1 /* Copyright 2015 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 // See docs in ../ops/random_ops.cc.
17
18 #include <vector>
19 #include "tensorflow/core/framework/op_kernel.h"
20 #include "tensorflow/core/framework/register_types.h"
21 #include "tensorflow/core/framework/tensor.h"
22 #include "tensorflow/core/framework/tensor_shape.h"
23 #include "tensorflow/core/framework/tensor_util.h"
24 #include "tensorflow/core/lib/random/random_distributions.h"
25 #include "tensorflow/core/platform/logging.h"
26 #include "tensorflow/core/util/guarded_philox_random.h"
27
28 namespace tensorflow {
29
30 // TODO(irving): If performance is critical, generate output directly instead
31 // of an in-place shuffle using a pseudorandom permutation like
32 //
33 // https://github.com/otherlab/geode/blob/master/geode/random/permute.cpp
34 //
35 // This is probably also the right thing if we want a GPU version of shuffling.
36
37 // We use our own version of std::random_shuffle to guarantee that exactly
38 // size - 1 samples are used.
39 template <class Iter, class Random>
RandomShuffle(Iter first,Iter last,Random & uniform)40 static inline void RandomShuffle(Iter first, Iter last, Random& uniform) {
41 if (first == last) return;
42 const auto stop = last - 1;
43 for (auto i = first; i != stop; ++i) {
44 using std::iter_swap;
45 iter_swap(i, i + uniform(last - i));
46 }
47 }
48
49 template <class IntT, class InT, class OutT, class Random>
IndexedShuffle(const int64 size,const InT & input_mat,OutT output_mat,Random & uniform)50 static void IndexedShuffle(const int64 size, const InT& input_mat,
51 OutT output_mat, Random& uniform) {
52 std::vector<IntT> permutation(size);
53 for (IntT i = 0; i < size; i++) {
54 permutation[i] = i;
55 }
56 RandomShuffle(permutation.begin(), permutation.end(), uniform);
57 for (IntT i = 0; i < size; i++) {
58 output_mat.template chip<0>(i) = input_mat.template chip<0>(permutation[i]);
59 }
60 }
61
62 template <typename T>
63 class RandomShuffleOp : public OpKernel {
64 public:
RandomShuffleOp(OpKernelConstruction * context)65 explicit RandomShuffleOp(OpKernelConstruction* context) : OpKernel(context) {
66 OP_REQUIRES_OK(context, generator_.Init(context));
67 }
68
Compute(OpKernelContext * context)69 void Compute(OpKernelContext* context) override {
70 const Tensor& input = context->input(0);
71
72 if (input.NumElements() <= 1 || input.dim_size(0) <= 1) {
73 // No shuffling is required, so copy input directly to output
74 context->set_output(0, input);
75 } else {
76 // Reserve enough random samples for shuffling
77 const int64 size = input.dim_size(0);
78 const int64 samples = size - 1;
79 auto local_gen = generator_.ReserveSamples32(samples);
80 random::SingleSampleAdapter<random::PhiloxRandom> single(&local_gen);
81 const auto uniform = [&single](uint32 n) { return single() % n; };
82
83 if (input.dims() == 1) {
84 // For 1D data, copy and then shuffle in place
85 context->set_output(0, tensor::DeepCopy(input));
86 auto vec = context->mutable_output(0)->vec<T>();
87 RandomShuffle(vec.data(), vec.data() + size, uniform);
88 } else {
89 // For >= 2D, shuffle indices and then copy across
90 Tensor* output = nullptr;
91 OP_REQUIRES_OK(context,
92 context->allocate_output(0, input.shape(), &output));
93 const auto input_mat = input.flat_outer_dims<T>();
94 auto output_mat = output->flat_outer_dims<T>();
95 if (size < kint32max) {
96 IndexedShuffle<int32>(size, input_mat, output_mat, uniform);
97 } else {
98 IndexedShuffle<int64>(size, input_mat, output_mat, uniform);
99 }
100 }
101 }
102 }
103
104 private:
105 GuardedPhiloxRandom generator_;
106 };
107
108 #define REGISTER(T) \
109 REGISTER_KERNEL_BUILDER( \
110 Name("RandomShuffle").Device(DEVICE_CPU).TypeConstraint<T>("T"), \
111 RandomShuffleOp<T>);
112 TF_CALL_ALL_TYPES(REGISTER)
113
114 } // namespace tensorflow
115