1 /*
2  * Copyright (C) 2017 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #ifndef ANDROID_FRAMEWORKS_ML_NN_COMMON_ACTIVATION_FUNCTOR_H
18 #define ANDROID_FRAMEWORKS_ML_NN_COMMON_ACTIVATION_FUNCTOR_H
19 
20 #include <android/log.h>
21 
22 #include <algorithm>
23 #include <cmath>
24 
25 enum ActivationFn {
26     kActivationNone = 0,
27     kActivationRelu,
28     kActivationRelu1,
29     kActivationRelu6,
30     kActivationTanh,
31     kActivationSignBit,
32     kActivationSigmoid,
33 };
34 
35 class ActivationFunctor {
36    public:
ActivationFunctor(ActivationFn act)37     explicit ActivationFunctor(ActivationFn act) : act_(act) {}
38 
operator()39     float operator()(float a) const {
40         switch (act_) {
41             case kActivationNone:
42                 return a;
43             case kActivationRelu:
44                 return a < 0.f ? 0.f : a;
45             case kActivationRelu6:
46                 return std::max(0.f, std::min(a, 6.f));
47             case kActivationTanh:
48                 return std::tanh(a);
49             case kActivationSigmoid:
50                 return 1.0f / (1.0f + std::exp(-a));
51             default:
52                 __android_log_print(ANDROID_LOG_ERROR, "NN API",
53                                     "Invalid enum value for activation function: 0x%0X", act_);
54                 abort();
55         }
56     }
57 
58    private:
59     ActivationFn act_;
60 };
61 
62 #endif  // ANDROID_FRAMEWORKS_ML_NN_COMMON_ACTIVATION_FUNCTOR_H
63