1 /*
2 * Copyright (C) 2010-2018 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: 17. January 2018
25 * $Revision: V.1.0.0
26 *
27 * Target Processor: Cortex-M cores
28 *
29 * -------------------------------------------------------------------- */
30
31 #include "arm_math.h"
32 #include "arm_common_tables.h"
33 #include "arm_nnfunctions.h"
34
35 /**
36 * @ingroup groupNN
37 */
38
39 /**
40 * @addtogroup Acti
41 * @{
42 */
43
44 /**
45 * @brief Q15 neural network activation function using direct table look-up
46 * @param[in,out] data pointer to input
47 * @param[in] size number of elements
48 * @param[in] int_width bit-width of the integer part, assume to be smaller than 3
49 * @param[in] type type of activation functions
50 * @return none.
51 *
52 * @details
53 *
54 * This is the direct table look-up approach.
55 *
56 * Assume here the integer part of the fixed-point is <= 3.
57 * More than 3 just not making much sense, makes no difference with
58 * saturation followed by any of these activation functions.
59 */
60
arm_nn_activations_direct_q15(q15_t * data,uint16_t size,uint16_t int_width,arm_nn_activation_type type)61 void arm_nn_activations_direct_q15(q15_t * data, uint16_t size, uint16_t int_width, arm_nn_activation_type type)
62 {
63 uint16_t i = size;
64 q15_t *pIn = data;
65 q15_t *pOut = data;
66 uint16_t shift_size = 8 + 3 - int_width;
67 uint32_t bit_mask = 0x7FF >> int_width;
68 uint32_t full_frac = bit_mask + 1;
69 const q15_t *lookup_table;
70
71 switch (type)
72 {
73 case ARM_SIGMOID:
74 lookup_table = sigmoidTable_q15;
75 break;
76 case ARM_TANH:
77 default:
78 lookup_table = tanhTable_q15;
79 break;
80 }
81
82 while (i)
83 {
84 q15_t out;
85 q15_t in = *pIn++;
86 q15_t frac = (uint32_t) in & bit_mask;
87 q15_t value = lookup_table[__USAT(in >> shift_size, 8)];
88 q15_t value2 = lookup_table[__USAT(1 + (in >> shift_size), 8)];
89
90 /* doing the interpolation here for better accuracy */
91 out = ((q31_t) (full_frac - frac) * value + (q31_t) value2 * frac) >> shift_size;
92
93 *pOut++ = out;
94 i--;
95 }
96
97 }
98
99 /**
100 * @} end of Acti group
101 */
102