#!/usr/bin/env python

import argparse
import sys

have_scipy = True
try:
    import scipy.stats
except:
    have_scipy = False

SIGNIFICANCE_THRESHOLD = 0.0001

parser = argparse.ArgumentParser(
    formatter_class=argparse.RawDescriptionHelpFormatter,
    description='Compare performance of two runs from nanobench.')
parser.add_argument('--use_means', action='store_true', default=False,
                    help='Use means to calculate performance ratios.')
parser.add_argument('baseline', help='Baseline file.')
parser.add_argument('experiment', help='Experiment file.')
args = parser.parse_args()

a,b = {},{}
for (path, d) in [(args.baseline, a), (args.experiment, b)]:
    for line in open(path):
        try:
            tokens = line.split()
            if tokens[0] != "Samples:":
                continue
            samples  = tokens[1:-1]
            label    = tokens[-1]
            d[label] = map(float, samples)
        except:
            pass

common = set(a.keys()).intersection(b.keys())

def mean(xs):
    return sum(xs) / len(xs)

ps = []
for key in common:
    p, asem, bsem = 0, 0, 0
    m = mean if args.use_means else min
    am, bm = m(a[key]), m(b[key])
    if have_scipy:
        _, p = scipy.stats.mannwhitneyu(a[key], b[key])
        asem, bsem = scipy.stats.sem(a[key]), scipy.stats.sem(b[key])
    ps.append((bm/am, p, key, am, bm, asem, bsem))
ps.sort(reverse=True)

def humanize(ns):
    for threshold, suffix in [(1e9, 's'), (1e6, 'ms'), (1e3, 'us'), (1e0, 'ns')]:
        if ns > threshold:
            return "%.3g%s" % (ns/threshold, suffix)

maxlen = max(map(len, common))

# We print only signficant changes in benchmark timing distribution.
bonferroni = SIGNIFICANCE_THRESHOLD / len(ps)  # Adjust for the fact we've run multiple tests.
for ratio, p, key, am, bm, asem, bsem in ps:
    if p < bonferroni:
        str_ratio = ('%.2gx' if ratio < 1 else '%.3gx') % ratio
        if args.use_means:
            print '%*s\t%6s(%6s) -> %6s(%6s)\t%s' % (maxlen, key, humanize(am), humanize(asem),
                                                     humanize(bm), humanize(bsem), str_ratio)
        else:
            print '%*s\t%6s -> %6s\t%s' % (maxlen, key, humanize(am), humanize(bm), str_ratio)