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