afeldman-nm bf7f470b22
[V1] Logits processors extensibility (#19912)
Signed-off-by: Andrew Feldman <afeldman@redhat.com>
Signed-off-by: Andrew Feldman <afeld2012@gmail.com>
Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>
Signed-off-by: Nick Hill <nhill@redhat.com>
Co-authored-by: Nick Hill <nhill@redhat.com>
Co-authored-by: Andrew Feldman <afeld2012@gmail.com>
Co-authored-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>
2025-08-16 12:59:17 -07:00

87 lines
2.6 KiB
Python

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
from abc import ABC, abstractmethod
from collections.abc import Sequence
from dataclasses import dataclass
from enum import Enum, auto
from typing import TYPE_CHECKING, Optional
import torch
from vllm import SamplingParams
if TYPE_CHECKING:
from vllm.config import VllmConfig
class MoveDirectionality(Enum):
# One-way i1->i2 req move within batch
UNIDIRECTIONAL = auto()
# Two-way i1<->i2 req swap within batch
SWAP = auto()
# (index, params, prompt_tok_ids, output_tok_ids) tuples for new
# requests added to the batch.
AddedRequest = tuple[int, SamplingParams, list[int], list[int]]
# (index 1, index 2, directionality) tuples representing
# one-way moves or two-way swaps of requests in batch
MovedRequest = tuple[int, int, MoveDirectionality]
# Batch indices of any removed requests.
RemovedRequest = int
@dataclass(frozen=True)
class BatchUpdate:
"""Persistent batch state change info for logitsprocs"""
batch_size: int # Current num reqs in batch
# Metadata for requests added to, removed from, and moved
# within the persistent batch.
#
# Key assumption: the `output_tok_ids` list (which is an element of each
# tuple in `added`) is a reference to the request's running output tokens
# list; via this reference, the logits processors always see the latest
# list of generated output tokens
removed: Sequence[RemovedRequest]
moved: Sequence[MovedRequest]
added: Sequence[AddedRequest]
class LogitsProcessor(ABC):
@abstractmethod
def __init__(self, vllm_config: "VllmConfig", device: torch.device,
is_pin_memory: bool) -> None:
raise NotImplementedError
@abstractmethod
def apply(self, logits: torch.Tensor) -> torch.Tensor:
raise NotImplementedError
@abstractmethod
def is_argmax_invariant(self) -> bool:
"""True if logits processor has no impact on the
argmax computation in greedy sampling.
NOTE: may or may not have the same value for all
instances of a given LogitsProcessor subclass,
depending on subclass implementation.
"""
raise NotImplementedError
@abstractmethod
def update_state(
self,
batch_update: Optional["BatchUpdate"],
) -> None:
"""Called when there are new output tokens, prior
to each forward pass.
Args:
batch_update is non-None iff there have been
changes to the batch makeup.
"""
raise NotImplementedError