12bc53e031
-- c99f979ad34f155fbeeea69b88bdc7458d89a21c by Derek Mauro <dmauro@google.com>: Remove a floating point division by zero test. This isn't testing behavior related to the library, and MSVC warns about it in opt mode. PiperOrigin-RevId: 285220804 -- 68b015491f0dbf1ab547994673281abd1f34cd4b by Gennadiy Rozental <rogeeff@google.com>: This CL introduces following changes to the class FlagImpl: * We eliminate the CommandLineFlagLocks struct. Instead callback guard and callback function are combined into a single CallbackData struct, while primary data lock is stored separately. * CallbackData member of class FlagImpl is initially set to be nullptr and is only allocated and initialized when a flag's callback is being set. For most flags we do not pay for the extra space and extra absl::Mutex now. * Primary data guard is stored in data_guard_ data member. This is a properly aligned character buffer of necessary size. During initialization of the flag we construct absl::Mutex in this space using placement new call. * We now avoid extra value copy after successful attempt to parse value out of string. Instead we swap flag's current value with tentative value we just produced. PiperOrigin-RevId: 285132636 -- ed45d118fb818969eb13094cf7827c885dfc562c by Tom Manshreck <shreck@google.com>: Change null-term* (and nul-term*) to NUL-term* in comments PiperOrigin-RevId: 285036610 -- 729619017944db895ce8d6d29c1995aa2e5628a5 by Derek Mauro <dmauro@google.com>: Use the Posix implementation of thread identity on MinGW. Some versions of MinGW suffer from thread_local bugs. PiperOrigin-RevId: 285022920 -- 39a25493503c76885bc3254c28f66a251c5b5bb0 by Greg Falcon <gfalcon@google.com>: Implementation detail change. Add further ABSL_NAMESPACE_BEGIN and _END annotation macros to files in Abseil. PiperOrigin-RevId: 285012012 GitOrigin-RevId: c99f979ad34f155fbeeea69b88bdc7458d89a21c Change-Id: I4c85d3704e45d11a9ac50d562f39640a6adbedc1
89 lines
3 KiB
C++
89 lines
3 KiB
C++
// Copyright 2017 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef ABSL_RANDOM_INTERNAL_CHI_SQUARE_H_
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#define ABSL_RANDOM_INTERNAL_CHI_SQUARE_H_
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// The chi-square statistic.
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//
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// Useful for evaluating if `D` independent random variables are behaving as
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// expected, or if two distributions are similar. (`D` is the degrees of
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// freedom).
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//
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// Each bucket should have an expected count of 10 or more for the chi square to
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// be meaningful.
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#include <cassert>
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#include "absl/base/config.h"
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace random_internal {
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constexpr const char kChiSquared[] = "chi-squared";
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// Returns the measured chi square value, using a single expected value. This
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// assumes that the values in [begin, end) are uniformly distributed.
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template <typename Iterator>
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double ChiSquareWithExpected(Iterator begin, Iterator end, double expected) {
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// Compute the sum and the number of buckets.
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assert(expected >= 10); // require at least 10 samples per bucket.
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double chi_square = 0;
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for (auto it = begin; it != end; it++) {
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double d = static_cast<double>(*it) - expected;
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chi_square += d * d;
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}
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chi_square = chi_square / expected;
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return chi_square;
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}
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// Returns the measured chi square value, taking the actual value of each bucket
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// from the first set of iterators, and the expected value of each bucket from
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// the second set of iterators.
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template <typename Iterator, typename Expected>
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double ChiSquare(Iterator it, Iterator end, Expected eit, Expected eend) {
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double chi_square = 0;
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for (; it != end && eit != eend; ++it, ++eit) {
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if (*it > 0) {
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assert(*eit > 0);
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}
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double e = static_cast<double>(*eit);
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double d = static_cast<double>(*it - *eit);
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if (d != 0) {
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assert(e > 0);
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chi_square += (d * d) / e;
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}
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}
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assert(it == end && eit == eend);
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return chi_square;
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}
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// ======================================================================
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// The following methods can be used for an arbitrary significance level.
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//
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// Calculates critical chi-square values to produce the given p-value using a
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// bisection search for a value within epsilon, relying on the monotonicity of
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// ChiSquarePValue().
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double ChiSquareValue(int dof, double p);
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// Calculates the p-value (probability) of a given chi-square value.
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double ChiSquarePValue(double chi_square, int dof);
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} // namespace random_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_RANDOM_INTERNAL_CHI_SQUARE_H_
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