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src/Cortex-M4-M3/StatisticsFunctions/arm_var_f32.c@0:1014af42efd9, 2011-03-10 (annotated)

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

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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_var_f32.c
simon	0:1014af42efd9	9	*
simon	0:1014af42efd9	10	* Description: Variance of an array of F32 type.
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	* @defgroup variance Variance
simon	0:1014af42efd9	35	*
simon	0:1014af42efd9	36	* Calculates the variance of the elements in the input vector.
simon	0:1014af42efd9	37	* The underlying algorithm is used:
simon	0:1014af42efd9	38	*
simon	0:1014af42efd9	39	* <pre>
simon	0:1014af42efd9	40	* Result = (sumOfSquares - sum<sup>2</sup> / blockSize) / (blockSize - 1)
simon	0:1014af42efd9	41	*
simon	0:1014af42efd9	42	* where, sumOfSquares = pSrc[0] * pSrc[0] + pSrc[1] * pSrc[1] + ... + pSrc[blockSize-1] * pSrc[blockSize-1]
simon	0:1014af42efd9	43	*
simon	0:1014af42efd9	44	* sum = pSrc[0] + pSrc[1] + pSrc[2] + ... + pSrc[blockSize-1]
simon	0:1014af42efd9	45	* </pre>
simon	0:1014af42efd9	46	*
simon	0:1014af42efd9	47	* There are separate functions for floating point, Q31, and Q15 data types.
simon	0:1014af42efd9	48	*/
simon	0:1014af42efd9	49
simon	0:1014af42efd9	50	/**
simon	0:1014af42efd9	51	* @addtogroup variance
simon	0:1014af42efd9	52	* @{
simon	0:1014af42efd9	53	*/
simon	0:1014af42efd9	54
simon	0:1014af42efd9	55
simon	0:1014af42efd9	56	/**
simon	0:1014af42efd9	57	* @brief Variance of the elements of a floating-point vector.
simon	0:1014af42efd9	58	* @param[in] *pSrc points to the input vector
simon	0:1014af42efd9	59	* @param[in] blockSize length of the input vector
simon	0:1014af42efd9	60	* @param[out] *pResult variance value returned here
simon	0:1014af42efd9	61	* @return none.
simon	0:1014af42efd9	62	*
simon	0:1014af42efd9	63	*/
simon	0:1014af42efd9	64
simon	0:1014af42efd9	65
simon	0:1014af42efd9	66	void arm_var_f32(
simon	0:1014af42efd9	67	float32_t * pSrc,
simon	0:1014af42efd9	68	uint32_t blockSize,
simon	0:1014af42efd9	69	float32_t * pResult)
simon	0:1014af42efd9	70	{
simon	0:1014af42efd9	71	float32_t sum = (float32_t) 0.0; /* Accumulator */
simon	0:1014af42efd9	72	float32_t meanOfSquares, mean, in, squareOfMean; /* Temporary variables */
simon	0:1014af42efd9	73	uint32_t blkCnt; /* loop counter */
simon	0:1014af42efd9	74	float32_t pIn; / Temporary pointer */
simon	0:1014af42efd9	75
simon	0:1014af42efd9	76	/* updating temporary pointer */
simon	0:1014af42efd9	77	pIn = pSrc;
simon	0:1014af42efd9	78
simon	0:1014af42efd9	79	/loop Unrolling /
simon	0:1014af42efd9	80	blkCnt = blockSize >> 2u;
simon	0:1014af42efd9	81
simon	0:1014af42efd9	82	/* First part of the processing with loop unrolling. Compute 4 outputs at a time.
simon	0:1014af42efd9	83	** a second loop below computes the remaining 1 to 3 samples. */
simon	0:1014af42efd9	84	while(blkCnt > 0u)
simon	0:1014af42efd9	85	{
simon	0:1014af42efd9	86	/* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
simon	0:1014af42efd9	87	/* Compute Sum of squares of the input samples
simon	0:1014af42efd9	88	* and then store the result in a temporary variable, sum. */
simon	0:1014af42efd9	89	in = *pSrc++;
simon	0:1014af42efd9	90	sum += in * in;
simon	0:1014af42efd9	91	in = *pSrc++;
simon	0:1014af42efd9	92	sum += in * in;
simon	0:1014af42efd9	93	in = *pSrc++;
simon	0:1014af42efd9	94	sum += in * in;
simon	0:1014af42efd9	95	in = *pSrc++;
simon	0:1014af42efd9	96	sum += in * in;
simon	0:1014af42efd9	97
simon	0:1014af42efd9	98	/* Decrement the loop counter */
simon	0:1014af42efd9	99	blkCnt--;
simon	0:1014af42efd9	100	}
simon	0:1014af42efd9	101
simon	0:1014af42efd9	102	/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
simon	0:1014af42efd9	103	** No loop unrolling is used. */
simon	0:1014af42efd9	104	blkCnt = blockSize % 0x4u;
simon	0:1014af42efd9	105
simon	0:1014af42efd9	106	while(blkCnt > 0u)
simon	0:1014af42efd9	107	{
simon	0:1014af42efd9	108	/* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
simon	0:1014af42efd9	109	/* Compute Sum of squares of the input samples
simon	0:1014af42efd9	110	* and then store the result in a temporary variable, sum. */
simon	0:1014af42efd9	111	in = *pSrc++;
simon	0:1014af42efd9	112	sum += in * in;
simon	0:1014af42efd9	113
simon	0:1014af42efd9	114	/* Decrement the loop counter */
simon	0:1014af42efd9	115	blkCnt--;
simon	0:1014af42efd9	116	}
simon	0:1014af42efd9	117
simon	0:1014af42efd9	118	/* Compute Mean of squares of the input samples
simon	0:1014af42efd9	119	* and then store the result in a temporary variable, meanOfSquares. */
simon	0:1014af42efd9	120	meanOfSquares = sum / ((float32_t) blockSize - 1.0f);
simon	0:1014af42efd9	121
simon	0:1014af42efd9	122	/* Reset the accumulator */
simon	0:1014af42efd9	123	sum = 0.0f;
simon	0:1014af42efd9	124
simon	0:1014af42efd9	125	/loop Unrolling /
simon	0:1014af42efd9	126	blkCnt = blockSize >> 2u;
simon	0:1014af42efd9	127
simon	0:1014af42efd9	128	/* Reset the input working pointer */
simon	0:1014af42efd9	129	pSrc = pIn;
simon	0:1014af42efd9	130
simon	0:1014af42efd9	131	/* First part of the processing with loop unrolling. Compute 4 outputs at a time.
simon	0:1014af42efd9	132	** a second loop below computes the remaining 1 to 3 samples. */
simon	0:1014af42efd9	133	while(blkCnt > 0u)
simon	0:1014af42efd9	134	{
simon	0:1014af42efd9	135	/* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
simon	0:1014af42efd9	136	/* Compute sum of all input values and then store the result in a temporary variable, sum. */
simon	0:1014af42efd9	137	sum += *pSrc++;
simon	0:1014af42efd9	138	sum += *pSrc++;
simon	0:1014af42efd9	139	sum += *pSrc++;
simon	0:1014af42efd9	140	sum += *pSrc++;
simon	0:1014af42efd9	141
simon	0:1014af42efd9	142	/* Decrement the loop counter */
simon	0:1014af42efd9	143	blkCnt--;
simon	0:1014af42efd9	144	}
simon	0:1014af42efd9	145
simon	0:1014af42efd9	146	/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
simon	0:1014af42efd9	147	** No loop unrolling is used. */
simon	0:1014af42efd9	148	blkCnt = blockSize % 0x4u;
simon	0:1014af42efd9	149
simon	0:1014af42efd9	150	while(blkCnt > 0u)
simon	0:1014af42efd9	151	{
simon	0:1014af42efd9	152	/* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
simon	0:1014af42efd9	153	/* Compute sum of all input values and then store the result in a temporary variable, sum. */
simon	0:1014af42efd9	154	sum += *pSrc++;
simon	0:1014af42efd9	155
simon	0:1014af42efd9	156	/* Decrement the loop counter */
simon	0:1014af42efd9	157	blkCnt--;
simon	0:1014af42efd9	158	}
simon	0:1014af42efd9	159	/* Compute mean of all input values */
simon	0:1014af42efd9	160	mean = sum / (float32_t) blockSize;
simon	0:1014af42efd9	161
simon	0:1014af42efd9	162	/* Compute square of mean */
simon	0:1014af42efd9	163	squareOfMean = (mean * mean) * (((float32_t) blockSize) /
simon	0:1014af42efd9	164	((float32_t) blockSize - 1.0f));
simon	0:1014af42efd9	165
simon	0:1014af42efd9	166	/* Compute variance and then store the result to the destination */
simon	0:1014af42efd9	167	*pResult = meanOfSquares - squareOfMean;
simon	0:1014af42efd9	168
simon	0:1014af42efd9	169	}
simon	0:1014af42efd9	170
simon	0:1014af42efd9	171	/**
simon	0:1014af42efd9	172	* @} end of variance group
simon	0:1014af42efd9	173	*/

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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_var_f32.c@0:1014af42efd9, 2011-03-10 (annotated)

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