory=dict)
orig_to_new_suffix: WeightsMapping = field(default_factory=dict)
def _map_name(self, key: str) -> Optional[str]:
for substr, new_key in sorted(
self.orig_to_new_substr.items(), key=lambda i: len(i[0]), reverse=True
):
if substr in key:
if new_key is None:
return None
key = key.replace(substr, new_key, 1)
break
for prefix, new_key in sorted(
self.orig_to_new_prefix.items(), key=lambda i: len(i[0]), reverse=True
):
if key.startswith(prefix):
if new_key is None:
return None
key = key.replace(prefix, new_key, 1)
break
for suffix, new_key in sorted(
self.orig_to_new_suffix.items(), key=lambda i: len(i[0]), reverse=True
):
if key.endswith(suffix):
if new_key is None:
return None
key = new_key.join(key.rsplit(suffix, 1))
break
return key
def apply(
self, weights: Iterable[tuple[str, torch.Tensor]]
) -> Iterable[tuple[str, torch.Tensor]]:
return (
(out_name, data)
for name, data in weights
if (out_name := self._map_name(name)) is not None
)
def apply_list(self, values: list[str]) -> list[str]:
return [
out_name
for name in values
if (out_name := self._map_name(name)) is not None
]
def apply_dict(self, values: dict[str, Any]) -> dict[str, Any]:
return {
out_name: value
for name, value in values.items()
if (out_name := self._map_name(name)) is not None
}
def enable_fused_set_kv_buffer(forward_batch: ForwardBatch):
"""Enable fused set_kv_buffer only on CUDA with bfloat16 KV cache."""
return (
_is_cuda
and hasattr(forward_batch.token_to_kv_pool, "dtype")
and forward_batch.token_to_kv_pool.dtype == torch.bfloat16
)
def create_fused_set_kv_buffer_arg(
value: torch.Tensor,
layer: RadixAttention,
forward_batch: ForwardBatch,
):
from sgl_kernel import FusedSetKVBufferArg
layer_id = layer.layer_id
token_to_kv_pool = forward_batch.token_to_kv_pool
k_buffer = token_to_kv_pool.get_key_buffer(layer_id)
v_buffer = token_to_kv_pool.get_value_buffer(layer_id)
return FusedSetKVBufferArg(
value=value,
k_buffer=k_buffer.view(k_buffer.shape[0], -1),
v_buffer=v_buffer.view(v_buffer.shape[0], -1),
k_scale=layer.k_scale,
v_scale=layer.v_scale,
cache_loc=forward_batch.out_cache_loc,
)
def permute_inv(perm: torch.Tensor) -> torch.Tensor:
inv_perm = torch.empty_like(perm)
inv_perm[perm] = torch.arange(perm.numel(), device=perm.device, dtype=perm.dtype)
return inv_perm
def compute_cu_seqlens_from_grid_numpy(grid_thw: torch.Tensor) -> torch.Tensor:
"""
Compute cu_seqlens from grid_thw using NumPy.
grid_thw: [T, 3] int tensor on CPU.
columns: [repeat_count, H, W]
Returns:
cu_seqlens: 1D int32 tensor on CPU, shape [N + 1]
"""
assert (
grid_thw.device.type == "cpu"
), "compute_cu_seqlens_from_grid_numpy expects a CPU tensor"
arr = grid_thw.numpy()
cu_seqlens = np.repeat(arr[:, 1] * arr[:, 2], arr[:, 0]).cumsum(
axis=0, dtype=np.int32
)
cu_seqlens = np.concatenate([np.zeros(1, dtype=np.int32), cu_seqlens])
cu_seqlens = torch.from_numpy(cu_seqlens)
return cu_seqlens
class RotaryPosMixin:
@staticmethod
@lru_cache(maxsize=1024)
def rot_pos_ids(h: int, w: int, spatial_merge_size: int) -> torch.Tensor:
if isinstance(h, torch.Tensor):
h = int(h.item())
if isinstance(w, torch.Tensor):
w = int(w.item())
if isinstance(spatial_merge_size, torch.Tensor):
spatial_merge_size = int(spatial_merge_size.item())
hpos_ids = np.broadcast_to(np.arange(h).reshape(h, 1), (h, w))
h_div = h // spatial_merge_size
w_div = w // spatial_merge_size
hpos_ids = hpos_ids.reshape(
h_div,
spatial_merge_size,
w_div,
spatial_merge_size,
)
hpos_ids = hpos_ids.transpose(0, 2, 1, 3)
hpos_ids = hpos_ids.flatten()
wpos_ids = np.broadcast_to(np.arange(w).reshape(1, w), (h, w))
wpos_ids = wpos_ids.reshape(
h_div,
spatial_merge_size,
w_div,
spatial_merge_size,
)
wpos_ids = wpos_ids.transpose(0, 2, 1, 3)
wpos_ids = wpos_ids.flatten()
return torch.from_numpy(np.stack([hpos_ids, wpos_ids], axis=-1))
def apply_qk_norm(
q: torch.Tensor,
k: torch.Tensor,
q_norm: RMSNorm,
k_norm: RMSNorm,
head_dim: int,
alt_stream: Optional[torch.cuda.Stream] = None,
allow_inplace: bool = True,
) -> Tuple[torch.Tensor, torch.Tensor]:
"""
Apply QK normalization for query and key tensors.
If eligible, we will use JIT fused inplace QK normalization for better performance.
Args:
q: Query tensor of shape [batch_size, ...]
k: Key tensor of shape [batch_size, ...]
q_norm: RMSNorm layer for query normalization
k_norm: RMSNorm layer for key normalization
head_dim: Dimension of each attention head
alt_stream: Optional alternative CUDA stream for overlapping computation
allow_inplace: Whether to allow inplace normalization. (True for better performance)
Returns:
Tuple of normalized query and key tensors
"""
batch_size = q.size(0)
q_eps = q_norm.variance_epsilon
k_eps = k_norm.variance_epsilon
if (
_is_cuda # TODO(dark): have not tested on ROCm or other backends
and allow_inplace # TODO(dark): this can be relaxed if needed
and (q_eps == k_eps) # TODO(dark): this can also be relaxed
and not envs.SGLANG_ENABLE_DETERMINISTIC_INFERENCE.get()
and can_use_fused_inplace_qknorm(head_dim)
):
fused_inplace_qknorm(
q=q.view(batch_size, -1, head_dim),
k=k.view(batch_size, -1, head_dim),
q_weight=q_norm.weight,
k_weight=k_norm.weight,
head_dim=head_dim,
eps=q_eps,
)
return q, k
if alt_stream is not None and get_is_capture_mode():
current_stream = torch.cuda.current_stream()
alt_stream.wait_stream(current_stream)
q_by_head = q.reshape(-1, head_dim)
q_by_head = q_norm(q_by_head)
with torch.cuda.stream(alt_stream):
k_by_head = k.reshape(-1, head_dim)
k_by_head = k_norm(k_by_head)
current_stream.wait_stream(alt_stream)
else:
q_by_head = q.reshape(-1, head_dim)
q_by_head = q_norm(q_by_head)
k_by_head = k.reshape(-1, head_dim)
k_by_head = k_norm(k_by_head)
q = q_by_head.view(q.shape)
k = k_by_head.view(k.shape)
return q, k
# Register the inplace op
fused_inplace_qknorm = register_custom_op(fused_inplace_qknorm, mutates_args=["q", "k"])