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CMSIS DSP library

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cmsis_dsp/StatisticsFunctions/arm_var_f32.c@3:7a284390b0ce, 2013-11-08 (annotated)

Committer:
mbed_official
Date:
Fri Nov 08 13:45:10 2013 +0000
Revision:
3:7a284390b0ce
Parent:
2:da51fb522205
Child:
5:3762170b6d4d
Synchronized with git revision e69956aba2f68a2a26ac26b051f8d349deaa1ce8

Who changed what in which revision?

UserRevisionLine numberNew contents of line
emilmont 1:fdd22bb7aa52 1 /* ----------------------------------------------------------------------
mbed_official 3:7a284390b0ce 2 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.
emilmont 1:fdd22bb7aa52 3 *
mbed_official 3:7a284390b0ce 4 * $Date: 17. January 2013
mbed_official 3:7a284390b0ce 5 * $Revision: V1.4.1
emilmont 1:fdd22bb7aa52 6 *
emilmont 2:da51fb522205 7 * Project: CMSIS DSP Library
emilmont 2:da51fb522205 8 * Title: arm_var_f32.c
emilmont 1:fdd22bb7aa52 9 *
emilmont 2:da51fb522205 10 * Description: Variance of the elements of a floating-point vector.
emilmont 1:fdd22bb7aa52 11 *
emilmont 1:fdd22bb7aa52 12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
emilmont 1:fdd22bb7aa52 13 *
mbed_official 3:7a284390b0ce 14 * Redistribution and use in source and binary forms, with or without
mbed_official 3:7a284390b0ce 15 * modification, are permitted provided that the following conditions
mbed_official 3:7a284390b0ce 16 * are met:
mbed_official 3:7a284390b0ce 17 * - Redistributions of source code must retain the above copyright
mbed_official 3:7a284390b0ce 18 * notice, this list of conditions and the following disclaimer.
mbed_official 3:7a284390b0ce 19 * - Redistributions in binary form must reproduce the above copyright
mbed_official 3:7a284390b0ce 20 * notice, this list of conditions and the following disclaimer in
mbed_official 3:7a284390b0ce 21 * the documentation and/or other materials provided with the
mbed_official 3:7a284390b0ce 22 * distribution.
mbed_official 3:7a284390b0ce 23 * - Neither the name of ARM LIMITED nor the names of its contributors
mbed_official 3:7a284390b0ce 24 * may be used to endorse or promote products derived from this
mbed_official 3:7a284390b0ce 25 * software without specific prior written permission.
mbed_official 3:7a284390b0ce 26 *
mbed_official 3:7a284390b0ce 27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
mbed_official 3:7a284390b0ce 28 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
mbed_official 3:7a284390b0ce 29 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
mbed_official 3:7a284390b0ce 30 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
mbed_official 3:7a284390b0ce 31 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
mbed_official 3:7a284390b0ce 32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
mbed_official 3:7a284390b0ce 33 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
mbed_official 3:7a284390b0ce 34 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
mbed_official 3:7a284390b0ce 35 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
mbed_official 3:7a284390b0ce 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
mbed_official 3:7a284390b0ce 37 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
mbed_official 3:7a284390b0ce 38 * POSSIBILITY OF SUCH DAMAGE.
emilmont 1:fdd22bb7aa52 39 * ---------------------------------------------------------------------------- */
emilmont 1:fdd22bb7aa52 40
emilmont 1:fdd22bb7aa52 41 #include "arm_math.h"
emilmont 1:fdd22bb7aa52 42
emilmont 1:fdd22bb7aa52 43 /**
emilmont 1:fdd22bb7aa52 44 * @ingroup groupStats
emilmont 1:fdd22bb7aa52 45 */
emilmont 1:fdd22bb7aa52 46
emilmont 1:fdd22bb7aa52 47 /**
emilmont 1:fdd22bb7aa52 48 * @defgroup variance Variance
emilmont 1:fdd22bb7aa52 49 *
emilmont 1:fdd22bb7aa52 50 * Calculates the variance of the elements in the input vector.
emilmont 1:fdd22bb7aa52 51 * The underlying algorithm is used:
emilmont 1:fdd22bb7aa52 52 *
emilmont 1:fdd22bb7aa52 53 * <pre>
emilmont 2:da51fb522205 54 * Result = (sumOfSquares - sum<sup>2</sup> / blockSize) / (blockSize - 1)
emilmont 1:fdd22bb7aa52 55 *
emilmont 2:da51fb522205 56 * where, sumOfSquares = pSrc[0] * pSrc[0] + pSrc[1] * pSrc[1] + ... + pSrc[blockSize-1] * pSrc[blockSize-1]
emilmont 1:fdd22bb7aa52 57 *
emilmont 2:da51fb522205 58 * sum = pSrc[0] + pSrc[1] + pSrc[2] + ... + pSrc[blockSize-1]
emilmont 1:fdd22bb7aa52 59 * </pre>
emilmont 1:fdd22bb7aa52 60 *
emilmont 1:fdd22bb7aa52 61 * There are separate functions for floating point, Q31, and Q15 data types.
emilmont 1:fdd22bb7aa52 62 */
emilmont 1:fdd22bb7aa52 63
emilmont 1:fdd22bb7aa52 64 /**
emilmont 1:fdd22bb7aa52 65 * @addtogroup variance
emilmont 1:fdd22bb7aa52 66 * @{
emilmont 1:fdd22bb7aa52 67 */
emilmont 1:fdd22bb7aa52 68
emilmont 1:fdd22bb7aa52 69
emilmont 1:fdd22bb7aa52 70 /**
emilmont 1:fdd22bb7aa52 71 * @brief Variance of the elements of a floating-point vector.
emilmont 1:fdd22bb7aa52 72 * @param[in] *pSrc points to the input vector
emilmont 1:fdd22bb7aa52 73 * @param[in] blockSize length of the input vector
emilmont 1:fdd22bb7aa52 74 * @param[out] *pResult variance value returned here
emilmont 1:fdd22bb7aa52 75 * @return none.
emilmont 1:fdd22bb7aa52 76 *
emilmont 1:fdd22bb7aa52 77 */
emilmont 1:fdd22bb7aa52 78
emilmont 1:fdd22bb7aa52 79
emilmont 1:fdd22bb7aa52 80 void arm_var_f32(
emilmont 1:fdd22bb7aa52 81 float32_t * pSrc,
emilmont 1:fdd22bb7aa52 82 uint32_t blockSize,
emilmont 1:fdd22bb7aa52 83 float32_t * pResult)
emilmont 1:fdd22bb7aa52 84 {
emilmont 1:fdd22bb7aa52 85
emilmont 1:fdd22bb7aa52 86 float32_t sum = 0.0f; /* Temporary result storage */
emilmont 1:fdd22bb7aa52 87 float32_t sumOfSquares = 0.0f; /* Sum of squares */
emilmont 1:fdd22bb7aa52 88 float32_t in; /* input value */
emilmont 1:fdd22bb7aa52 89 uint32_t blkCnt; /* loop counter */
emilmont 1:fdd22bb7aa52 90
mbed_official 3:7a284390b0ce 91 #ifndef ARM_MATH_CM0_FAMILY
emilmont 1:fdd22bb7aa52 92
emilmont 1:fdd22bb7aa52 93 /* Run the below code for Cortex-M4 and Cortex-M3 */
emilmont 1:fdd22bb7aa52 94
emilmont 1:fdd22bb7aa52 95 float32_t meanOfSquares, mean, squareOfMean; /* Temporary variables */
emilmont 1:fdd22bb7aa52 96
emilmont 1:fdd22bb7aa52 97 /*loop Unrolling */
emilmont 1:fdd22bb7aa52 98 blkCnt = blockSize >> 2u;
emilmont 1:fdd22bb7aa52 99
emilmont 1:fdd22bb7aa52 100 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
emilmont 1:fdd22bb7aa52 101 ** a second loop below computes the remaining 1 to 3 samples. */
emilmont 1:fdd22bb7aa52 102 while(blkCnt > 0u)
emilmont 1:fdd22bb7aa52 103 {
emilmont 1:fdd22bb7aa52 104 /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
emilmont 1:fdd22bb7aa52 105 /* Compute Sum of squares of the input samples
emilmont 1:fdd22bb7aa52 106 * and then store the result in a temporary variable, sum. */
emilmont 1:fdd22bb7aa52 107 in = *pSrc++;
emilmont 1:fdd22bb7aa52 108 sum += in;
emilmont 1:fdd22bb7aa52 109 sumOfSquares += in * in;
emilmont 1:fdd22bb7aa52 110 in = *pSrc++;
emilmont 1:fdd22bb7aa52 111 sum += in;
emilmont 1:fdd22bb7aa52 112 sumOfSquares += in * in;
emilmont 1:fdd22bb7aa52 113 in = *pSrc++;
emilmont 1:fdd22bb7aa52 114 sum += in;
emilmont 1:fdd22bb7aa52 115 sumOfSquares += in * in;
emilmont 1:fdd22bb7aa52 116 in = *pSrc++;
emilmont 1:fdd22bb7aa52 117 sum += in;
emilmont 1:fdd22bb7aa52 118 sumOfSquares += in * in;
emilmont 1:fdd22bb7aa52 119
emilmont 1:fdd22bb7aa52 120 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 121 blkCnt--;
emilmont 1:fdd22bb7aa52 122 }
emilmont 1:fdd22bb7aa52 123
emilmont 1:fdd22bb7aa52 124 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
emilmont 1:fdd22bb7aa52 125 ** No loop unrolling is used. */
emilmont 1:fdd22bb7aa52 126 blkCnt = blockSize % 0x4u;
emilmont 1:fdd22bb7aa52 127
emilmont 1:fdd22bb7aa52 128 while(blkCnt > 0u)
emilmont 1:fdd22bb7aa52 129 {
emilmont 1:fdd22bb7aa52 130 /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
emilmont 1:fdd22bb7aa52 131 /* Compute Sum of squares of the input samples
emilmont 1:fdd22bb7aa52 132 * and then store the result in a temporary variable, sum. */
emilmont 1:fdd22bb7aa52 133 in = *pSrc++;
emilmont 1:fdd22bb7aa52 134 sum += in;
emilmont 1:fdd22bb7aa52 135 sumOfSquares += in * in;
emilmont 1:fdd22bb7aa52 136
emilmont 1:fdd22bb7aa52 137 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 138 blkCnt--;
emilmont 1:fdd22bb7aa52 139 }
emilmont 1:fdd22bb7aa52 140
emilmont 1:fdd22bb7aa52 141 /* Compute Mean of squares of the input samples
emilmont 1:fdd22bb7aa52 142 * and then store the result in a temporary variable, meanOfSquares. */
emilmont 1:fdd22bb7aa52 143 meanOfSquares = sumOfSquares / ((float32_t) blockSize - 1.0f);
emilmont 1:fdd22bb7aa52 144
emilmont 1:fdd22bb7aa52 145 /* Compute mean of all input values */
emilmont 1:fdd22bb7aa52 146 mean = sum / (float32_t) blockSize;
emilmont 1:fdd22bb7aa52 147
emilmont 1:fdd22bb7aa52 148 /* Compute square of mean */
emilmont 1:fdd22bb7aa52 149 squareOfMean = (mean * mean) * (((float32_t) blockSize) /
emilmont 1:fdd22bb7aa52 150 ((float32_t) blockSize - 1.0f));
emilmont 1:fdd22bb7aa52 151
emilmont 1:fdd22bb7aa52 152 /* Compute variance and then store the result to the destination */
emilmont 1:fdd22bb7aa52 153 *pResult = meanOfSquares - squareOfMean;
emilmont 1:fdd22bb7aa52 154
emilmont 1:fdd22bb7aa52 155 #else
emilmont 1:fdd22bb7aa52 156
emilmont 1:fdd22bb7aa52 157 /* Run the below code for Cortex-M0 */
emilmont 1:fdd22bb7aa52 158 float32_t squareOfSum; /* Square of Sum */
emilmont 1:fdd22bb7aa52 159
emilmont 1:fdd22bb7aa52 160 /* Loop over blockSize number of values */
emilmont 1:fdd22bb7aa52 161 blkCnt = blockSize;
emilmont 1:fdd22bb7aa52 162
emilmont 1:fdd22bb7aa52 163 while(blkCnt > 0u)
emilmont 1:fdd22bb7aa52 164 {
emilmont 1:fdd22bb7aa52 165 /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
emilmont 1:fdd22bb7aa52 166 /* Compute Sum of squares of the input samples
emilmont 1:fdd22bb7aa52 167 * and then store the result in a temporary variable, sumOfSquares. */
emilmont 1:fdd22bb7aa52 168 in = *pSrc++;
emilmont 1:fdd22bb7aa52 169 sumOfSquares += in * in;
emilmont 1:fdd22bb7aa52 170
emilmont 1:fdd22bb7aa52 171 /* C = (A[0] + A[1] + ... + A[blockSize-1]) */
emilmont 1:fdd22bb7aa52 172 /* Compute Sum of the input samples
emilmont 1:fdd22bb7aa52 173 * and then store the result in a temporary variable, sum. */
emilmont 1:fdd22bb7aa52 174 sum += in;
emilmont 1:fdd22bb7aa52 175
emilmont 1:fdd22bb7aa52 176 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 177 blkCnt--;
emilmont 1:fdd22bb7aa52 178 }
emilmont 1:fdd22bb7aa52 179
emilmont 1:fdd22bb7aa52 180 /* Compute the square of sum */
emilmont 1:fdd22bb7aa52 181 squareOfSum = ((sum * sum) / (float32_t) blockSize);
emilmont 1:fdd22bb7aa52 182
emilmont 1:fdd22bb7aa52 183 /* Compute the variance */
emilmont 1:fdd22bb7aa52 184 *pResult = ((sumOfSquares - squareOfSum) / (float32_t) (blockSize - 1.0f));
emilmont 1:fdd22bb7aa52 185
mbed_official 3:7a284390b0ce 186 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
emilmont 1:fdd22bb7aa52 187
emilmont 1:fdd22bb7aa52 188 }
emilmont 1:fdd22bb7aa52 189
emilmont 1:fdd22bb7aa52 190 /**
emilmont 1:fdd22bb7aa52 191 * @} end of variance group
emilmont 1:fdd22bb7aa52 192 */