1// Copyright 2017 The TensorFlow Authors. All Rights Reserved.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14// =============================================================================
15#ifndef TENSORFLOW_CONTRIB_LIB_UTILS_RANDOM_H_
16#define TENSORFLOW_CONTRIB_LIB_UTILS_RANDOM_H_
17
18#include "tensorflow/core/lib/random/simple_philox.h"
19
20namespace tensorflow {
21namespace boosted_trees {
22namespace utils {
23
24// Generates a poisson distributed number with mean 1 for use in bootstrapping.
25inline int32 PoissonBootstrap(random::SimplePhilox* rng) {
26  // Knuth, special cased for lambda = 1.0 for efficiency.
27  static const float lbound = exp(-1.0f);
28  int32 n = 0;
29  for (float r = 1; r > lbound; r *= rng->RandFloat()) {
30    ++n;
31  }
32  return n - 1;
33}
34
35}  // namespace utils
36}  // namespace boosted_trees
37}  // namespace tensorflow
38
39#endif  // TENSORFLOW_CONTRIB_LIB_UTILS_RANDOM_H_
40