Atan2

Computes four-quadrant inverse tangent of elements of two vectors.

Syntax

IppStatus ippsAtan2_32f_A11 (const Ipp32f* pSrc1, const Ipp32f* pSrc2, Ipp32f* pDst, Ipp32s len);

IppStatus ippsAtan2_32f_A21 (const Ipp32f* pSrc1, const Ipp32f* pSrc2, Ipp32f* pDst, Ipp32s len);

IppStatus ippsAtan2_32f_A24 (const Ipp32f* pSrc1, const Ipp32f* pSrc2, Ipp32f* pDst, Ipp32s len);

IppStatus ippsAtan2_64f_A26 (const Ipp64f* pSrc1, const Ipp64f* pSrc2, Ipp64f* pDst, Ipp32s len);

IppStatus ippsAtan2_64f_A50 (const Ipp64f* pSrc1, const Ipp64f* pSrc2, Ipp64f* pDst, Ipp32s len);

IppStatus ippsAtan2_64f_A53 (const Ipp64f* pSrc1, const Ipp64f* pSrc2, Ipp64f* pDst, Ipp32s len);

Parameters

pSrc1	Pointer to the first source vector.
pSrc2	Pointer to the second source vector.
pDst	Pointer to the destination vector.
len	Number of elements in the vectors.

Description

The function ippsAtan2 is declared in the ippvm.h file. This function computes the angle between the X axis and the line from the origin to the point (X,Y), for each element of pSrc1 as a Y (the ordinate) and corresponding element of pSrc2 as an X (the abscissa), and stores the result in the corresponding element of pDst. The result angle varies from - π to + π.

For single precision data:

function flavor ippsAtan2_32f_A11 guarantees 11 correctly rounded bits of significand, or at least 3 exact decimal digits;

function flavor ippsAtan2_32f_A21 guarantees 21 correctly rounded bits of significand, or 4 ulps, or about 6 exact decimal digits;

function flavor ippsAtan2_32f_A24 guarantees 24 correctly rounded bits of significand, including the implied bit, with the maximum guaranteed error within 1 ulp.

For double precision data:

function flavor ippsAtan2_64f_A26 guarantees 26 correctly rounded bits of significand, or 6.7E+7 ulps, or approximately 8 exact decimal digits;

function flavor ippsAtan2_64f_A50 guarantees 50 correctly rounded bits of significand, or 4 ulps, or approximately 15 exact decimal digits;

function flavor ippsAtan2_64f_A53 guarantees 53 correctly rounded bits of significand, including the implied bit, with the maximum guaranteed error within 1 ulp.

The computation is performed as follows:

pDst[n] = atan2(pSrc1[n], pSrc2[n]), 0 ≤ n < len.

The example below shows how to use the function ippsAtan2.

Return Values

ippStsNoErr	Indicates no error.
ippStsNullPtrErr	Indicates an error when pSrc1, pSrc2 or pDst pointer is NULL.
ippStsSizeErr	Indicates an error when len is less than or equal to 0.

Using ippsAtan2 Function

IppStatus ippsAtan2_32f_A21_sample(void)

const Ipp32f x1[4] = {1.492, 1.700, 1.147, 1.142};

const Ipp32f x2[4] = {1.064, 1.505, 1.950, 1.905};

Ipp32f      			y[4];

	IppStatus st = ippsAtan2_32f_A21( x1, x2, y, 4 );

	printf(" ippsAtan2_32f_A21:\n");

	printf(" x1 = %.3f %.3f %.3f %.3f \n", x1[0], x1[1], x1[2], x1[3]);

	printf(" x2 = %.3f %.3f %.3f %.3f \n", x2[0], x2[1], x2[2], x2[3]);

	printf(" y  = %.3f %.3f %.3f %.3f \n", y[0],  y[1],  y[2],  y[3]);

	return st;

Output results:

 ippsAtan2_32f_A21:

 x1 = 1.492 1.700 1.147 1.142

 x2 = 1.064 1.505 1.950 1.905

 y  = 0.951 0.846 0.532 0.540