1 /*
2 * Copyright (C) 2010-2020 Arm Limited or its affiliates. All rights reserved.
3 *
4 * SPDX-License-Identifier: Apache-2.0
5 *
6 * Licensed under the Apache License, Version 2.0 (the License); you may
7 * not use this file except in compliance with the License.
8 * You may obtain a copy of the License at
9 *
10 * www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
14 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
17 */
18
19 /* ----------------------------------------------------------------------
20 * Project: CMSIS NN Library
21 * Title: arm_nn_activations_q15.c
22 * Description: Q15 neural network activation function using direct table look-up
23 *
24 * $Date: 09. October 2020
25 * $Revision: V.1.0.1
26 *
27 * Target Processor: Cortex-M cores
28 *
29 * -------------------------------------------------------------------- */
30
31 #include "arm_nn_tables.h"
32 #include "arm_nnfunctions.h"
33
34 /**
35 * @ingroup groupNN
36 */
37
38 /**
39 * @addtogroup Acti
40 * @{
41 */
42
43 /**
44 * @brief neural network activation function using direct table look-up
45 *
46 * @note Refer header file for details.
47 *
48 */
49
arm_nn_activations_direct_q15(q15_t * data,uint16_t size,uint16_t int_width,arm_nn_activation_type type)50 void arm_nn_activations_direct_q15(q15_t *data, uint16_t size, uint16_t int_width, arm_nn_activation_type type)
51 {
52 uint16_t i = size;
53 q15_t *pIn = data;
54 q15_t *pOut = data;
55 uint16_t shift_size = 8 + 3 - int_width;
56 uint32_t bit_mask = 0x7FF >> int_width;
57 uint32_t full_frac = bit_mask + 1;
58 const q15_t *lookup_table;
59
60 switch (type)
61 {
62 case ARM_SIGMOID:
63 lookup_table = sigmoidTable_q15;
64 break;
65 case ARM_TANH:
66 default:
67 lookup_table = tanhTable_q15;
68 break;
69 }
70
71 while (i)
72 {
73 q15_t out;
74 q15_t in = *pIn++;
75 q15_t frac = (uint32_t)in & bit_mask;
76 q15_t value = lookup_table[(uint8_t)(in >> shift_size)];
77 if ((in >> shift_size) != 0x7f)
78 {
79 q15_t value2 = lookup_table[(uint8_t)(1 + ((uint8_t)(in >> shift_size)))];
80 /* doing the interpolation here for better accuracy */
81 out = ((q31_t)(full_frac - frac) * value + (q31_t)value2 * frac) >> shift_size;
82 }
83 else
84 {
85 /* the largest positive value does not have a right side for linear interpolation */
86 out = value;
87 }
88
89 *pOut++ = out;
90 i--;
91 }
92 }
93
94 /**
95 * @} end of Acti group
96 */
97
