hardware/arduino/sam/system/CMSIS/CMSIS/DSP_Lib/Source/StatisticsFunctions/arm_std_q31.c - platform/external/arduino-ide - Git at Google

 /* ----------------------------------------------------------------------
 * 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
  */
	/* ----------------------------------------------------------------------
	* 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
	*/