Square Root

Functions
arm_status	arm_sqrt_q15 (q15_t in, q15_t *pOut)
	Q15 square root function.
arm_status	arm_sqrt_q31 (q31_t in, q31_t *pOut)
	Q31 square root function.
static __INLINE arm_status	arm_sqrt_f32 (float32_t in, float32_t *pOut)
	Floating-point square root function.

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]

Function Documentation

static __INLINE arm_status arm_sqrt_f32 ( float32_t  in, float32_t *  pOut  )

static

Parameters

[in]	in	input value.
[out]	pOut	square root of input value.

Returns

The function returns ARM_MATH_SUCCESS if input value is positive value or ARM_MATH_ARGUMENT_ERROR if in is negative value and returns zero output for negative values.

References ARM_MATH_ARGUMENT_ERROR, and ARM_MATH_SUCCESS.

Referenced by arm_cmplx_mag_f32(), arm_rms_f32(), and arm_std_f32().

arm_status arm_sqrt_q15	(	q15_t	in,
		q15_t *	pOut
	)

Parameters

[in]	in	input value. The range of the input value is [0 +1) or 0x0000 to 0x7FFF.
[out]	*pOut	square root of input value.

Returns

The function returns ARM_MATH_SUCCESS if the input value is positive and ARM_MATH_ARGUMENT_ERROR if the input is negative. For negative inputs, the function returns *pOut = 0.

Parameters

[in]	in	input value. The range of the input value is [0 +1) or 0x0000 to 0x7FFF.
[out]	pOut	square root of input value.

Returns

The function returns ARM_MATH_SUCCESS if input value is positive value or ARM_MATH_ARGUMENT_ERROR if in is negative value and returns zero output for negative values.

References ARM_MATH_ARGUMENT_ERROR, and ARM_MATH_SUCCESS.

Referenced by arm_cmplx_mag_q15(), arm_rms_q15(), and arm_std_q15().

arm_status arm_sqrt_q31	(	q31_t	in,
		q31_t *	pOut
	)

Parameters

[in]	in	input value. The range of the input value is [0 +1) or 0x00000000 to 0x7FFFFFFF.
[out]	*pOut	square root of input value.

Returns

The function returns ARM_MATH_SUCCESS if the input value is positive and ARM_MATH_ARGUMENT_ERROR if the input is negative. For negative inputs, the function returns *pOut = 0.

Parameters

[in]	in	input value. The range of the input value is [0 +1) or 0x00000000 to 0x7FFFFFFF.
[out]	pOut	square root of input value.

Returns

The function returns ARM_MATH_SUCCESS if input value is positive value or ARM_MATH_ARGUMENT_ERROR if in is negative value and returns zero output for negative values.

References ARM_MATH_ARGUMENT_ERROR, and ARM_MATH_SUCCESS.

Referenced by arm_cmplx_mag_q31(), arm_rms_q31(), and arm_std_q31().