You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
186 lines
6.4 KiB
186 lines
6.4 KiB
/* ----------------------------------------------------------------------
|
|
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
|
|
*
|
|
* $Date: 19. March 2015
|
|
* $Revision: V.1.4.5
|
|
*
|
|
* Project: CMSIS DSP Library
|
|
* Title: arm_std_q31.c
|
|
*
|
|
* Description: Standard deviation of an array of Q31 type.
|
|
*
|
|
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* - Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* - Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in
|
|
* the documentation and/or other materials provided with the
|
|
* distribution.
|
|
* - Neither the name of ARM LIMITED nor the names of its contributors
|
|
* may be used to endorse or promote products derived from this
|
|
* software without specific prior written permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
|
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
|
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
|
|
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
|
|
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
|
|
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
|
|
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
|
|
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
|
|
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
* POSSIBILITY OF SUCH DAMAGE.
|
|
* -------------------------------------------------------------------- */
|
|
|
|
#include "arm_math.h"
|
|
|
|
/**
|
|
* @ingroup groupStats
|
|
*/
|
|
|
|
/**
|
|
* @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
|
|
* <b>Scaling and Overflow Behavior:</b>
|
|
*
|
|
*\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.
|
|
*
|
|
*/
|
|
|
|
|
|
void arm_std_q31(
|
|
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 */
|
|
|
|
if(blockSize == 1)
|
|
{
|
|
*pResult = 0;
|
|
return;
|
|
}
|
|
|
|
#ifndef ARM_MATH_CM0_FAMILY
|
|
|
|
/* Run the below code for Cortex-M4 and Cortex-M3 */
|
|
|
|
/*loop Unrolling */
|
|
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. */
|
|
in = *pSrc++ >> 8;
|
|
sum += in;
|
|
sumOfSquares += ((q63_t) (in) * (in));
|
|
in = *pSrc++ >> 8;
|
|
sum += in;
|
|
sumOfSquares += ((q63_t) (in) * (in));
|
|
in = *pSrc++ >> 8;
|
|
sum += in;
|
|
sumOfSquares += ((q63_t) (in) * (in));
|
|
in = *pSrc++ >> 8;
|
|
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++ >> 8;
|
|
sum += in;
|
|
sumOfSquares += ((q63_t) (in) * (in));
|
|
|
|
/* Decrement the 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 - 1);
|
|
|
|
#else
|
|
|
|
/* Run the below code for Cortex-M0 */
|
|
|
|
/* Loop over blockSize number of values */
|
|
blkCnt = blockSize;
|
|
|
|
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. */
|
|
in = *pSrc++ >> 8;
|
|
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. */
|
|
sum += in;
|
|
|
|
/* Decrement the 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 - 1);
|
|
|
|
#endif /* #ifndef ARM_MATH_CM0_FAMILY */
|
|
|
|
/* Compute square of mean */
|
|
squareOfMean = sum * sum / (q63_t)(blockSize * (blockSize - 1u));
|
|
|
|
/* Compute standard deviation and then store the result to the destination */
|
|
arm_sqrt_q31((meanOfSquares - squareOfMean) >> 15, pResult);
|
|
|
|
}
|
|
|
|
/**
|
|
* @} end of STD group
|
|
*/
|
|
|