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CMSIS DSP library

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cmsis_dsp/StatisticsFunctions/arm_var_q31.c@5:3762170b6d4d, 2015-11-20 (annotated)

Committer:
mbed_official
Date:
Fri Nov 20 08:45:18 2015 +0000
Revision:
5:3762170b6d4d
Parent:
3:7a284390b0ce 
Synchronized with git revision 2eb940b9a73af188d3004a2575fdfbb05febe62b



Full URL: https://github.com/mbedmicro/mbed/commit/2eb940b9a73af188d3004a2575fdfbb05febe62b/



Added option to build rpc library. closes #1426

Who changed what in which revision?

UserRevisionLine numberNew contents of line
emilmont 1:fdd22bb7aa52 1 /* ----------------------------------------------------------------------
mbed_official 5:3762170b6d4d 2 * Copyright (C) 2010-2014 ARM Limited. All rights reserved.
emilmont 1:fdd22bb7aa52 3 *
mbed_official 5:3762170b6d4d 4 * $Date: 19. March 2015
mbed_official 5:3762170b6d4d 5 * $Revision: V.1.4.5
emilmont 1:fdd22bb7aa52 6 *
emilmont 2:da51fb522205 7 * Project: CMSIS DSP Library
emilmont 2:da51fb522205 8 * Title: arm_var_q31.c
emilmont 1:fdd22bb7aa52 9 *
emilmont 2:da51fb522205 10 * Description: Variance of an array of Q31 type.
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 * @addtogroup variance
emilmont 1:fdd22bb7aa52 49 * @{
emilmont 1:fdd22bb7aa52 50 */
emilmont 1:fdd22bb7aa52 51
emilmont 1:fdd22bb7aa52 52 /**
emilmont 1:fdd22bb7aa52 53 * @brief Variance of the elements of a Q31 vector.
emilmont 1:fdd22bb7aa52 54 * @param[in] *pSrc points to the input vector
emilmont 1:fdd22bb7aa52 55 * @param[in] blockSize length of the input vector
emilmont 1:fdd22bb7aa52 56 * @param[out] *pResult variance value returned here
emilmont 1:fdd22bb7aa52 57 * @return none.
emilmont 1:fdd22bb7aa52 58 *
emilmont 1:fdd22bb7aa52 59 * @details
emilmont 1:fdd22bb7aa52 60 * <b>Scaling and Overflow Behavior:</b>
emilmont 1:fdd22bb7aa52 61 *
emilmont 1:fdd22bb7aa52 62 *\par
emilmont 1:fdd22bb7aa52 63 * The function is implemented using an internal 64-bit accumulator.
mbed_official 5:3762170b6d4d 64 * The input is represented in 1.31 format, which is then downshifted by 8 bits
mbed_official 5:3762170b6d4d 65 * which yields 1.23, and intermediate multiplication yields a 2.46 format.
emilmont 1:fdd22bb7aa52 66 * The accumulator maintains full precision of the intermediate multiplication results,
mbed_official 5:3762170b6d4d 67 * but provides only a 16 guard bits.
emilmont 1:fdd22bb7aa52 68 * There is no saturation on intermediate additions.
emilmont 1:fdd22bb7aa52 69 * If the accumulator overflows it wraps around and distorts the result.
emilmont 1:fdd22bb7aa52 70 * In order to avoid overflows completely the input signal must be scaled down by
mbed_official 5:3762170b6d4d 71 * log2(blockSize)-8 bits, as a total of blockSize additions are performed internally.
mbed_official 5:3762170b6d4d 72 * After division, internal variables should be Q18.46
mbed_official 5:3762170b6d4d 73 * Finally, the 18.46 accumulator is right shifted by 15 bits to yield a 1.31 format value.
emilmont 1:fdd22bb7aa52 74 *
emilmont 1:fdd22bb7aa52 75 */
emilmont 1:fdd22bb7aa52 76
emilmont 1:fdd22bb7aa52 77
emilmont 1:fdd22bb7aa52 78 void arm_var_q31(
emilmont 1:fdd22bb7aa52 79 q31_t * pSrc,
emilmont 1:fdd22bb7aa52 80 uint32_t blockSize,
mbed_official 5:3762170b6d4d 81 q31_t * pResult)
emilmont 1:fdd22bb7aa52 82 {
mbed_official 5:3762170b6d4d 83 q63_t sum = 0; /* Accumulator */
mbed_official 5:3762170b6d4d 84 q63_t meanOfSquares, squareOfMean; /* square of mean and mean of square */
emilmont 1:fdd22bb7aa52 85 q31_t in; /* input value */
emilmont 1:fdd22bb7aa52 86 uint32_t blkCnt; /* loop counter */
mbed_official 5:3762170b6d4d 87 q63_t sumOfSquares = 0; /* Accumulator */
emilmont 1:fdd22bb7aa52 88
mbed_official 5:3762170b6d4d 89 if(blockSize == 1)
mbed_official 5:3762170b6d4d 90 {
mbed_official 5:3762170b6d4d 91 *pResult = 0;
mbed_official 5:3762170b6d4d 92 return;
mbed_official 5:3762170b6d4d 93 }
mbed_official 5:3762170b6d4d 94
mbed_official 3:7a284390b0ce 95 #ifndef ARM_MATH_CM0_FAMILY
emilmont 1:fdd22bb7aa52 96
emilmont 1:fdd22bb7aa52 97 /* Run the below code for Cortex-M4 and Cortex-M3 */
emilmont 1:fdd22bb7aa52 98
emilmont 1:fdd22bb7aa52 99 /*loop Unrolling */
emilmont 1:fdd22bb7aa52 100 blkCnt = blockSize >> 2u;
emilmont 1:fdd22bb7aa52 101
emilmont 1:fdd22bb7aa52 102 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
emilmont 1:fdd22bb7aa52 103 ** a second loop below computes the remaining 1 to 3 samples. */
emilmont 1:fdd22bb7aa52 104 while(blkCnt > 0u)
emilmont 1:fdd22bb7aa52 105 {
emilmont 1:fdd22bb7aa52 106 /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
mbed_official 5:3762170b6d4d 107 /* Compute Sum of squares of the input samples
emilmont 1:fdd22bb7aa52 108 * and then store the result in a temporary variable, sum. */
mbed_official 5:3762170b6d4d 109 in = *pSrc++ >> 8;
mbed_official 5:3762170b6d4d 110 sum += in;
mbed_official 5:3762170b6d4d 111 sumOfSquares += ((q63_t) (in) * (in));
mbed_official 5:3762170b6d4d 112 in = *pSrc++ >> 8;
mbed_official 5:3762170b6d4d 113 sum += in;
mbed_official 5:3762170b6d4d 114 sumOfSquares += ((q63_t) (in) * (in));
mbed_official 5:3762170b6d4d 115 in = *pSrc++ >> 8;
mbed_official 5:3762170b6d4d 116 sum += in;
mbed_official 5:3762170b6d4d 117 sumOfSquares += ((q63_t) (in) * (in));
mbed_official 5:3762170b6d4d 118 in = *pSrc++ >> 8;
mbed_official 5:3762170b6d4d 119 sum += in;
mbed_official 5:3762170b6d4d 120 sumOfSquares += ((q63_t) (in) * (in));
emilmont 1:fdd22bb7aa52 121
emilmont 1:fdd22bb7aa52 122 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 123 blkCnt--;
emilmont 1:fdd22bb7aa52 124 }
emilmont 1:fdd22bb7aa52 125
emilmont 1:fdd22bb7aa52 126 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
emilmont 1:fdd22bb7aa52 127 ** No loop unrolling is used. */
emilmont 1:fdd22bb7aa52 128 blkCnt = blockSize % 0x4u;
emilmont 1:fdd22bb7aa52 129
mbed_official 5:3762170b6d4d 130 while(blkCnt > 0u)
mbed_official 5:3762170b6d4d 131 {
mbed_official 5:3762170b6d4d 132 /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
mbed_official 5:3762170b6d4d 133 /* Compute Sum of squares of the input samples
mbed_official 5:3762170b6d4d 134 * and then store the result in a temporary variable, sum. */
mbed_official 5:3762170b6d4d 135 in = *pSrc++ >> 8;
mbed_official 5:3762170b6d4d 136 sum += in;
mbed_official 5:3762170b6d4d 137 sumOfSquares += ((q63_t) (in) * (in));
mbed_official 5:3762170b6d4d 138
mbed_official 5:3762170b6d4d 139 /* Decrement the loop counter */
mbed_official 5:3762170b6d4d 140 blkCnt--;
mbed_official 5:3762170b6d4d 141 }
mbed_official 5:3762170b6d4d 142
mbed_official 5:3762170b6d4d 143 /* Compute Mean of squares of the input samples
mbed_official 5:3762170b6d4d 144 * and then store the result in a temporary variable, meanOfSquares. */
mbed_official 5:3762170b6d4d 145 meanOfSquares = sumOfSquares / (q63_t)(blockSize - 1);
mbed_official 5:3762170b6d4d 146
emilmont 1:fdd22bb7aa52 147 #else
emilmont 1:fdd22bb7aa52 148
emilmont 1:fdd22bb7aa52 149 /* Run the below code for Cortex-M0 */
mbed_official 5:3762170b6d4d 150
mbed_official 5:3762170b6d4d 151 /* Loop over blockSize number of values */
emilmont 1:fdd22bb7aa52 152 blkCnt = blockSize;
emilmont 1:fdd22bb7aa52 153
emilmont 1:fdd22bb7aa52 154 while(blkCnt > 0u)
emilmont 1:fdd22bb7aa52 155 {
emilmont 1:fdd22bb7aa52 156 /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
mbed_official 5:3762170b6d4d 157 /* Compute Sum of squares of the input samples
mbed_official 5:3762170b6d4d 158 * and then store the result in a temporary variable, sumOfSquares. */
mbed_official 5:3762170b6d4d 159 in = *pSrc++ >> 8;
mbed_official 5:3762170b6d4d 160 sumOfSquares += ((q63_t) (in) * (in));
mbed_official 5:3762170b6d4d 161
mbed_official 5:3762170b6d4d 162 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
mbed_official 5:3762170b6d4d 163 /* Compute sum of all input values and then store the result in a temporary variable, sum. */
emilmont 1:fdd22bb7aa52 164 sum += in;
emilmont 1:fdd22bb7aa52 165
emilmont 1:fdd22bb7aa52 166 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 167 blkCnt--;
emilmont 1:fdd22bb7aa52 168 }
emilmont 1:fdd22bb7aa52 169
mbed_official 5:3762170b6d4d 170 /* Compute Mean of squares of the input samples
emilmont 1:fdd22bb7aa52 171 * and then store the result in a temporary variable, meanOfSquares. */
mbed_official 5:3762170b6d4d 172 meanOfSquares = sumOfSquares / (q63_t)(blockSize - 1);
emilmont 1:fdd22bb7aa52 173
mbed_official 5:3762170b6d4d 174 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
emilmont 1:fdd22bb7aa52 175
emilmont 1:fdd22bb7aa52 176 /* Compute square of mean */
mbed_official 5:3762170b6d4d 177 squareOfMean = sum * sum / (q63_t)(blockSize * (blockSize - 1u));
mbed_official 5:3762170b6d4d 178
emilmont 1:fdd22bb7aa52 179
mbed_official 5:3762170b6d4d 180 /* Compute standard deviation and then store the result to the destination */
mbed_official 5:3762170b6d4d 181 *pResult = (meanOfSquares - squareOfMean) >> 15;
emilmont 1:fdd22bb7aa52 182
emilmont 1:fdd22bb7aa52 183 }
emilmont 1:fdd22bb7aa52 184
emilmont 1:fdd22bb7aa52 185 /**
emilmont 1:fdd22bb7aa52 186 * @} end of variance group
emilmont 1:fdd22bb7aa52 187 */