From 96d6da4e252b06dcfdc041e7df23e86161c33007 Mon Sep 17 00:00:00 2001 From: rihab kouki Date: Tue, 28 Jul 2020 11:24:49 +0100 Subject: Official ARM version: v5.6.0 --- DSP/Source/StatisticsFunctions/arm_std_q31.c | 148 ++++++++++++--------------- 1 file changed, 63 insertions(+), 85 deletions(-) (limited to 'DSP/Source/StatisticsFunctions/arm_std_q31.c') diff --git a/DSP/Source/StatisticsFunctions/arm_std_q31.c b/DSP/Source/StatisticsFunctions/arm_std_q31.c index f02cbdd..cfb6cb8 100644 --- a/DSP/Source/StatisticsFunctions/arm_std_q31.c +++ b/DSP/Source/StatisticsFunctions/arm_std_q31.c @@ -1,15 +1,15 @@ /* ---------------------------------------------------------------------- * Project: CMSIS DSP Library * Title: arm_std_q31.c - * Description: Standard deviation of an array of Q31 type. + * Description: Standard deviation of the elements of a Q31 vector * - * $Date: 27. January 2017 - * $Revision: V.1.5.1 + * $Date: 18. March 2019 + * $Revision: V1.6.0 * * Target Processor: Cortex-M cores * -------------------------------------------------------------------- */ /* - * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved. + * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved. * * SPDX-License-Identifier: Apache-2.0 * @@ -29,141 +29,119 @@ #include "arm_math.h" /** - * @ingroup groupStats + @ingroup groupStats */ /** - * @addtogroup STD - * @{ + @addtogroup STD + @{ */ /** - * @brief Standard deviation of the elements of a Q31 vector. - * @param[in] *pSrc points to the input vector - * @param[in] blockSize length of the input vector - * @param[out] *pResult standard deviation value returned here - * @return none. - * @details - * Scaling and Overflow Behavior: - * - *\par - * The function is implemented using an internal 64-bit accumulator. - * The input is represented in 1.31 format, which is then downshifted by 8 bits - * which yields 1.23, and intermediate multiplication yields a 2.46 format. - * The accumulator maintains full precision of the intermediate multiplication results, - * but provides only a 16 guard bits. - * There is no saturation on intermediate additions. - * If the accumulator overflows it wraps around and distorts the result. - * In order to avoid overflows completely the input signal must be scaled down by - * log2(blockSize)-8 bits, as a total of blockSize additions are performed internally. - * After division, internal variables should be Q18.46 - * Finally, the 18.46 accumulator is right shifted by 15 bits to yield a 1.31 format value. - * + @brief Standard deviation of the elements of a Q31 vector. + @param[in] pSrc points to the input vector. + @param[in] blockSize number of samples in input vector. + @param[out] pResult standard deviation value returned here. + @return none + + @par Scaling and Overflow Behavior + The function is implemented using an internal 64-bit accumulator. + The input is represented in 1.31 format, which is then downshifted by 8 bits + which yields 1.23, and intermediate multiplication yields a 2.46 format. + The accumulator maintains full precision of the intermediate multiplication results, + but provides only a 16 guard bits. + There is no saturation on intermediate additions. + If the accumulator overflows it wraps around and distorts the result. + In order to avoid overflows completely the input signal must be scaled down by + log2(blockSize)-8 bits, as a total of blockSize additions are performed internally. + After division, internal variables should be Q18.46 + Finally, the 18.46 accumulator is right shifted by 15 bits to yield a 1.31 format value. */ void arm_std_q31( - q31_t * pSrc, - uint32_t blockSize, - q31_t * pResult) + const q31_t * pSrc, + uint32_t blockSize, + q31_t * pResult) { - q63_t sum = 0; /* Accumulator */ - q63_t meanOfSquares, squareOfMean; /* square of mean and mean of square */ - q31_t in; /* input value */ - uint32_t blkCnt; /* loop counter */ - q63_t sumOfSquares = 0; /* Accumulator */ + uint32_t blkCnt; /* Loop counter */ + q63_t sum = 0; /* Accumulator */ + q63_t meanOfSquares, squareOfMean; /* Square of mean and mean of square */ + q63_t sumOfSquares = 0; /* Sum of squares */ + q31_t in; /* Temporary variable to store input value */ - if (blockSize == 1U) + if (blockSize <= 1U) { *pResult = 0; return; } -#if defined (ARM_MATH_DSP) - /* Run the below code for Cortex-M4 and Cortex-M3 */ +#if defined (ARM_MATH_LOOPUNROLL) - /*loop Unrolling */ + /* Loop unrolling: Compute 4 outputs at a time */ blkCnt = blockSize >> 2U; - /* First part of the processing with loop unrolling. Compute 4 outputs at a time. - ** a second loop below computes the remaining 1 to 3 samples. */ while (blkCnt > 0U) { - /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */ - /* Compute Sum of squares of the input samples - * and then store the result in a temporary variable, sum. */ + /* C = A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1] */ + /* C = A[0] + A[1] + ... + A[blockSize-1] */ + in = *pSrc++ >> 8U; - sum += in; + /* Compute sum of squares and store result in a temporary variable, sumOfSquares. */ sumOfSquares += ((q63_t) (in) * (in)); - in = *pSrc++ >> 8U; + /* Compute sum and store result in a temporary variable, sum. */ sum += in; - sumOfSquares += ((q63_t) (in) * (in)); + in = *pSrc++ >> 8U; - sum += in; sumOfSquares += ((q63_t) (in) * (in)); - in = *pSrc++ >> 8U; sum += in; - sumOfSquares += ((q63_t) (in) * (in)); - - /* Decrement the loop counter */ - blkCnt--; - } - /* If the blockSize is not a multiple of 4, compute any remaining output samples here. - ** No loop unrolling is used. */ - blkCnt = blockSize % 0x4U; - - while (blkCnt > 0U) - { - /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */ - /* Compute Sum of squares of the input samples - * and then store the result in a temporary variable, sum. */ in = *pSrc++ >> 8U; + sumOfSquares += ((q63_t) (in) * (in)); sum += in; + + in = *pSrc++ >> 8U; sumOfSquares += ((q63_t) (in) * (in)); + sum += in; - /* Decrement the loop counter */ + /* Decrement loop counter */ blkCnt--; } - /* Compute Mean of squares of the input samples - * and then store the result in a temporary variable, meanOfSquares. */ - meanOfSquares = sumOfSquares / (q63_t)(blockSize - 1U); + /* Loop unrolling: Compute remaining outputs */ + blkCnt = blockSize % 0x4U; #else - /* Run the below code for Cortex-M0 */ - /* Loop over blockSize number of values */ + /* Initialize blkCnt with number of samples */ blkCnt = blockSize; +#endif /* #if defined (ARM_MATH_LOOPUNROLL) */ + while (blkCnt > 0U) { - /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */ - /* Compute Sum of squares of the input samples - * and then store the result in a temporary variable, sumOfSquares. */ + /* C = A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1] */ + /* C = A[0] + A[1] + ... + A[blockSize-1] */ + in = *pSrc++ >> 8U; + /* Compute sum of squares and store result in a temporary variable, sumOfSquares. */ sumOfSquares += ((q63_t) (in) * (in)); - - /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */ - /* Compute sum of all input values and then store the result in a temporary variable, sum. */ + /* Compute sum and store result in a temporary variable, sum. */ sum += in; - /* Decrement the loop counter */ + /* Decrement loop counter */ blkCnt--; } - /* Compute Mean of squares of the input samples - * and then store the result in a temporary variable, meanOfSquares. */ - meanOfSquares = sumOfSquares / (q63_t)(blockSize - 1U); - -#endif /* #if defined (ARM_MATH_DSP) */ + /* Compute Mean of squares and store result in a temporary variable, meanOfSquares. */ + meanOfSquares = (sumOfSquares / (q63_t)(blockSize - 1U)); /* Compute square of mean */ - squareOfMean = sum * sum / (q63_t)(blockSize * (blockSize - 1U)); + squareOfMean = ( sum * sum / (q63_t)(blockSize * (blockSize - 1U))); - /* Compute standard deviation and then store the result to the destination */ + /* Compute standard deviation and store result in destination */ arm_sqrt_q31((meanOfSquares - squareOfMean) >> 15U, pResult); } /** - * @} end of STD group + @} end of STD group */ -- cgit