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sglang/python/sglang/srt/models/utils.py

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Python

# 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.
# ==============================================================================
import numpy as np
import torch
from sglang.srt.layers.radix_attention import RadixAttention
from sglang.srt.model_executor.forward_batch_info import ForwardBatch
from sglang.srt.utils import is_cuda
_is_cuda = is_cuda()
if _is_cuda:
from sgl_kernel import FusedSetKVBufferArg
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,
):
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