Function compareBenchmarkRuns

scripts/compare-release-benchmarks.ts:182–268

(
  base: BenchmarkRunResult,
  head: BenchmarkRunResult,
)

/** Compare two benchmark snapshots and mark only material regressions as failures. */
export function compareBenchmarkRuns(
  base: BenchmarkRunResult,
  head: BenchmarkRunResult,
): BenchmarkComparisonResult {
  const baseByName = new Map(base.results.map((result) => [result.name, result]));
  const headByName = new Map(head.results.map((result) => [result.name, result]));
  const acceptedRegressionNames = new Set(
    (head.acceptedRegressions ?? []).map((entry) => entry.name),
  );
  const names = [...new Set([...baseByName.keys(), ...headByName.keys()])].sort();
  const rows: BenchmarkComparisonRow[] = names.map((name) => {
    const baseResult = baseByName.get(name);
    const headResult = headByName.get(name);
    const resultForMetadata = headResult ?? baseResult;
    const threshold = comparableThreshold(baseResult, headResult);

    if (!baseResult && headResult) {
      return {
        name,
        unit: headResult.unit,
        baseMedian: 0,
        headMedian: headResult.median,
        absoluteDelta: headResult.median,
        relativeDelta: Number.POSITIVE_INFINITY,
        threshold,
        status: headResult.comparable ? "missing-base" : "informational",
        source: headResult.source,
      };
    }

    if (baseResult && !headResult) {
      return {
        name,
        unit: baseResult.unit,
        baseMedian: baseResult.median,
        headMedian: 0,
        absoluteDelta: -baseResult.median,
        relativeDelta: -1,
        threshold,
        status: baseResult.comparable ? "missing-head" : "informational",
        source: baseResult.source,
      };
    }

    const checkedBase = baseResult!;
    const checkedHead = headResult!;
    const absoluteDelta = checkedHead.median - checkedBase.median;
    const row: BenchmarkComparisonRow = {
      name,
      unit: checkedHead.unit,
      baseMedian: checkedBase.median,
      headMedian: checkedHead.median,
      absoluteDelta,
      relativeDelta: relativeDelta(checkedBase.median, checkedHead.median),
      threshold,
      status: "informational",
      source: resultForMetadata!.source,
    };