|
2
|
1 /* ----------------------------------------------------------------------
|
|
|
2 * Copyright (C) 2010-2014 ARM Limited. All rights reserved.
|
|
|
3 *
|
|
|
4 * $Date: 19. March 2015
|
|
|
5 * $Revision: V.1.4.5
|
|
|
6 *
|
|
|
7 * Project: CMSIS DSP Library
|
|
|
8 * Title: arm_std_f32.c
|
|
|
9 *
|
|
|
10 * Description: Standard deviation of the elements of a floating-point vector.
|
|
|
11 *
|
|
|
12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
|
|
|
13 *
|
|
|
14 * Redistribution and use in source and binary forms, with or without
|
|
|
15 * modification, are permitted provided that the following conditions
|
|
|
16 * are met:
|
|
|
17 * - Redistributions of source code must retain the above copyright
|
|
|
18 * notice, this list of conditions and the following disclaimer.
|
|
|
19 * - Redistributions in binary form must reproduce the above copyright
|
|
|
20 * notice, this list of conditions and the following disclaimer in
|
|
|
21 * the documentation and/or other materials provided with the
|
|
|
22 * distribution.
|
|
|
23 * - Neither the name of ARM LIMITED nor the names of its contributors
|
|
|
24 * may be used to endorse or promote products derived from this
|
|
|
25 * software without specific prior written permission.
|
|
|
26 *
|
|
|
27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
|
|
28 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
|
|
29 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
|
|
|
30 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
|
|
|
31 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
|
32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
|
|
|
33 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
|
|
|
34 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
|
|
|
35 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
|
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
|
|
|
37 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
|
38 * POSSIBILITY OF SUCH DAMAGE.
|
|
|
39 * ---------------------------------------------------------------------------- */
|
|
|
40
|
|
|
41 #include "arm_math.h"
|
|
|
42
|
|
|
43 /**
|
|
|
44 * @ingroup groupStats
|
|
|
45 */
|
|
|
46
|
|
|
47 /**
|
|
|
48 * @defgroup STD Standard deviation
|
|
|
49 *
|
|
|
50 * Calculates the standard deviation of the elements in the input vector.
|
|
|
51 * The underlying algorithm is used:
|
|
|
52 *
|
|
|
53 * <pre>
|
|
|
54 * Result = sqrt((sumOfSquares - sum<sup>2</sup> / blockSize) / (blockSize - 1))
|
|
|
55 *
|
|
|
56 * where, sumOfSquares = pSrc[0] * pSrc[0] + pSrc[1] * pSrc[1] + ... + pSrc[blockSize-1] * pSrc[blockSize-1]
|
|
|
57 *
|
|
|
58 * sum = pSrc[0] + pSrc[1] + pSrc[2] + ... + pSrc[blockSize-1]
|
|
|
59 * </pre>
|
|
|
60 *
|
|
|
61 * There are separate functions for floating point, Q31, and Q15 data types.
|
|
|
62 */
|
|
|
63
|
|
|
64 /**
|
|
|
65 * @addtogroup STD
|
|
|
66 * @{
|
|
|
67 */
|
|
|
68
|
|
|
69
|
|
|
70 /**
|
|
|
71 * @brief Standard deviation of the elements of a floating-point vector.
|
|
|
72 * @param[in] *pSrc points to the input vector
|
|
|
73 * @param[in] blockSize length of the input vector
|
|
|
74 * @param[out] *pResult standard deviation value returned here
|
|
|
75 * @return none.
|
|
|
76 *
|
|
|
77 */
|
|
|
78
|
|
|
79
|
|
|
80 void arm_std_f32(
|
|
|
81 float32_t * pSrc,
|
|
|
82 uint32_t blockSize,
|
|
|
83 float32_t * pResult)
|
|
|
84 {
|
|
|
85 float32_t sum = 0.0f; /* Temporary result storage */
|
|
|
86 float32_t sumOfSquares = 0.0f; /* Sum of squares */
|
|
|
87 float32_t in; /* input value */
|
|
|
88 uint32_t blkCnt; /* loop counter */
|
|
|
89
|
|
|
90 #ifndef ARM_MATH_CM0_FAMILY
|
|
|
91
|
|
|
92 /* Run the below code for Cortex-M4 and Cortex-M3 */
|
|
|
93
|
|
|
94 float32_t meanOfSquares, mean, squareOfMean;
|
|
|
95
|
|
|
96 if(blockSize == 1)
|
|
|
97 {
|
|
|
98 *pResult = 0;
|
|
|
99 return;
|
|
|
100 }
|
|
|
101
|
|
|
102 /*loop Unrolling */
|
|
|
103 blkCnt = blockSize >> 2u;
|
|
|
104
|
|
|
105 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
|
|
|
106 ** a second loop below computes the remaining 1 to 3 samples. */
|
|
|
107 while(blkCnt > 0u)
|
|
|
108 {
|
|
|
109 /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
|
|
|
110 /* Compute Sum of squares of the input samples
|
|
|
111 * and then store the result in a temporary variable, sum. */
|
|
|
112 in = *pSrc++;
|
|
|
113 sum += in;
|
|
|
114 sumOfSquares += in * in;
|
|
|
115 in = *pSrc++;
|
|
|
116 sum += in;
|
|
|
117 sumOfSquares += in * in;
|
|
|
118 in = *pSrc++;
|
|
|
119 sum += in;
|
|
|
120 sumOfSquares += in * in;
|
|
|
121 in = *pSrc++;
|
|
|
122 sum += in;
|
|
|
123 sumOfSquares += in * in;
|
|
|
124
|
|
|
125 /* Decrement the loop counter */
|
|
|
126 blkCnt--;
|
|
|
127 }
|
|
|
128
|
|
|
129 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
|
|
|
130 ** No loop unrolling is used. */
|
|
|
131 blkCnt = blockSize % 0x4u;
|
|
|
132
|
|
|
133 while(blkCnt > 0u)
|
|
|
134 {
|
|
|
135 /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
|
|
|
136 /* Compute Sum of squares of the input samples
|
|
|
137 * and then store the result in a temporary variable, sum. */
|
|
|
138 in = *pSrc++;
|
|
|
139 sum += in;
|
|
|
140 sumOfSquares += in * in;
|
|
|
141
|
|
|
142 /* Decrement the loop counter */
|
|
|
143 blkCnt--;
|
|
|
144 }
|
|
|
145
|
|
|
146 /* Compute Mean of squares of the input samples
|
|
|
147 * and then store the result in a temporary variable, meanOfSquares. */
|
|
|
148 meanOfSquares = sumOfSquares / ((float32_t) blockSize - 1.0f);
|
|
|
149
|
|
|
150 /* Compute mean of all input values */
|
|
|
151 mean = sum / (float32_t) blockSize;
|
|
|
152
|
|
|
153 /* Compute square of mean */
|
|
|
154 squareOfMean = (mean * mean) * (((float32_t) blockSize) /
|
|
|
155 ((float32_t) blockSize - 1.0f));
|
|
|
156
|
|
|
157 /* Compute standard deviation and then store the result to the destination */
|
|
|
158 arm_sqrt_f32((meanOfSquares - squareOfMean), pResult);
|
|
|
159
|
|
|
160 #else
|
|
|
161
|
|
|
162 /* Run the below code for Cortex-M0 */
|
|
|
163
|
|
|
164 float32_t squareOfSum; /* Square of Sum */
|
|
|
165 float32_t var; /* Temporary varaince storage */
|
|
|
166
|
|
|
167 if(blockSize == 1)
|
|
|
168 {
|
|
|
169 *pResult = 0;
|
|
|
170 return;
|
|
|
171 }
|
|
|
172
|
|
|
173 /* Loop over blockSize number of values */
|
|
|
174 blkCnt = blockSize;
|
|
|
175
|
|
|
176 while(blkCnt > 0u)
|
|
|
177 {
|
|
|
178 /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
|
|
|
179 /* Compute Sum of squares of the input samples
|
|
|
180 * and then store the result in a temporary variable, sumOfSquares. */
|
|
|
181 in = *pSrc++;
|
|
|
182 sumOfSquares += in * in;
|
|
|
183
|
|
|
184 /* C = (A[0] + A[1] + ... + A[blockSize-1]) */
|
|
|
185 /* Compute Sum of the input samples
|
|
|
186 * and then store the result in a temporary variable, sum. */
|
|
|
187 sum += in;
|
|
|
188
|
|
|
189 /* Decrement the loop counter */
|
|
|
190 blkCnt--;
|
|
|
191 }
|
|
|
192
|
|
|
193 /* Compute the square of sum */
|
|
|
194 squareOfSum = ((sum * sum) / (float32_t) blockSize);
|
|
|
195
|
|
|
196 /* Compute the variance */
|
|
|
197 var = ((sumOfSquares - squareOfSum) / (float32_t) (blockSize - 1.0f));
|
|
|
198
|
|
|
199 /* Compute standard deviation and then store the result to the destination */
|
|
|
200 arm_sqrt_f32(var, pResult);
|
|
|
201
|
|
|
202 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
|
|
|
203
|
|
|
204 }
|
|
|
205
|
|
|
206 /**
|
|
|
207 * @} end of STD group
|
|
|
208 */
|
