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comparison f103c8/Drivers/CMSIS/DSP_Lib/Source/StatisticsFunctions/arm_std_q31.c @ 2:0c59e7a7782a

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Working on GPIO and RCC
author cin
date Mon, 16 Jan 2017 11:04:47 +0300
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1:a0b14b11ad9f 2:0c59e7a7782a
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_q31.c
9 *
10 * Description: Standard deviation of an array of Q31 type.
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 * @addtogroup STD
49 * @{
50 */
51
52
53 /**
54 * @brief Standard deviation of the elements of a Q31 vector.
55 * @param[in] *pSrc points to the input vector
56 * @param[in] blockSize length of the input vector
57 * @param[out] *pResult standard deviation value returned here
58 * @return none.
59 * @details
60 * <b>Scaling and Overflow Behavior:</b>
61 *
62 *\par
63 * The function is implemented using an internal 64-bit accumulator.
64 * The input is represented in 1.31 format, which is then downshifted by 8 bits
65 * which yields 1.23, and intermediate multiplication yields a 2.46 format.
66 * The accumulator maintains full precision of the intermediate multiplication results,
67 * but provides only a 16 guard bits.
68 * There is no saturation on intermediate additions.
69 * If the accumulator overflows it wraps around and distorts the result.
70 * In order to avoid overflows completely the input signal must be scaled down by
71 * log2(blockSize)-8 bits, as a total of blockSize additions are performed internally.
72 * After division, internal variables should be Q18.46
73 * Finally, the 18.46 accumulator is right shifted by 15 bits to yield a 1.31 format value.
74 *
75 */
76
77
78 void arm_std_q31(
79 q31_t * pSrc,
80 uint32_t blockSize,
81 q31_t * pResult)
82 {
83 q63_t sum = 0; /* Accumulator */
84 q63_t meanOfSquares, squareOfMean; /* square of mean and mean of square */
85 q31_t in; /* input value */
86 uint32_t blkCnt; /* loop counter */
87 q63_t sumOfSquares = 0; /* Accumulator */
88
89 if(blockSize == 1)
90 {
91 *pResult = 0;
92 return;
93 }
94
95 #ifndef ARM_MATH_CM0_FAMILY
96
97 /* Run the below code for Cortex-M4 and Cortex-M3 */
98
99 /*loop Unrolling */
100 blkCnt = blockSize >> 2u;
101
102 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
103 ** a second loop below computes the remaining 1 to 3 samples. */
104 while(blkCnt > 0u)
105 {
106 /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
107 /* Compute Sum of squares of the input samples
108 * and then store the result in a temporary variable, sum. */
109 in = *pSrc++ >> 8;
110 sum += in;
111 sumOfSquares += ((q63_t) (in) * (in));
112 in = *pSrc++ >> 8;
113 sum += in;
114 sumOfSquares += ((q63_t) (in) * (in));
115 in = *pSrc++ >> 8;
116 sum += in;
117 sumOfSquares += ((q63_t) (in) * (in));
118 in = *pSrc++ >> 8;
119 sum += in;
120 sumOfSquares += ((q63_t) (in) * (in));
121
122 /* Decrement the loop counter */
123 blkCnt--;
124 }
125
126 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
127 ** No loop unrolling is used. */
128 blkCnt = blockSize % 0x4u;
129
130 while(blkCnt > 0u)
131 {
132 /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
133 /* Compute Sum of squares of the input samples
134 * and then store the result in a temporary variable, sum. */
135 in = *pSrc++ >> 8;
136 sum += in;
137 sumOfSquares += ((q63_t) (in) * (in));
138
139 /* Decrement the loop counter */
140 blkCnt--;
141 }
142
143 /* Compute Mean of squares of the input samples
144 * and then store the result in a temporary variable, meanOfSquares. */
145 meanOfSquares = sumOfSquares / (q63_t)(blockSize - 1);
146
147 #else
148
149 /* Run the below code for Cortex-M0 */
150
151 /* Loop over blockSize number of values */
152 blkCnt = blockSize;
153
154 while(blkCnt > 0u)
155 {
156 /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
157 /* Compute Sum of squares of the input samples
158 * and then store the result in a temporary variable, sumOfSquares. */
159 in = *pSrc++ >> 8;
160 sumOfSquares += ((q63_t) (in) * (in));
161
162 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
163 /* Compute sum of all input values and then store the result in a temporary variable, sum. */
164 sum += in;
165
166 /* Decrement the loop counter */
167 blkCnt--;
168 }
169
170 /* Compute Mean of squares of the input samples
171 * and then store the result in a temporary variable, meanOfSquares. */
172 meanOfSquares = sumOfSquares / (q63_t)(blockSize - 1);
173
174 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
175
176 /* Compute square of mean */
177 squareOfMean = sum * sum / (q63_t)(blockSize * (blockSize - 1u));
178
179 /* Compute standard deviation and then store the result to the destination */
180 arm_sqrt_q31((meanOfSquares - squareOfMean) >> 15, pResult);
181
182 }
183
184 /**
185 * @} end of STD group
186 */