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Removed error on fat32 library, seems now to be able navigate among sectors in...
Removed error on fat32 library, seems now to be able navigate among sectors in both directions. Improved SDLCD drawing performances by almost 1000x.
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arm_std_q31.c
219 lines | 6.8 KiB | text/x-c | CLexer
/ lib / src / stm32f4 / CPU / CMSIS / DSP_Lib / Source / StatisticsFunctions / arm_std_q31.c
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/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date: 15. July 2011
* $Revision: V1.0.10
*
* 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
*
* Version 1.0.10 2011/7/15
* Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
* Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
* Documentation updated.
*
* Version 1.0.1 2010/10/05
* Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
* Production release and review comments incorporated.
* -------------------------------------------------------------------- */
#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, and intermediate multiplication
* yields a 2.62 format.
* The accumulator maintains full precision of the intermediate multiplication results,
* but provides only a single guard bit.
* 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) bits, as a total of blockSize additions are performed internally.
* Finally, the 2.62 accumulator is right shifted by 31 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 */
q31_t meanOfSquares, squareOfMean; /* square of mean and mean of square */
q31_t mean; /* mean */
q31_t in; /* input value */
q31_t t; /* Temporary variable */
uint32_t blkCnt; /* loop counter */
#ifndef ARM_MATH_CM0
/* Run the below code for Cortex-M4 and Cortex-M3 */
q31_t *pIn; /* Temporary pointer */
pIn = pSrc;
/*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++;
sum += ((q63_t) (in) * (in));
in = *pSrc++;
sum += ((q63_t) (in) * (in));
in = *pSrc++;
sum += ((q63_t) (in) * (in));
in = *pSrc++;
sum += ((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++;
sum += ((q63_t) (in) * (in));
/* Decrement the loop counter */
blkCnt--;
}
t = (q31_t) ((1.0f / (float32_t) (blockSize - 1u)) * 1073741824.0f);
/* Compute Mean of squares of the input samples
* and then store the result in a temporary variable, meanOfSquares. */
sum = (sum >> 31);
meanOfSquares = (q31_t) ((sum * t) >> 30);
/* Reset the accumulator */
sum = 0;
/*loop Unrolling */
blkCnt = blockSize >> 2u;
/* Reset the input working pointer */
pSrc = pIn;
/* 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[1] + A[2] + ... + A[blockSize-1]) */
/* Compute sum of all input values and then store the result in a temporary variable, sum. */
sum += *pSrc++;
sum += *pSrc++;
sum += *pSrc++;
sum += *pSrc++;
/* 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[1] + A[2] + ... + A[blockSize-1]) */
/* Compute sum of all input values and then store the result in a temporary variable, sum. */
sum += *pSrc++;
/* Decrement the loop counter */
blkCnt--;
}
#else
/* Run the below code for Cortex-M0 */
q63_t sumOfSquares = 0; /* Accumulator */
/* 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++;
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. */
t = (q31_t) ((1.0f / (float32_t) (blockSize - 1u)) * 1073741824.0f);
sumOfSquares = (sumOfSquares >> 31);
meanOfSquares = (q31_t) ((sumOfSquares * t) >> 30);
#endif /* #ifndef ARM_MATH_CM0 */
/* Compute mean of all input values */
t = (q31_t) ((1.0f / (blockSize * (blockSize - 1u))) * 2147483648.0f);
mean = (q31_t) (sum);
/* Compute square of mean */
squareOfMean = (q31_t) (((q63_t) mean * mean) >> 31);
squareOfMean = (q31_t) (((q63_t) squareOfMean * t) >> 31);
/* Compute standard deviation and then store the result to the destination */
arm_sqrt_q31(meanOfSquares - squareOfMean, pResult);
}
/**
* @} end of STD group
*/