lsvbench/metrics.py

"""Generic metric helpers for benchmark tasks."""

from __future__ import annotations

import random
import statistics
from collections import Counter
from typing import Any, Callable, Iterable


def safe_div(num: float, denom: float) -> float | None:
    return num / denom if denom else None


def mean(values: Iterable[float | None]) -> float | None:
    clean = [value for value in values if value is not None]
    return sum(clean) / len(clean) if clean else None


def classification_scores(
    pairs: Iterable[tuple[Any, Any]],
    *,
    labels: Iterable[Any] | None = None,
    none_is_wrong: bool = True,
) -> dict[str, Any]:
    """Compute accuracy, balanced accuracy, F1, precision, recall, and confusion."""
    pair_list = list(pairs)
    if labels is None:
        label_values = sorted(
            {
                str(value)
                for target, pred in pair_list
                for value in (target, pred)
                if value is not None
            }
        )
    else:
        label_values = [str(label) for label in labels]
    total = len(pair_list)
    correct = sum(1 for target, pred in pair_list if pred is not None and str(target) == str(pred))
    target_total: Counter[str] = Counter()
    pred_total: Counter[str] = Counter()
    class_correct: Counter[str] = Counter()
    confusion: Counter[str] = Counter()
    for target, pred in pair_list:
        target_s = str(target)
        pred_s = "UNPARSED" if pred is None and none_is_wrong else str(pred)
        target_total[target_s] += 1
        pred_total[pred_s] += 1
        confusion[f"{target_s}->{pred_s}"] += 1
        if target_s == pred_s:
            class_correct[target_s] += 1

    recall: dict[str, float] = {}
    precision: dict[str, float] = {}
    f1: dict[str, float] = {}
    for label in label_values:
        recall[label] = class_correct[label] / target_total[label] if target_total[label] else 0.0
        precision[label] = class_correct[label] / pred_total[label] if pred_total[label] else 0.0
        denom = precision[label] + recall[label]
        f1[label] = 2 * precision[label] * recall[label] / denom if denom else 0.0
    return {
        "accuracy": correct / total if total else None,
        "balanced_accuracy": mean(recall.values()) if total and label_values else None,
        "macro_f1": mean(f1.values()) if total and label_values else None,
        "macro_precision": mean(precision.values()) if total and label_values else None,
        "macro_recall": mean(recall.values()) if total and label_values else None,
        "precision": precision,
        "recall": recall,
        "f1": f1,
        "confusion": dict(confusion),
        "target_counts": dict(target_total),
        "pred_counts": dict(pred_total),
    }


def parse_success_rate(rows: list[dict[str, Any]], field: str = "pred_parse_ok") -> float | None:
    if not rows:
        return None
    return sum(1 for row in rows if row.get(field)) / len(rows)


def metric_value(summary: dict[str, Any], metric: str) -> float | None:
    value = summary.get(metric)
    return value if isinstance(value, (int, float)) else None


def bootstrap_sem(
    rows: list[dict[str, Any]],
    metric: str,
    summarize_fn: Callable[[list[dict[str, Any]]], dict[str, Any]],
    *,
    iterations: int = 500,
    seed: int = 17,
) -> float | None:
    if not rows:
        return None
    rng = random.Random(f"{seed}:{metric}:{len(rows)}")
    values: list[float] = []
    for _ in range(iterations):
        sample = [rows[rng.randrange(len(rows))] for _ in rows]
        value = metric_value(summarize_fn(sample), metric)
        if value is not None:
            values.append(value)
    if not values:
        return None
    return statistics.stdev(values) if len(values) > 1 else 0.0