#!/usr/bin/env python2.7
#
# Copyright 2017 gRPC authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

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)