#!/usr/bin/env python2.7
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""" The math behind the diff functionality """

from scipy import stats
import math

_THRESHOLD = 1e-10


def scale(a, mul):
    return [x * mul for x in a]


def cmp(a, b):
    return stats.ttest_ind(a, b)


def speedup(new, old):
    if (len(set(new))) == 1 and new == old: return 0
    s0, p0 = cmp(new, old)
    if math.isnan(p0): return 0
    if s0 == 0: return 0
    if p0 > _THRESHOLD: return 0
    if s0 < 0:
        pct = 1
        while pct < 101:
            sp, pp = cmp(new, scale(old, 1 - pct / 100.0))
            if sp > 0: break
            if pp > _THRESHOLD: break
            pct += 1
        return -(pct - 1)
    else:
        pct = 1
        while pct < 100000:
            sp, pp = cmp(new, scale(old, 1 + pct / 100.0))
            if sp < 0: break
            if pp > _THRESHOLD: break
            pct += 1
        return pct - 1


if __name__ == "__main__":
    new = [1.0, 1.0, 1.0, 1.0]
    old = [2.0, 2.0, 2.0, 2.0]
    print speedup(new, old)
    print speedup(old, new)