1 /* ----------------------------------------------------------------------
2 * Project: CMSIS DSP Library
3 * Title: arm_mean_q31.c
4 * Description: Mean value of a Q31 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 Q31 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 64-bit internal accumulator.
49 The input is represented in 1.31 format and is accumulated in a 64-bit
50 accumulator in 33.31 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 1.31 format.
54 */
55 #if defined(ARM_MATH_MVEI) && !defined(ARM_MATH_AUTOVECTORIZE)
arm_mean_q31(const q31_t * pSrc,uint32_t blockSize,q31_t * pResult)56 void arm_mean_q31(
57 const q31_t * pSrc,
58 uint32_t blockSize,
59 q31_t * pResult)
60 {
61 uint32_t blkCnt; /* loop counters */
62 q31x4_t vecSrc;
63 q63_t sum = 0LL;
64
65
66 /* Compute 4 outputs at a time */
67 blkCnt = blockSize >> 2U;
68 while (blkCnt > 0U)
69 {
70
71 vecSrc = vldrwq_s32(pSrc);
72 /*
73 * sum lanes
74 */
75 sum = vaddlvaq(sum, vecSrc);
76
77 blkCnt --;
78 pSrc += 4;
79 }
80
81 /* Tail */
82 blkCnt = blockSize & 0x3;
83
84 while (blkCnt > 0U)
85 {
86 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
87 sum += *pSrc++;
88 blkCnt --;
89 }
90
91 *pResult = arm_div_q63_to_q31(sum, blockSize);
92 }
93 #else
arm_mean_q31(const q31_t * pSrc,uint32_t blockSize,q31_t * pResult)94 void arm_mean_q31(
95 const q31_t * pSrc,
96 uint32_t blockSize,
97 q31_t * pResult)
98 {
99 uint32_t blkCnt; /* Loop counter */
100 q63_t sum = 0; /* Temporary result storage */
101
102 #if defined (ARM_MATH_LOOPUNROLL)
103
104 /* Loop unrolling: Compute 4 outputs at a time */
105 blkCnt = blockSize >> 2U;
106
107 while (blkCnt > 0U)
108 {
109 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
110 sum += *pSrc++;
111
112 sum += *pSrc++;
113
114 sum += *pSrc++;
115
116 sum += *pSrc++;
117
118 /* Decrement the loop counter */
119 blkCnt--;
120 }
121
122 /* Loop unrolling: Compute remaining outputs */
123 blkCnt = blockSize % 0x4U;
124
125 #else
126
127 /* Initialize blkCnt with number of samples */
128 blkCnt = blockSize;
129
130 #endif /* #if defined (ARM_MATH_LOOPUNROLL) */
131
132 while (blkCnt > 0U)
133 {
134 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
135 sum += *pSrc++;
136
137 /* Decrement loop counter */
138 blkCnt--;
139 }
140
141 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) / blockSize */
142 /* Store result to destination */
143 *pResult = (q31_t) (sum / blockSize);
144 }
145 #endif /* defined(ARM_MATH_MVEI) */
146
147 /**
148 @} end of mean group
149 */
150
