DSP_Lib/Source/StatisticsFunctions/arm_std_q15.c - third_party/github/STMicroelectronics/cmsis_core - Git at Google

 /* ----------------------------------------------------------------------
 * 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_q15.c
 *
 * Description:	Standard deviation of an array of Q15 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 Q15 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 a 64-bit internal accumulator.
  * The input is represented in 1.15 format.
  * Intermediate multiplication yields a 2.30 format, and this
  * result is added without saturation to a 64-bit accumulator in 34.30 format.
  * With 33 guard bits in the accumulator, there is no risk of overflow, and the
  * full precision of the intermediate multiplication is preserved.
  * Finally, the 34.30 result is truncated to 34.15 format by discarding the lower
  * 15 bits, and then saturated to yield a result in 1.15 format.
  */

 void arm_std_q15(
   q15_t * pSrc,
   uint32_t blockSize,
   q15_t * pResult)
 {
   q31_t sum = 0;                                 /* Accumulator */
   q31_t meanOfSquares, squareOfMean;             /* square of mean and mean of square */
   uint32_t blkCnt;                               /* loop counter */
   q63_t sumOfSquares = 0;                        /* Accumulator */

 #ifndef ARM_MATH_CM0_FAMILY

   /* Run the below code for Cortex-M4 and Cortex-M3 */

   q31_t in;                                      /* input value */
   q15_t in1;                                     /* input value */

 	if(blockSize == 1)
 	{
 		*pResult = 0;
 		return;
 	}

   /*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 = *__SIMD32(pSrc)++;
     sum += ((in << 16) >> 16);
     sum += (in >> 16);
     sumOfSquares = __SMLALD(in, in, sumOfSquares);
     in = *__SIMD32(pSrc)++;
     sum += ((in << 16) >> 16);
     sum += (in >> 16);
     sumOfSquares = __SMLALD(in, in, sumOfSquares);

     /* 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. */
     in1 = *pSrc++;
     sumOfSquares = __SMLALD(in1, in1, sumOfSquares);
     sum += in1;

     /* Decrement the loop counter */
     blkCnt--;
   }

   /* Compute Mean of squares of the input samples
    * and then store the result in a temporary variable, meanOfSquares. */
   meanOfSquares = (q31_t)(sumOfSquares / (q63_t)(blockSize - 1));

   /* Compute square of mean */
   squareOfMean = (q31_t) ((q63_t)sum * sum / (q63_t)(blockSize * (blockSize - 1)));

   /* mean of the squares minus the square of the mean. */
   /* Compute standard deviation and store the result to the destination */
   arm_sqrt_q15(__SSAT((meanOfSquares - squareOfMean) >> 15, 16u), pResult);

 #else

   /* Run the below code for Cortex-M0 */
   q15_t in;                                      /* input value */

 	if(blockSize == 1)
 	{
 		*pResult = 0;
 		return;
 	}

   /* 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 += (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 = (q31_t)(sumOfSquares / (q63_t)(blockSize - 1));

   /* Compute square of mean */
   squareOfMean = (q31_t) ((q63_t)sum * sum / (q63_t)(blockSize * (blockSize - 1)));

   /* mean of the squares minus the square of the mean. */
   /* Compute standard deviation and store the result to the destination */
   arm_sqrt_q15(__SSAT((meanOfSquares - squareOfMean) >> 15, 16u), pResult);

 #endif /* #ifndef ARM_MATH_CM0_FAMILY */


 }

 /**
  * @} end of STD group
  */
	/* ----------------------------------------------------------------------
	* 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_q15.c
	*
	* Description: Standard deviation of an array of Q15 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 Q15 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 a 64-bit internal accumulator.
	* The input is represented in 1.15 format.
	* Intermediate multiplication yields a 2.30 format, and this
	* result is added without saturation to a 64-bit accumulator in 34.30 format.
	* With 33 guard bits in the accumulator, there is no risk of overflow, and the
	* full precision of the intermediate multiplication is preserved.
	* Finally, the 34.30 result is truncated to 34.15 format by discarding the lower
	* 15 bits, and then saturated to yield a result in 1.15 format.
	*/

	void arm_std_q15(
	q15_t * pSrc,
	uint32_t blockSize,
	q15_t * pResult)
	{
	q31_t sum = 0; /* Accumulator */
	q31_t meanOfSquares, squareOfMean; /* square of mean and mean of square */
	uint32_t blkCnt; /* loop counter */
	q63_t sumOfSquares = 0; /* Accumulator */

	#ifndef ARM_MATH_CM0_FAMILY

	/* Run the below code for Cortex-M4 and Cortex-M3 */

	q31_t in; /* input value */
	q15_t in1; /* input value */

	if(blockSize == 1)
	{
	*pResult = 0;
	return;
	}

	/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 = *__SIMD32(pSrc)++;
	sum += ((in << 16) >> 16);
	sum += (in >> 16);
	sumOfSquares = __SMLALD(in, in, sumOfSquares);
	in = *__SIMD32(pSrc)++;
	sum += ((in << 16) >> 16);
	sum += (in >> 16);
	sumOfSquares = __SMLALD(in, in, sumOfSquares);

	/* 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. */
	in1 = *pSrc++;
	sumOfSquares = __SMLALD(in1, in1, sumOfSquares);
	sum += in1;

	/* Decrement the loop counter */
	blkCnt--;
	}

	/* Compute Mean of squares of the input samples
	* and then store the result in a temporary variable, meanOfSquares. */
	meanOfSquares = (q31_t)(sumOfSquares / (q63_t)(blockSize - 1));

	/* Compute square of mean */
	squareOfMean = (q31_t) ((q63_t)sum * sum / (q63_t)(blockSize * (blockSize - 1)));

	/* mean of the squares minus the square of the mean. */
	/* Compute standard deviation and store the result to the destination */
	arm_sqrt_q15(__SSAT((meanOfSquares - squareOfMean) >> 15, 16u), pResult);

	#else

	/* Run the below code for Cortex-M0 */
	q15_t in; /* input value */

	if(blockSize == 1)
	{
	*pResult = 0;
	return;
	}

	/* 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 += (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 = (q31_t)(sumOfSquares / (q63_t)(blockSize - 1));

	/* Compute square of mean */
	squareOfMean = (q31_t) ((q63_t)sum * sum / (q63_t)(blockSize * (blockSize - 1)));

	/* mean of the squares minus the square of the mean. */
	/* Compute standard deviation and store the result to the destination */
	arm_sqrt_q15(__SSAT((meanOfSquares - squareOfMean) >> 15, 16u), pResult);

	#endif /* #ifndef ARM_MATH_CM0_FAMILY */


	}

	/**
	* @} end of STD group
	*/