wehub-resource-sync
119 lines
3.0 KiB
C++
119 lines
3.0 KiB
C++
/*!
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* Copyright (c) 2016-2026 Microsoft Corporation. All rights reserved.
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* Copyright (c) 2016-2026 The LightGBM developers. All rights reserved.
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* Licensed under the MIT License. See LICENSE file in the project root for license information.
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*/
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#ifndef LIGHTGBM_INCLUDE_LIGHTGBM_UTILS_RANDOM_H_
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#define LIGHTGBM_INCLUDE_LIGHTGBM_UTILS_RANDOM_H_
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#include <cstdint>
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#include <random>
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#include <set>
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#include <vector>
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namespace LightGBM {
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/*!
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* \brief A wrapper for random generator
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*/
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class Random {
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public:
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/*!
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* \brief Constructor, with random seed
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*/
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Random() {
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std::random_device rd;
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auto generator = std::mt19937(rd());
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std::uniform_int_distribution<int> distribution(0, x);
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x = distribution(generator);
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}
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/*!
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* \brief Constructor, with specific seed
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*/
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explicit Random(int seed) {
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x = seed;
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}
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/*!
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* \brief Generate random integer, int16 range. [0, 65536]
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* \param lower_bound lower bound
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* \param upper_bound upper bound
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* \return The random integer between [lower_bound, upper_bound)
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*/
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inline int NextShort(int lower_bound, int upper_bound) {
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return (RandInt16()) % (upper_bound - lower_bound) + lower_bound;
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}
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/*!
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* \brief Generate random integer, int32 range
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* \param lower_bound lower bound
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* \param upper_bound upper bound
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* \return The random integer between [lower_bound, upper_bound)
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*/
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inline int NextInt(int lower_bound, int upper_bound) {
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return (RandInt32()) % (upper_bound - lower_bound) + lower_bound;
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}
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/*!
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* \brief Generate random float data
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* \return The random float between [0.0, 1.0)
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*/
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inline float NextFloat() {
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// get random float in [0,1)
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return static_cast<float>(RandInt16()) / (32768.0f);
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}
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/*!
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* \brief Sample K data from {0,1,...,N-1}
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* \param N
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* \param K
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* \return K Ordered sampled data from {0,1,...,N-1}
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*/
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inline std::vector<int> Sample(int N, int K) {
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std::vector<int> ret;
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ret.reserve(K);
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if (K > N || K <= 0) {
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return ret;
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} else if (K == N) {
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for (int i = 0; i < N; ++i) {
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ret.push_back(i);
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}
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} else if (K > 1 && K > (N / std::log2(K))) {
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for (int i = 0; i < N; ++i) {
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double prob = (K - ret.size()) / static_cast<double>(N - i);
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if (NextFloat() < prob) {
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ret.push_back(i);
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}
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}
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} else {
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std::set<int> sample_set;
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for (int r = N - K; r < N; ++r) {
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int v = NextInt(0, r + 1);
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if (!sample_set.insert(v).second) {
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sample_set.insert(r);
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}
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}
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for (auto iter = sample_set.begin(); iter != sample_set.end(); ++iter) {
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ret.push_back(*iter);
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}
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}
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return ret;
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}
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private:
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inline int RandInt16() {
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x = (214013 * x + 2531011);
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return static_cast<int>((x >> 16) & 0x7FFF);
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}
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inline int RandInt32() {
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x = (214013 * x + 2531011);
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return static_cast<int>(x & 0x7FFFFFFF);
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}
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unsigned int x = 123456789;
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};
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} // namespace LightGBM
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#endif // LIGHTGBM_INCLUDE_LIGHTGBM_UTILS_RANDOM_H_
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