Files
sglang/python/sglang/srt/layers/utils/logprob.py
Qiaolin Yu 09a118fafe Support return_logprob for spec v2 (overlap safe) (#19801)
Co-authored-by: Ratish1 <ratish1501@gmail.com>
Co-authored-by: Ratish1 <formula733@gmail.com>
Co-authored-by: hnyls2002 <lsyincs@gmail.com>
2026-03-10 15:38:27 -07:00

426 lines
14 KiB
Python

from __future__ import annotations
import dataclasses
from enum import Enum, auto
from typing import TYPE_CHECKING, List, Optional, Union
import torch
from sglang.srt.environ import envs
if TYPE_CHECKING:
from sglang.srt.layers.logits_processor import LogitsMetadata, LogitsProcessorOutput
from sglang.srt.managers.schedule_batch import ScheduleBatch
from sglang.srt.speculative.eagle_info import EagleVerifyOutput
from sglang.srt.speculative.ngram_info import NgramVerifyInput
class LogprobStage(Enum):
PREFILL = auto()
DECODE = auto()
@dataclasses.dataclass
class InputLogprobsResult:
input_token_logprobs: torch.Tensor
input_top_logprobs_val: Optional[List] = None
input_top_logprobs_idx: Optional[List] = None
input_token_ids_logprobs_val: Optional[List] = None
input_token_ids_logprobs_idx: Optional[List] = None
def compute_temp_top_p_normalized_logprobs(
last_logits: torch.Tensor,
logits_metadata: LogitsMetadata,
top_p: Optional[torch.Tensor] = None,
temperature: Optional[torch.Tensor] = None,
) -> torch.Tensor:
"""
compute logprobs for the output token from the given logits.
Returns:
torch.Tensor: logprobs from logits
"""
if top_p is None:
top_p = logits_metadata.top_p
if temperature is None:
temperature = logits_metadata.temperature
# Scale logits if temperature scaling is enabled
if logits_metadata.temp_scaled_logprobs:
last_logits = last_logits / temperature
# Normalize logprobs if top_p normalization is enabled
# NOTE: only normalize logprobs when top_p is set and not equal to 1.0
if logits_metadata.top_p_normalized_logprobs and (top_p != 1.0).any():
from sglang.srt.layers.sampler import top_p_normalize_probs_torch
probs = torch.softmax(last_logits, dim=-1)
del last_logits
probs = top_p_normalize_probs_torch(probs, top_p)
return torch.log(probs)
else:
return torch.nn.functional.log_softmax(last_logits, dim=-1)
def get_top_logprobs_raw(
logprobs: torch.Tensor,
top_logprobs_nums: List[int],
stage: LogprobStage,
extend_logprob_pruned_lens_cpu: Optional[List[int]] = None,
no_copy_to_cpu: bool = False,
):
max_k = max(top_logprobs_nums)
values, indices = logprobs.topk(max_k, dim=-1)
if not no_copy_to_cpu:
values = values.tolist()
indices = indices.tolist()
top_logprobs_val = []
top_logprobs_idx = []
if stage == LogprobStage.DECODE:
for i, k in enumerate(top_logprobs_nums):
top_logprobs_val.append(values[i][:k])
top_logprobs_idx.append(indices[i][:k])
else:
pt = 0
for k, pruned_len in zip(top_logprobs_nums, extend_logprob_pruned_lens_cpu):
if pruned_len <= 0:
top_logprobs_val.append([])
top_logprobs_idx.append([])
continue
top_logprobs_val.append([values[pt + j][:k] for j in range(pruned_len)])
top_logprobs_idx.append([indices[pt + j][:k] for j in range(pruned_len)])
pt += pruned_len
return top_logprobs_val, top_logprobs_idx
def get_top_logprobs_prefill(
all_logprobs: torch.Tensor, logits_metadata: LogitsMetadata
):
return get_top_logprobs_raw(
all_logprobs,
logits_metadata.top_logprobs_nums,
stage=LogprobStage.PREFILL,
extend_logprob_pruned_lens_cpu=logits_metadata.extend_logprob_pruned_lens_cpu,
)
def get_top_logprobs(
logprobs: torch.Tensor,
top_logprobs_nums: List[int],
no_copy_to_cpu: bool = False,
):
return get_top_logprobs_raw(
logprobs,
top_logprobs_nums,
stage=LogprobStage.DECODE,
no_copy_to_cpu=no_copy_to_cpu,
)
def get_token_ids_logprobs_raw(
logprobs: torch.Tensor,
token_ids_logprobs_list: List[Optional[List[int]]],
stage: LogprobStage,
extend_logprob_pruned_lens_cpu: Optional[List[int]] = None,
no_copy_to_cpu: bool = False,
):
vals, idxs = [], []
if stage == LogprobStage.DECODE:
for i, token_ids in enumerate(token_ids_logprobs_list):
if token_ids is None:
vals.append([])
idxs.append([])
else:
token_ids_tensor = torch.tensor(token_ids, dtype=torch.long).to(
logprobs.device, non_blocking=True
)
row = logprobs[i, token_ids_tensor]
vals.append(row if no_copy_to_cpu else row.tolist())
idxs.append(token_ids)
else: # prefill
pt = 0
for i, (token_ids, pruned_len) in enumerate(
zip(token_ids_logprobs_list, extend_logprob_pruned_lens_cpu)
):
if pruned_len <= 0:
vals.append([])
idxs.append([])
continue
token_ids_tensor = torch.tensor(token_ids, dtype=torch.long).to(
logprobs.device, non_blocking=True
)
pos_logprobs = logprobs[pt : pt + pruned_len, token_ids_tensor]
vals.append(pos_logprobs if no_copy_to_cpu else pos_logprobs.tolist())
idxs.append([token_ids for _ in range(pruned_len)])
pt += pruned_len
return vals, idxs
def get_token_ids_logprobs_prefill(
all_logprobs, logits_metadata: LogitsMetadata, no_copy_to_cpu=False
):
return get_token_ids_logprobs_raw(
all_logprobs,
logits_metadata.token_ids_logprobs,
stage=LogprobStage.PREFILL,
extend_logprob_pruned_lens_cpu=logits_metadata.extend_logprob_pruned_lens_cpu,
no_copy_to_cpu=no_copy_to_cpu,
)
def get_token_ids_logprobs(logprobs, token_ids_logprobs, no_copy_to_cpu=False):
return get_token_ids_logprobs_raw(
logprobs,
token_ids_logprobs,
stage=LogprobStage.DECODE,
no_copy_to_cpu=no_copy_to_cpu,
)
def get_top_logprobs_chunk(
logprobs: torch.Tensor,
logits_metadata: LogitsMetadata,
top_k_nums: List[int],
pruned_lens: List[int],
input_top_logprobs_val: List,
input_top_logprobs_idx: List,
split_pruned_len: int,
) -> int:
"""Get top-k logprobs for each sequence in the chunk.
Args:
logprobs: Log probabilities tensor of shape [seq_len, vocab_size]
logits_metadata: Metadata containing top-k and pruned length info
top_k_nums: List of top-k numbers for each sequence
pruned_lens: List of pruned lengths for each sequence
input_top_logprobs_val: List to store top-k logprob values
input_top_logprobs_idx: List to store top-k token indices
split_pruned_len: Length of pruned tokens from previous chunk
Returns:
int: Number of remaining tokens to process in next chunk
"""
# No sequences in the chunk
if logprobs.shape[0] == 0:
return 0
max_k = max(logits_metadata.top_logprobs_nums)
ret = logprobs.topk(max_k, dim=1)
values = ret.values.tolist()
indices = ret.indices.tolist()
pt = 0
next_split_pruned_len = 0
for n, (k, pruned_len) in enumerate(zip(top_k_nums, pruned_lens)):
if n == 0:
# For the first sequence, adjust the pruned length
pruned_len -= split_pruned_len
else:
# After the first sequence, no split in the middle
split_pruned_len = 0
if pruned_len <= 0:
# if pruned length is less than or equal to 0,
# there is no top-k logprobs to process
input_top_logprobs_val.append([])
input_top_logprobs_idx.append([])
continue
# Get the top-k logprobs
val = []
idx = []
for j in range(pruned_len):
# Handle remaining tokens in next chunk if any
if pt + j >= len(values):
next_split_pruned_len = split_pruned_len + j
break
# Append the top-k logprobs
val.append(values[pt + j][:k])
idx.append(indices[pt + j][:k])
# Append or extend based on whether the sequence was split across chunks
if len(val) > 0:
if split_pruned_len > 0:
input_top_logprobs_val[-1].extend(val)
input_top_logprobs_idx[-1].extend(idx)
else:
input_top_logprobs_val.append(val)
input_top_logprobs_idx.append(idx)
pt += pruned_len
return next_split_pruned_len
def get_token_ids_logprobs_chunk(
logprobs: torch.Tensor,
token_ids_logprobs: List[int],
pruned_lens: List[int],
input_token_ids_logprobs_val: List,
input_token_ids_logprobs_idx: List,
split_pruned_len: int = 0,
):
"""Get token_ids logprobs for each sequence in the chunk.
Args:
logprobs: Log probabilities tensor of shape [seq_len, vocab_size]
logits_metadata: Metadata containing token IDs and pruned length info
token_ids_logprobs: List of token IDs for each sequence
pruned_lens: List of pruned lengths for each sequence
input_token_ids_logprobs_val: List to store token logprob values
input_token_ids_logprobs_idx: List to store token indices
split_pruned_len: Length of pruned tokens from previous chunk
Returns:
int: Number of remaining tokens to process in next chunk
"""
# No sequences in the chunk
if logprobs.shape[0] == 0:
return 0
pt = 0
next_split_pruned_len = 0
for n, (token_ids, pruned_len) in enumerate(
zip(
token_ids_logprobs,
pruned_lens,
)
):
# Adjust pruned length for first sequence
if n == 0:
pruned_len -= split_pruned_len
else:
split_pruned_len = 0
if pruned_len <= 0:
# if pruned length is less than or equal to 0,
# there is no token ids logprobs to process
input_token_ids_logprobs_val.append([])
input_token_ids_logprobs_idx.append([])
continue
# Get the token ids logprobs
val = []
idx = []
for j in range(pruned_len):
# Handle remaining tokens in next chunk if any
if pt + j >= logprobs.shape[0]:
next_split_pruned_len = split_pruned_len + j
break
if token_ids is not None:
val.append(logprobs[pt + j, token_ids].tolist())
idx.append(token_ids)
# Append or extend based on whether the sequence was split across chunks
if len(val) > 0:
if split_pruned_len > 0:
input_token_ids_logprobs_val[-1].extend(val)
input_token_ids_logprobs_idx[-1].extend(idx)
else:
input_token_ids_logprobs_val.append(val)
input_token_ids_logprobs_idx.append(idx)
pt += pruned_len
return next_split_pruned_len
def add_output_logprobs_for_spec_v1(
batch: ScheduleBatch,
res: Union[EagleVerifyOutput, NgramVerifyInput],
logits_output: Optional[LogitsProcessorOutput] = None,
):
# Extract args
if logits_output is None:
logits_output = res.logits_output
if hasattr(res, "accept_length_per_req_cpu"):
accept_length_per_req_cpu = res.accept_length_per_req_cpu
else:
# FIXME: Get a NgramVerifyOutput class and use that instead of this hack.
accept_length_per_req_cpu = res.accept_length.tolist()
top_logprobs_nums = batch.top_logprobs_nums
token_ids_logprobs = batch.token_ids_logprobs
accepted_indices = res.accepted_indices
assert len(accepted_indices) == len(logits_output.next_token_logits)
temperatures = batch.sampling_info.temperatures
num_draft_tokens = batch.spec_info.draft_token_num
# acceptance indices are the indices in a "flattened" batch.
# dividing it to num_draft_tokens will yield the actual batch index.
temperatures = temperatures[accepted_indices // num_draft_tokens]
if envs.SGLANG_RETURN_ORIGINAL_LOGPROB.get():
logprobs = torch.nn.functional.log_softmax(
logits_output.next_token_logits, dim=-1
)
else:
logprobs = torch.nn.functional.log_softmax(
logits_output.next_token_logits / temperatures, dim=-1
)
batch_next_token_ids = res.verified_id
num_tokens_per_req = [accept + 1 for accept in accept_length_per_req_cpu]
# We should repeat top_logprobs_nums to match num_tokens_per_req.
top_logprobs_nums_repeat_interleaved = [
num
for num, num_tokens in zip(top_logprobs_nums, num_tokens_per_req)
for _ in range(num_tokens)
]
token_ids_logprobs_repeat_interleaved = [
token_ids
for token_ids, num_tokens in zip(token_ids_logprobs, num_tokens_per_req)
for _ in range(num_tokens)
]
# Extract logprobs
should_top_logprobs = any(x > 0 for x in top_logprobs_nums)
should_token_ids_logprobs = any(x is not None for x in token_ids_logprobs)
if should_top_logprobs:
(
logits_output.next_token_top_logprobs_val,
logits_output.next_token_top_logprobs_idx,
) = get_top_logprobs(
logprobs,
top_logprobs_nums_repeat_interleaved,
)
if should_token_ids_logprobs:
(
logits_output.next_token_token_ids_logprobs_val,
logits_output.next_token_token_ids_logprobs_idx,
) = get_token_ids_logprobs(
logprobs,
token_ids_logprobs_repeat_interleaved,
)
logits_output.next_token_logprobs = logprobs[
torch.arange(len(batch_next_token_ids), device=batch.sampling_info.device),
batch_next_token_ids,
]
# Add output logprobs to the request
pt = 0
next_token_logprobs = logits_output.next_token_logprobs.tolist()
verified_ids = batch_next_token_ids.tolist()
token_top_logprobs_val = logits_output.next_token_top_logprobs_val
token_top_logprobs_idx = logits_output.next_token_top_logprobs_idx
for req, num_tokens in zip(batch.reqs, num_tokens_per_req, strict=True):
for _ in range(num_tokens):
# TODO: add token_ids_logprobs to each request
if req.return_logprob:
req.output_token_logprobs_val.append(next_token_logprobs[pt])
req.output_token_logprobs_idx.append(verified_ids[pt])
if req.top_logprobs_num > 0:
assert (
should_top_logprobs
), "Inconsistent state: should_top_logprobs is False"
req.output_top_logprobs_val.append(token_top_logprobs_val[pt])
req.output_top_logprobs_idx.append(token_top_logprobs_idx[pt])
pt += 1