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hao-ai-lab-FastVideo/fastvideo/eval/worker.py
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"""EvalWorker: a single-GPU bag of metric replicas.
One ``EvalWorker`` per GPU. Holds an instance of every requested metric on
its own device, scores one sample at a time. Stateless across calls — the
worker never sees more than one ``evaluate(...)`` invocation at a time
(the parent :class:`Evaluator` ensures this by handing the worker to one
thread at a time).
This mirrors FastVideo's ``Worker`` layer under :class:`VideoGenerator`,
but in-process (threads, not processes) — eval metrics are independent
and need no NCCL / TP / SP / distributed init, so process isolation is
unnecessary overhead.
"""
from __future__ import annotations
import contextlib
from typing import Any
import torch
from fastvideo.eval.memory import clear_cache
from fastvideo.eval.metrics.base import BaseMetric
from fastvideo.eval.registry import get_metric
from fastvideo.eval.types import MetricResult
class EvalWorker:
"""Owns metric replicas on one device. Single-GPU, single-sample.
Per-sample metrics (``is_set_metric=False``) return one
:class:`MetricResult` per ``evaluate`` call. Set metrics
(``is_set_metric=True``) accumulate state on the worker's own
instance and contribute nothing to the per-sample return — the
Evaluator finalizes them after the pool drains.
"""
def __init__(self, metric_names: list[str], device: str, *, compile: bool = False, pre_upload: bool = True) -> None:
self._names = list(metric_names)
self._device = device
self._compile = compile
self._pre_upload = pre_upload
self._metrics: dict[str, BaseMetric] = {}
self._unloaded = False
self._load()
@property
def device(self) -> str:
return self._device
@property
def metric_names(self) -> list[str]:
"""Names of the metrics this worker owns, in load order."""
return list(self._metrics.keys())
def _load(self) -> None:
for name in self._names:
m = get_metric(name)
m.to(self._device)
m.setup()
if self._compile and getattr(m, "_model", None) is not None:
m._model = torch.compile(m._model)
self._metrics[name] = m
# Skip pre_upload when no loaded metric actually runs on GPU
# (e.g. an all-physics_iq run) — it would just pay a wasted
# host→device→host round-trip per sample.
self._any_needs_gpu = any(m.needs_gpu for m in self._metrics.values())
self._unloaded = False
def evaluate(self, **kwargs) -> dict[str, MetricResult]:
"""Score one already-decoded sample.
Inputs (``video`` / ``reference`` paths, 5-D tensors) are
decoded and normalized upstream by the :class:`VideoPool`. The
worker only handles the optional pre-upload to its device and
dispatches to each metric's ``compute`` or ``accumulate``.
"""
if self._unloaded:
raise RuntimeError("EvalWorker was unloaded; call reload() before evaluating.")
sample = dict(kwargs)
if self._pre_upload and self._any_needs_gpu:
sample["video"] = _to_device(sample.get("video"), self._device)
if "reference" in sample:
sample["reference"] = _to_device(sample["reference"], self._device)
results: dict[str, MetricResult] = {}
for name, m in self._metrics.items():
if m.is_set_metric:
m.accumulate(sample)
else:
results[name] = m.compute(sample)
return results
def set_metrics(self) -> dict[str, BaseMetric]:
"""Return ``{name: instance}`` for set metrics on this worker."""
return {n: m for n, m in self._metrics.items() if m.is_set_metric}
def reset_set_metrics(self) -> None:
"""Clear accumulator state on every set metric."""
for m in self._metrics.values():
if m.is_set_metric:
m.reset()
def release_cuda_memory(self) -> None:
"""Free CUDA caches without dropping models."""
clear_cache()
if torch.cuda.is_available():
with contextlib.suppress(Exception):
torch.cuda.ipc_collect()
def unload(self) -> None:
"""Drop metric refs so models become GC-able. Reverse with reload()."""
self._metrics = {}
self._unloaded = True
self.release_cuda_memory()
def reload(self) -> None:
"""Rebuild metrics dropped by :meth:`unload`."""
if self._unloaded:
self._load()
def _to_device(value: Any, device: str | torch.device) -> Any:
"""Move *value* to *device* if it's a tensor not already there."""
if value is None or not isinstance(value, torch.Tensor):
return value
target = torch.device(device)
if value.device == target:
return value
return value.to(target, non_blocking=True)