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src/Cortex-M4-M3/StatisticsFunctions/arm_mean_q15.c@0:1014af42efd9, 2011-03-10 (annotated)

Committer:: simon
Date:: Thu Mar 10 15:07:50 2011 +0000
Revision:: 0:1014af42efd9

Who changed what in which revision?

User	Revision	Line number	New contents of line
simon	0:1014af42efd9	1	/* ----------------------------------------------------------------------
simon	0:1014af42efd9	2	* Copyright (C) 2010 ARM Limited. All rights reserved.
simon	0:1014af42efd9	3	*
simon	0:1014af42efd9	4	* $Date: 29. November 2010
simon	0:1014af42efd9	5	* $Revision: V1.0.3
simon	0:1014af42efd9	6	*
simon	0:1014af42efd9	7	* Project: CMSIS DSP Library
simon	0:1014af42efd9	8	* Title: arm_mean_q15.c
simon	0:1014af42efd9	9	*
simon	0:1014af42efd9	10	* Description: Mean value of two Q15 arrays.
simon	0:1014af42efd9	11	*
simon	0:1014af42efd9	12	* Target Processor: Cortex-M4/Cortex-M3
simon	0:1014af42efd9	13	*
simon	0:1014af42efd9	14	* Version 1.0.3 2010/11/29
simon	0:1014af42efd9	15	* Re-organized the CMSIS folders and updated documentation.
simon	0:1014af42efd9	16	*
simon	0:1014af42efd9	17	* Version 1.0.2 2010/11/11
simon	0:1014af42efd9	18	* Documentation updated.
simon	0:1014af42efd9	19	*
simon	0:1014af42efd9	20	* Version 1.0.1 2010/10/05
simon	0:1014af42efd9	21	* Production release and review comments incorporated.
simon	0:1014af42efd9	22	*
simon	0:1014af42efd9	23	* Version 1.0.0 2010/09/20
simon	0:1014af42efd9	24	* Production release and review comments incorporated.
simon	0:1014af42efd9	25	* -------------------------------------------------------------------- */
simon	0:1014af42efd9	26
simon	0:1014af42efd9	27	#include "arm_math.h"
simon	0:1014af42efd9	28
simon	0:1014af42efd9	29	/**
simon	0:1014af42efd9	30	* @ingroup groupStats
simon	0:1014af42efd9	31	*/
simon	0:1014af42efd9	32
simon	0:1014af42efd9	33	/**
simon	0:1014af42efd9	34	* @addtogroup mean
simon	0:1014af42efd9	35	* @{
simon	0:1014af42efd9	36	*/
simon	0:1014af42efd9	37
simon	0:1014af42efd9	38	/**
simon	0:1014af42efd9	39	* @brief Mean value of a Q15 vector.
simon	0:1014af42efd9	40	* @param[in] *pSrc points to the input vector
simon	0:1014af42efd9	41	* @param[in] blockSize length of the input vector
simon	0:1014af42efd9	42	* @param[out] *pResult mean value returned here
simon	0:1014af42efd9	43	* @return none.
simon	0:1014af42efd9	44	*
simon	0:1014af42efd9	45	* @details
simon	0:1014af42efd9	46	* <b>Scaling and Overflow Behavior:</b>
simon	0:1014af42efd9	47	* \par
simon	0:1014af42efd9	48	* The function is implemented using a 32-bit internal accumulator.
simon	0:1014af42efd9	49	* The input is represented in 1.15 format and is accumulated in a 32-bit
simon	0:1014af42efd9	50	* accumulator in 17.15 format.
simon	0:1014af42efd9	51	* There is no risk of internal overflow with this approach, and the
simon	0:1014af42efd9	52	* full precision of intermediate result is preserved.
simon	0:1014af42efd9	53	* Finally, the accumulator is saturated and truncated to yield a result of 1.15 format.
simon	0:1014af42efd9	54	*
simon	0:1014af42efd9	55	*/
simon	0:1014af42efd9	56
simon	0:1014af42efd9	57
simon	0:1014af42efd9	58	void arm_mean_q15(
simon	0:1014af42efd9	59	q15_t * pSrc,
simon	0:1014af42efd9	60	uint32_t blockSize,
simon	0:1014af42efd9	61	q15_t * pResult)
simon	0:1014af42efd9	62	{
simon	0:1014af42efd9	63	q31_t sum = 0; /* Temporary result storage */
simon	0:1014af42efd9	64	uint32_t blkCnt; /* loop counter */
simon	0:1014af42efd9	65
simon	0:1014af42efd9	66	/loop Unrolling /
simon	0:1014af42efd9	67	blkCnt = blockSize >> 2u;
simon	0:1014af42efd9	68
simon	0:1014af42efd9	69	/* First part of the processing with loop unrolling. Compute 4 outputs at a time.
simon	0:1014af42efd9	70	** a second loop below computes the remaining 1 to 3 samples. */
simon	0:1014af42efd9	71	while(blkCnt > 0u)
simon	0:1014af42efd9	72	{
simon	0:1014af42efd9	73	/* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
simon	0:1014af42efd9	74	sum += *pSrc++;
simon	0:1014af42efd9	75	sum += *pSrc++;
simon	0:1014af42efd9	76	sum += *pSrc++;
simon	0:1014af42efd9	77	sum += *pSrc++;
simon	0:1014af42efd9	78
simon	0:1014af42efd9	79	/* Decrement the loop counter */
simon	0:1014af42efd9	80	blkCnt--;
simon	0:1014af42efd9	81	}
simon	0:1014af42efd9	82
simon	0:1014af42efd9	83	/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
simon	0:1014af42efd9	84	** No loop unrolling is used. */
simon	0:1014af42efd9	85	blkCnt = blockSize % 0x4u;
simon	0:1014af42efd9	86
simon	0:1014af42efd9	87	while(blkCnt > 0u)
simon	0:1014af42efd9	88	{
simon	0:1014af42efd9	89	/* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
simon	0:1014af42efd9	90	sum += *pSrc++;
simon	0:1014af42efd9	91
simon	0:1014af42efd9	92	/* Decrement the loop counter */
simon	0:1014af42efd9	93	blkCnt--;
simon	0:1014af42efd9	94	}
simon	0:1014af42efd9	95
simon	0:1014af42efd9	96	/* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) / blockSize */
simon	0:1014af42efd9	97	/* Store the result to the destination */
simon	0:1014af42efd9	98	*pResult = (q15_t) (sum / blockSize);
simon	0:1014af42efd9	99	}
simon	0:1014af42efd9	100
simon	0:1014af42efd9	101	/**
simon	0:1014af42efd9	102	* @} end of mean group
simon	0:1014af42efd9	103	*/

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Type:	Library
Created:	10 Mar 2011
Imports:	907
Forks:	1
Commits:	3
Dependents:	5
Dependencies:	0
Followers:	35

src/Cortex-M4-M3/StatisticsFunctions/arm_mean_q15.c@0:1014af42efd9, 2011-03-10 (annotated)

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