1 /* Copyright 2022 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
16 // Common utilities for random shuffling.
17
18 #ifndef TENSORFLOW_CORE_KERNELS_RANDOM_SHUFFLE_COMMON_H_
19 #define TENSORFLOW_CORE_KERNELS_RANDOM_SHUFFLE_COMMON_H_
20
21 #include <algorithm>
22 #include <functional>
23
24 #include "tensorflow/core/framework/op_kernel.h"
25 #include "tensorflow/core/framework/tensor_util.h"
26 #include "tensorflow/core/lib/random/philox_random.h"
27 #include "tensorflow/core/lib/random/random_distributions.h"
28
29 namespace tensorflow {
30
31 // TODO(irving): If performance is critical, generate output directly instead
32 // of an in-place shuffle using a pseudorandom permutation like
33 //
34 // https://github.com/otherlab/geode/blob/master/geode/random/permute.cpp
35 //
36 // This is probably also the right thing if we want a GPU version of shuffling.
37
38 // We use our own version of std::random_shuffle to guarantee that exactly
39 // size - 1 samples are used.
40 template <class Iter, class Random>
ShuffleRange(Iter first,Iter last,Random & uniform)41 static inline void ShuffleRange(Iter first, Iter last, Random& uniform) {
42 if (first == last) return;
43 const auto stop = last - 1;
44 for (auto i = first; i != stop; ++i) {
45 using std::iter_swap;
46 iter_swap(i, i + uniform(last - i));
47 }
48 }
49
50 template <class IntT, class InT, class OutT, class Random>
IndexedShuffle(const int64_t size,const InT & input_mat,OutT output_mat,Random & uniform)51 static void IndexedShuffle(const int64_t size, const InT& input_mat,
52 OutT output_mat, Random& uniform) {
53 std::vector<IntT> permutation(size);
54 for (IntT i = 0; i < size; i++) {
55 permutation[i] = i;
56 }
57 ShuffleRange(permutation.begin(), permutation.end(), uniform);
58 for (IntT i = 0; i < size; i++) {
59 output_mat.template chip<0>(i) = input_mat.template chip<0>(permutation[i]);
60 }
61 }
62
63 template <typename T>
RandomShuffle(OpKernelContext * context,const Tensor & input,int output_idx,std::function<random::PhiloxRandom (int64_t)> get_rng)64 Status RandomShuffle(OpKernelContext* context, const Tensor& input,
65 int output_idx,
66 std::function<random::PhiloxRandom(int64_t)> get_rng) {
67 if (input.NumElements() <= 1 || input.dim_size(0) <= 1) {
68 // No shuffling is required, so copy input directly to output
69 context->set_output(output_idx, input);
70 } else {
71 // Reserve enough random samples for shuffling
72 const int64_t size = input.dim_size(0);
73 const int64_t samples = size - 1;
74 auto rng = get_rng(samples);
75 random::SingleSampleAdapter<random::PhiloxRandom> single(&rng);
76 const auto uniform = [&single](uint32 n) { return single() % n; };
77
78 if (input.dims() == 1) {
79 // For 1D data, copy and then shuffle in place
80 context->set_output(output_idx, tensor::DeepCopy(input));
81 auto vec = context->mutable_output(output_idx)->vec<T>();
82 ShuffleRange(vec.data(), vec.data() + size, uniform);
83 } else {
84 // For >= 2D, shuffle indices and then copy across
85 Tensor* output = nullptr;
86 TF_RETURN_IF_ERROR(
87 context->allocate_output(output_idx, input.shape(), &output));
88 const auto input_mat = input.flat_outer_dims<T>();
89 auto output_mat = output->flat_outer_dims<T>();
90 if (size < kint32max) {
91 IndexedShuffle<int32>(size, input_mat, output_mat, uniform);
92 } else {
93 IndexedShuffle<int64_t>(size, input_mat, output_mat, uniform);
94 }
95 }
96 }
97 return OkStatus();
98 }
99
100 } // namespace tensorflow
101
102 #endif // TENSORFLOW_CORE_KERNELS_RANDOM_SHUFFLE_COMMON_H_
103