56b1128c8f
Removed Rand(int low, int high) since that function outputs results that are non-random and/or outside the interval if low is negative. Added new Uniform(uint32_t, uint32_t) function to replace Rand(int low, int high). Changed various unit tests to use the new functions. BUG= Review URL: https://codereview.webrtc.org/1413053002 Cr-Commit-Position: refs/heads/master@{#10541}
73 lines
2.0 KiB
C++
73 lines
2.0 KiB
C++
/*
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* Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "webrtc/test/random.h"
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#include <math.h>
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#include "webrtc/base/checks.h"
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namespace webrtc {
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namespace test {
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Random::Random(uint32_t seed) : a_(0x531FDB97 ^ seed), b_(0x6420ECA8 + seed) {
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}
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uint32_t Random::Rand(uint32_t t) {
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// If b / 2^32 is uniform on [0,1), then b / 2^32 * (t+1) is uniform on
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// the interval [0,t+1), so the integer part is uniform on [0,t].
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uint64_t result = b_ * (static_cast<uint64_t>(t) + 1);
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result >>= 32;
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a_ ^= b_;
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b_ += a_;
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return result;
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}
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uint32_t Random::Rand(uint32_t low, uint32_t high) {
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RTC_DCHECK(low <= high);
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return Rand(high - low) + low;
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}
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template <>
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float Random::Rand<float>() {
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const double kScale = 1.0f / (static_cast<uint64_t>(1) << 32);
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double result = kScale * b_;
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a_ ^= b_;
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b_ += a_;
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return static_cast<float>(result);
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}
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template <>
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bool Random::Rand<bool>() {
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return Rand(0, 1) == 1;
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}
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int Random::Gaussian(int mean, int standard_deviation) {
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// Creating a Normal distribution variable from two independent uniform
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// variables based on the Box-Muller transform, which is defined on the
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// interval (0, 1], hence the mask+add below.
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const double kPi = 3.14159265358979323846;
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const double kScale = 1.0 / 0x80000000ul;
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double u1 = kScale * ((a_ & 0x7ffffffful) + 1);
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double u2 = kScale * ((b_ & 0x7ffffffful) + 1);
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a_ ^= b_;
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b_ += a_;
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return static_cast<int>(
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mean + standard_deviation * sqrt(-2 * log(u1)) * cos(2 * kPi * u2));
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}
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int Random::Exponential(float lambda) {
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float uniform = Rand<float>();
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return static_cast<int>(-log(uniform) / lambda);
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}
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} // namespace test
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} // namespace webrtc
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