55 lines
1.7 KiB
Python
55 lines
1.7 KiB
Python
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# Copyright 2016 The Chromium Authors
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# Use of this source code is governed by a BSD-style license that can be
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# found in the LICENSE file.
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import copy
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import functools
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import math
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import random
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def RandomLowInteger(low, high, beta=31.0):
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"""Like random.randint, but heavily skewed toward the low end"""
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assert low <= high
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return low + int(math.floor(random.betavariate(1.0, beta) * (high - low)))
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def UniformExpoInteger(low, high, base=2):
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"""Returns base to a power uniformly distributed between low and high.
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This is useful for exploring large ranges of integers while ensuring that
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values of all different sizes are represented.
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"""
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return int(math.floor(math.pow(base, random.uniform(low, high))))
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def WeightedChoice(choices): # pylint: disable=inconsistent-return-statements
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"""Chooses an item given a sequence of (choice, weight) tuples"""
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total = sum(w for c, w in choices)
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r = random.uniform(0, total)
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upto = 0
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for c, w in choices:
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upto += w
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if upto >= r:
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return c
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assert False
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def Pipeline(*funcs):
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"""Given a number of single-argument functions, returns a single-argument
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function which computes their composition. Each of the functions are applied
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to the input in order from left to right, with the result of each function
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passed as the argument to the next function."""
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return reduce(lambda f, g: lambda x: g(f(x)), funcs)
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def DeepMemoize(obj):
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"""A memoizing decorator that returns deep copies of the function results."""
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cache = obj.cache = {}
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@functools.wraps(obj)
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def Memoize(*args):
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if args not in cache:
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cache[args] = copy.deepcopy(obj(*args))
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return copy.deepcopy(cache[args])
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return Memoize
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