1 /* ----------------------------------------------------------------------
2 * Project: CMSIS DSP Library
3 * Title: arm_mean_q7.c
4 * Description: Mean value of a Q7 vector
5 *
6 * $Date: 23 April 2021
7 * $Revision: V1.9.0
8 *
9 * Target Processor: Cortex-M and Cortex-A cores
10 * -------------------------------------------------------------------- */
11 /*
12 * Copyright (C) 2010-2021 ARM Limited or its affiliates. All rights reserved.
13 *
14 * SPDX-License-Identifier: Apache-2.0
15 *
16 * Licensed under the Apache License, Version 2.0 (the License); you may
17 * not use this file except in compliance with the License.
18 * You may obtain a copy of the License at
19 *
20 * www.apache.org/licenses/LICENSE-2.0
21 *
22 * Unless required by applicable law or agreed to in writing, software
23 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
24 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
25 * See the License for the specific language governing permissions and
26 * limitations under the License.
27 */
28
29 #include "dsp/statistics_functions.h"
30
31 /**
32 @ingroup groupStats
33 */
34
35 /**
36 @addtogroup mean
37 @{
38 */
39
40 /**
41 @brief Mean value of a Q7 vector.
42 @param[in] pSrc points to the input vector
43 @param[in] blockSize number of samples in input vector
44 @param[out] pResult mean value returned here
45 @return none
46
47 @par Scaling and Overflow Behavior
48 The function is implemented using a 32-bit internal accumulator.
49 The input is represented in 1.7 format and is accumulated in a 32-bit
50 accumulator in 25.7 format.
51 There is no risk of internal overflow with this approach, and the
52 full precision of intermediate result is preserved.
53 Finally, the accumulator is truncated to yield a result of 1.7 format.
54 */
55
56 #if defined(ARM_MATH_MVEI) && !defined(ARM_MATH_AUTOVECTORIZE)
57
arm_mean_q7(const q7_t * pSrc,uint32_t blockSize,q7_t * pResult)58 void arm_mean_q7(
59 const q7_t * pSrc,
60 uint32_t blockSize,
61 q7_t * pResult)
62 {
63 uint32_t blkCnt; /* loop counters */
64 q7x16_t vecSrc;
65 q31_t sum = 0L;
66
67
68 blkCnt = blockSize >> 4;
69 while (blkCnt > 0U)
70 {
71 vecSrc = vldrbq_s8(pSrc);
72 /*
73 * sum lanes
74 */
75 sum = vaddvaq(sum, vecSrc);
76
77 blkCnt--;
78 pSrc += 16;
79 }
80
81 blkCnt = blockSize & 0xF;
82 while (blkCnt > 0U)
83 {
84 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
85 sum += *pSrc++;
86
87 /* Decrement loop counter */
88 blkCnt--;
89 }
90
91 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) / blockSize */
92 /* Store the result to the destination */
93 *pResult = (q7_t) (sum / (int32_t) blockSize);
94 }
95 #else
arm_mean_q7(const q7_t * pSrc,uint32_t blockSize,q7_t * pResult)96 void arm_mean_q7(
97 const q7_t * pSrc,
98 uint32_t blockSize,
99 q7_t * pResult)
100 {
101 uint32_t blkCnt; /* Loop counter */
102 q31_t sum = 0; /* Temporary result storage */
103
104 #if defined (ARM_MATH_LOOPUNROLL)
105 q31_t in;
106 #endif
107
108 #if defined (ARM_MATH_LOOPUNROLL)
109
110 /* Loop unrolling: Compute 4 outputs at a time */
111 blkCnt = blockSize >> 2U;
112
113 while (blkCnt > 0U)
114 {
115 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
116 in = read_q7x4_ia ((q7_t **) &pSrc);
117 sum += ((in << 24U) >> 24U);
118 sum += ((in << 16U) >> 24U);
119 sum += ((in << 8U) >> 24U);
120 sum += (in >> 24U);
121
122 /* Decrement the loop counter */
123 blkCnt--;
124 }
125
126 /* Loop unrolling: Compute remaining outputs */
127 blkCnt = blockSize % 0x4U;
128
129 #else
130
131 /* Initialize blkCnt with number of samples */
132 blkCnt = blockSize;
133
134 #endif /* #if defined (ARM_MATH_LOOPUNROLL) */
135
136 while (blkCnt > 0U)
137 {
138 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
139 sum += *pSrc++;
140
141 /* Decrement loop counter */
142 blkCnt--;
143 }
144
145 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) / blockSize */
146 /* Store result to destination */
147 *pResult = (q7_t) (sum / (int32_t) blockSize);
148 }
149 #endif /* defined(ARM_MATH_MVEI) */
150
151 /**
152 @} end of mean group
153 */
154