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| 8b51c7 | 1 | /* ---------------------------------------------------------------------- |
| Q | 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 | */ | |
