clerk @ 17c786e0f3f26481a635695160d516a7039a3bef

#!/usr/bin/env python3

"""Fail if any benchmark regressed beyond the threshold.

Reads benchstat CSV comparison (old vs new) from stdin. benchstat only

reports a numeric delta for statistically significant changes (p < 0.05);

noisy comparisons are marked "~" and ignored.

Only sec/op rows are judged; B/op and allocs/op deltas are informational

(deliberate tradeoffs like buffering input shift memory without slowing

down).

"""

import csv

import sys

THRESHOLD = 20.0  # percent slower

def delta_pct(s):

    s = s.strip()

    if not s or s == "~":

        return None

    sign = 1.0

    if s.startswith("+"):

        s = s[1:]

    elif s.startswith("-"):

        sign = -1.0

        s = s[1:]

    s = s.rstrip("%")

    if s in ("∞", "Inf", "inf", "+Inf"):

        return sign * float("inf")

    try:

        return sign * float(s)

    except ValueError:

        return None

def main():

    regressions = []

    unit = ""

    for row in csv.reader(sys.stdin):

        if row and row[0] == "":

            unit = row[1] if len(row) > 1 else ""

            continue

        if len(row) < 7 or row[0] in ("geomean",):

            continue

        if unit != "sec/op":

            continue

        d = delta_pct(row[5])  # vs base column

        if d is not None and d > THRESHOLD:

            regressions.append((row[0], d))

    if not regressions:

        print("no regressions beyond +%.0f%%" % THRESHOLD)

        return 0

    print("performance regressions beyond +%.0f%%:" % THRESHOLD)

    for name, d in sorted(regressions):

        if d == float("inf"):

            print("  %s: +∞ (new cost where none before)" % name)

        else:

            print("  %s: +%.1f%%" % (name, d))

    return 1

if __name__ == "__main__":

    sys.exit(main())