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Python

# SPDX-License-Identifier: Apache-2.0
"""Metric policy for rolling performance baseline comparisons."""
from __future__ import annotations
from collections.abc import Mapping
from dataclasses import dataclass
from typing import Any
@dataclass(frozen=True)
class MetricPolicy:
key: str
label: str
precision: int
lower_is_better: bool
threshold_percent: float
threshold_absolute: float
gated: bool = True
@dataclass(frozen=True)
class MetricDelta:
absolute: float
percent: float
threshold_exceeded: bool
regressed: bool
DEFAULT_METRIC_POLICIES: tuple[MetricPolicy, ...] = (
MetricPolicy("latency", "Latency", 3, True, 0.08, 0.5),
MetricPolicy("throughput", "Throughput", 3, False, 0.08, 0.05),
MetricPolicy("memory", "Memory", 1, True, 0.05, 256.0),
MetricPolicy("text_encoder_time_s", "Text Enc", 3, True, 0.05, 0.25),
MetricPolicy("dit_time_s", "DiT", 3, True, 0.05, 0.25),
MetricPolicy("vae_decode_time_s", "VAE Decode", 3, True, 0.05, 0.25),
)
def _optional_float(value: Any) -> float | None:
if value is None or isinstance(value, bool):
return None
try:
return float(value)
except (TypeError, ValueError):
return None
def _optional_bool(value: Any) -> bool | None:
if isinstance(value, bool):
return value
if isinstance(value, str):
normalized = value.strip().lower()
if normalized in {"1", "true", "yes", "on"}:
return True
if normalized in {"0", "false", "no", "off"}:
return False
return None
def resolve_metric_policies(threshold_overrides: Mapping[str, Any] | None, ) -> tuple[MetricPolicy, ...]:
"""Return default metric policies with optional per-metric overrides."""
if not isinstance(threshold_overrides, Mapping):
threshold_overrides = {}
policies: list[MetricPolicy] = []
for base_policy in DEFAULT_METRIC_POLICIES:
raw_override = threshold_overrides.get(base_policy.key, {})
if not isinstance(raw_override, Mapping):
raw_override = {}
threshold_percent = _optional_float(raw_override.get("threshold_percent"))
threshold_absolute = _optional_float(raw_override.get("threshold_absolute"))
gated = _optional_bool(raw_override.get("gated"))
policies.append(
MetricPolicy(
key=base_policy.key,
label=base_policy.label,
precision=base_policy.precision,
lower_is_better=base_policy.lower_is_better,
threshold_percent=(base_policy.threshold_percent if threshold_percent is None else threshold_percent),
threshold_absolute=(base_policy.threshold_absolute
if threshold_absolute is None else threshold_absolute),
gated=base_policy.gated if gated is None else gated,
))
return tuple(policies)
def serialize_metric_thresholds(policies: tuple[MetricPolicy, ...], ) -> dict[str, dict[str, float | bool]]:
return {
policy.key: {
"threshold_percent": policy.threshold_percent,
"threshold_absolute": policy.threshold_absolute,
"gated": policy.gated,
}
for policy in policies
}
def regression_delta(
policy: MetricPolicy,
current: float,
baseline: float,
) -> MetricDelta | None:
if baseline <= 0:
return None
absolute_delta = current - baseline if policy.lower_is_better else baseline - current
percent_delta = absolute_delta / baseline
threshold_exceeded = (percent_delta > policy.threshold_percent and absolute_delta > policy.threshold_absolute)
return MetricDelta(
absolute=absolute_delta,
percent=percent_delta,
threshold_exceeded=threshold_exceeded,
regressed=policy.gated and threshold_exceeded,
)