1 /* ----------------------------------------------------------------------
2 * Project: CMSIS DSP Library
3 * Title: arm_var_f64.c
4 * Description: Variance of the elements of a floating-point vector
5 *
6 * $Date: 13 September 2021
7 * $Revision: V1.10.0
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 variance
37 @{
38 */
39
40 /**
41 @brief Variance of the elements of a floating-point vector.
42 @param[in] pSrc points to the input vector
43 @param[in] blockSize number of samples in input vector
44 @param[out] pResult variance value returned here
45 */
arm_var_f64(const float64_t * pSrc,uint32_t blockSize,float64_t * pResult)46 ARM_DSP_ATTRIBUTE void arm_var_f64(
47 const float64_t * pSrc,
48 uint32_t blockSize,
49 float64_t * pResult)
50 {
51
52 uint32_t blkCnt; /* Loop counter */
53 float64_t fSum = 0.;
54 float64_t fMean, fValue;
55 const float64_t * pInput = pSrc;
56
57 if (blockSize <= 1U)
58 {
59 *pResult = 0;
60 return;
61 }
62 arm_mean_f64(pInput, blockSize, &fMean);
63 #if defined(ARM_MATH_NEON) && defined(__aarch64__)
64 float64x2_t fValueV ,fsumV , pInputV , fMeanV;
65 fsumV = vdupq_n_f64(0.0);
66 fMeanV = vdupq_n_f64(fMean);
67 blkCnt = blockSize >> 1U;
68
69 while(blkCnt > 0U)
70 {
71 pInputV = vld1q_f64(pInput);
72 fValueV = vsubq_f64(pInputV, fMeanV);
73 fsumV = vmlaq_f64(fsumV, fValueV, fValueV);
74 pInput += 2 ;
75 blkCnt--;
76 }
77 fSum = vaddvq_f64(fsumV);
78
79 blkCnt = blockSize & 1 ;
80
81 #else
82 /* Initialize blkCnt with number of samples */
83 blkCnt = blockSize;
84 #endif
85 while (blkCnt > 0U)
86 {
87 fValue = *pInput++ - fMean;
88 fSum += fValue * fValue;
89
90 /* Decrement loop counter */
91 blkCnt--;
92 }
93
94 /* Variance */
95 *pResult = fSum / (float64_t)(blockSize - 1.);
96 }
97
98 /**
99 @} end of variance group
100 */
101
