Date: Tue, 28 Jul 2020 11:24:49 +0100 Subject: Official ARM version: v5.6.0 --- docs/DSP/html/group__variance.html | 75 +++++++++++++++++--------------------- 1 file changed, 33 insertions(+), 42 deletions(-) (limited to 'docs/DSP/html/group__variance.html') diff --git a/docs/DSP/html/group__variance.html b/docs/DSP/html/group__variance.html index f0a761a..7810a75 100644 --- a/docs/DSP/html/group__variance.html +++ b/docs/DSP/html/group__variance.html @@ -32,7 +32,7 @@ Logo

CMSIS-DSP - Version 1.5.2 + Version 1.7.0

CMSIS DSP Software Library

@@ -116,29 +116,30 @@ $(document).ready(function(){initNavTree('group__variance.html','');}); - - - - - - - - - + + + + + + + + +

Functions
void	arm_var_f32 (float32_t pSrc, uint32_t blockSize, float32_t pResult)
	Variance of the elements of a floating-point vector. More...

void	arm_var_q15 (q15_t pSrc, uint32_t blockSize, q15_t pResult)
	Variance of the elements of a Q15 vector. More...

void	arm_var_q31 (q31_t pSrc, uint32_t blockSize, q31_t pResult)
	Variance of the elements of a Q31 vector. More...

void	arm_var_f32 (const float32_t pSrc, uint32_t blockSize, float32_t pResult)
	Variance of the elements of a floating-point vector. More...

void	arm_var_q15 (const q15_t pSrc, uint32_t blockSize, q15_t pResult)
	Variance of the elements of a Q15 vector. More...

void	arm_var_q31 (const q31_t pSrc, uint32_t blockSize, q31_t pResult)
	Variance of the elements of a Q31 vector. More...

Description

Calculates the variance of the elements in the input vector. The underlying algorithm used is the direct method sometimes referred to as the two-pass method:

-  Result = sum(element - meanOfElements)^2) / numElement - 1

    where, meanOfElements = ( pSrc[0] * pSrc[0] + pSrc[1] * pSrc[1] + ... + pSrc[blockSize-1] ) / blockSize

There are separate functions for floating point, Q31, and Q15 data types.

+ Result = sum(element - meanOfElements)^2) / numElement - 1

    meanOfElements = ( pSrc[0] * pSrc[0] + pSrc[1] * pSrc[1] + ... + pSrc[blockSize-1] ) / blockSize
+

There are separate functions for floating point, Q31, and Q15 data types.

Function Documentation

- +

- + @@ -162,28 +163,24 @@ Functions

Parameters

void arm_var_f32 ( float32_t * const float32_t * pSrc,

- - - + + +

[in]	*pSrc	points to the input vector
[in]	blockSize	length of the input vector
[out]	*pResult	variance value returned here
[in]	pSrc	points to the input vector
[in]	blockSize	number of samples in input vector
[out]	pResult	variance value returned here

Returns: none.

- -

References blockSize.

- -

Referenced by main().

Returns: none

- +

- + @@ -207,28 +204,25 @@ Functions

Parameters

void arm_var_q15 ( q15_t * const q15_t * pSrc,

- - - + + +

[in]	*pSrc	points to the input vector
[in]	blockSize	length of the input vector
[out]	*pResult	variance value returned here
[in]	pSrc	points to the input vector
[in]	blockSize	number of samples in input vector
[out]	pResult	variance value returned here

Returns: none.

Scaling and Overflow Behavior:

: 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.

- -

References __SIMD32, __SMLALD(), and blockSize.

Returns: none

Scaling and Overflow Behavior: 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.

- +

- + @@ -252,17 +246,14 @@ Functions

Parameters

void arm_var_q31 ( q31_t * const q31_t * pSrc,

- - - + + +

[in]	*pSrc	points to the input vector
[in]	blockSize	length of the input vector
[out]	*pResult	variance value returned here
[in]	pSrc	points to the input vector
[in]	blockSize	number of samples in input vector
[out]	pResult	variance value returned here

Returns: none.

Scaling and Overflow Behavior:

: The function is implemented using an internal 64-bit accumulator. The input is represented in 1.31 format, which is then downshifted by 8 bits which yields 1.23, and intermediate multiplication yields a 2.46 format. The accumulator maintains full precision of the intermediate multiplication results, but provides only a 16 guard bits. 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)-8 bits, as a total of blockSize additions are performed internally. After division, internal variables should be Q18.46 Finally, the 18.46 accumulator is right shifted by 15 bits to yield a 1.31 format value.

- -

References blockSize.

Returns: none

Scaling and Overflow Behavior: The function is implemented using an internal 64-bit accumulator. The input is represented in 1.31 format, which is then downshifted by 8 bits which yields 1.23, and intermediate multiplication yields a 2.46 format. The accumulator maintains full precision of the intermediate multiplication results, but provides only a 16 guard bits. 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)-8 bits, as a total of blockSize additions are performed internally. After division, internal variables should be Q18.46 Finally, the 18.46 accumulator is right shifted by 15 bits to yield a 1.31 format value.

@@ -271,7 +262,7 @@ Functions