1/* Copyright 2015 The TensorFlow Authors. All Rights Reserved.
2
3Licensed under the Apache License, Version 2.0 (the "License");
4you may not use this file except in compliance with the License.
5You may obtain a copy of the License at
6
7 http://www.apache.org/licenses/LICENSE-2.0
8
9Unless required by applicable law or agreed to in writing, software
10distributed under the License is distributed on an "AS IS" BASIS,
11WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12See the License for the specific language governing permissions and
13limitations under the License.
14==============================================================================*/
15
16#ifndef TENSORFLOW_CORE_KERNELS_STRING_TO_HASH_BUCKET_FAST_OP_H_
17#define TENSORFLOW_CORE_KERNELS_STRING_TO_HASH_BUCKET_FAST_OP_H_
18
19#include <string>
20
21#include "tensorflow/core/framework/op_kernel.h"
22#include "tensorflow/core/framework/tensor.h"
23#include "tensorflow/core/lib/core/errors.h"
24#include "tensorflow/core/lib/core/status.h"
25#include "tensorflow/core/platform/macros.h"
26
27namespace tensorflow {
28
29template <uint64 hash(StringPiece)>
30class StringToHashBucketOp : public OpKernel {
31 public:
32 explicit StringToHashBucketOp(OpKernelConstruction* ctx) : OpKernel(ctx) {
33 OP_REQUIRES_OK(ctx, ctx->GetAttr("num_buckets", &num_buckets_));
34 }
35
36 void Compute(OpKernelContext* context) override {
37 const Tensor* input_tensor;
38 OP_REQUIRES_OK(context, context->input("input", &input_tensor));
39 const auto& input_flat = input_tensor->flat<tstring>();
40
41 Tensor* output_tensor = nullptr;
42 OP_REQUIRES_OK(context,
43 context->allocate_output("output", input_tensor->shape(),
44 &output_tensor));
45 auto output_flat = output_tensor->flat<int64_t>();
46
47 typedef decltype(input_flat.size()) Index;
48 for (Index i = 0; i < input_flat.size(); ++i) {
49 const uint64 input_hash = hash(input_flat(i));
50 const uint64 bucket_id = input_hash % num_buckets_;
51 // The number of buckets is always in the positive range of int64 so is
52 // the resulting bucket_id. Casting the bucket_id from uint64 to int64 is
53 // safe.
54 output_flat(i) = static_cast<int64_t>(bucket_id);
55 }
56 }
57
58 private:
59 int64_t num_buckets_;
60
61 TF_DISALLOW_COPY_AND_ASSIGN(StringToHashBucketOp);
62};
63
64} // namespace tensorflow
65
66#endif // TENSORFLOW_CORE_KERNELS_STRING_TO_HASH_BUCKET_FAST_OP_H_
67