Square Root

Collaboration diagram for Square Root:

Macros
#define	F2Q(f)   ((int)((f) * 0x8000))
	Q15 square root function. More...

Functions
static tpt_status	tpt_sqrt_f32 (f32_t *aOut, f32_t aIn)
	floating-point square root function. More...
tpt_status	tpt_sqrt_q15 (q15_t *aOut, q15_t aIn)
	Q15 square root function. More...
tpt_status	tpt_sqrt_q31 (q31_t *aOut, q31_t aIn)
	Q31 square root function. More...
void	tpt_vlog_q31 (q31_t *aOutData, const q31_t *aInData, uint32_t aCount)
	q31 vector of log values. More...

Variables
static const q3_28_t	sqrt_initial_lut_q31 [24]

Detailed Description

Computes the square root of a number. There are separate functions for Q15, Q31, and floating-point data types. The square root function is computed using the Newton-Raphson algorithm. This is an iterative algorithm of the form:

    x1 = x0 - f(x0)/f'(x0)
  

where x1 is the current estimate, x0 is the previous estimate, and f'(x0) is the derivative of f() evaluated at x0. For the square root function, the algorithm reduces to:

    x0 = in/2               [initial guess]
    x1 = 1/2 * (x0 + in/x0) [each iteration]
  

Macro Definition Documentation

F2Q

#define F2Q

(

f

)

((int)((f) * 0x8000))

Q15 square root function.

Parameters

[out]	aOut	points to square root of input value.
[in]	aIn	input value. The range of the input value is [0 1)

Returns

execution status

• TPT_MATH_SUCCESS : input value is not negative.
• TPT_MATH_ARGUMENT_ERROR : input value is negative. *aOut is set to 0

Function Documentation

tpt_sqrt_f32()

static tpt_status tpt_sqrt_f32 ( f32_t *  aOut, f32_t  aIn  )

inlinestatic

floating-point square root function.

Parameters

[out]	aOut	points to square root of input value.
[in]	aIn	input value.

Returns

execution status

• TPT_MATH_SUCCESS : input value is not negative.
• TPT_MATH_ARGUMENT_ERROR : input value is negative. *aOut is set to 0

tpt_sqrt_q15()

tpt_status tpt_sqrt_q15	(	q15_t *	aOut,
		q15_t	aIn
	)

Q15 square root function.

Parameters

[out]	aOut	points to square root of input value.
[in]	aIn	input value. The range of the input value is [0 1)

Returns

execution status

• TPT_MATH_SUCCESS : input value is not negative.
• TPT_MATH_ARGUMENT_ERROR : input value is negative. *aOut is set to 0

tpt_sqrt_q31()

tpt_status tpt_sqrt_q31	(	q31_t *	aOut,
		q31_t	aIn
	)

Q31 square root function.

Parameters

[out]	aOut	points to square root of input value.
[in]	aIn	input value. The range of the input value is [0 1)

Returns

execution status

• TPT_MATH_SUCCESS : input value is not negative.
• TPT_MATH_ARGUMENT_ERROR : input value is negative. *aOut is set to 0

tpt_vlog_q31()

void tpt_vlog_q31	(	q31_t *	aOutData,
		const q31_t *	aInData,
		uint32_t	aCount
	)

q31 vector of log values.

Parameters

[in]	pSrc	points to the input vector in q31
[out]	pDst	points to the output vector in q5.26
[in]	blockSize	number of samples in each vector

Returns

none

Variable Documentation

sqrt_initial_lut_q31

const q3_28_t sqrt_initial_lut_q31[24]

static

Initial value:

= {
    536870912, 506166750, 480191942, 457845052, 438353264, 421156193,
    405836263, 392075079, 379625062, 368290407, 357913941, 348367849,
    339546978, 331363921, 323745341, 316629190, 309962566, 303700050,
    297802400, 292235509, 286969573, 281978417, 277238947, 272730696}