Atan

Computes inverse tangent of each vector element.

Syntax

IppStatus ippsAtan_32f_A11 (const Ipp32f* pSrc, Ipp32f* pDst, Ipp32s len);

IppStatus ippsAtan_32f_A21 (const Ipp32f* pSrc, Ipp32f* pDst, Ipp32s len);

IppStatus ippsAtan_32f_A24 (const Ipp32f* pSrc, Ipp32f* pDst, Ipp32s len);

IppStatus ippsAtan_64f_A26 (const Ipp64f* pSrc, Ipp64f* pDst, Ipp32s len);

IppStatus ippsAtan_64f_A50 (const Ipp64f* pSrc, Ipp64f* pDst, Ipp32s len);

IppStatus ippsAtan_64f_A53 (const Ipp64f* pSrc, Ipp64f* pDst, Ipp32s len);

IppStatus ippsAtan_32fc_A11 (const Ipp32fc* pSrc, Ipp32fc* pDst, Ipp32s len);

IppStatus ippsAtan_32fc_A21 (const Ipp32fc* pSrc, Ipp32fc* pDst, Ipp32s len);

IppStatus ippsAtan_32fc_A24 (const Ipp32fc* pSrc, Ipp32fc* pDst, Ipp32s len);

IppStatus ippsAtan_64fc_A26 (const Ipp64fc* pSrc, Ipp64fc* pDst, Ipp32s len);

IppStatus ippsAtan_64fc_A50 (const Ipp64fc* pSrc, Ipp64fc* pDst, Ipp32s len);

IppStatus ippsAtan_64fc_A53 (const Ipp64fc* pSrc, Ipp64fc* pDst, Ipp32s len);

Parameters

pSrc	Pointer to the source vector.
pDst	Pointer to the destination vector.
len	Number of elements in the vectors.

Description

The function ippsAtan is declared in the ippvm.h file. This function computes the inverse tangent of each element of pSrc, and stores the result in the corresponding element of pDst.

For single precision data:

function flavors ippsAtan_32f_A11and ippsAtan_32cf_A11 guarantee 11 correctly rounded bits of significand, or at least 3 exact decimal digits;

function flavors ippsAtan_32f_A21 and ippsAtan_32fc_A21 guarantee 21 correctly rounded bits of significand, or 4 ulps, or about 6 exact decimal digits;

function flavors ippsAtan_32f_A24 and ippsAtan_32fc_A24 guarantee 24 correctly rounded bits of significand, including the implied bit, with the maximum guaranteed error within 1 ulp.

For double precision data:

function flavors ippsAtan_64f_A26 and ippsAtan_64fc_A26 guarantee 26 correctly rounded bits of significand, or 6.7E+7 ulps, or approximately 8 exact decimal digits;

function flavors ippsAtan_64f_A50 and ippsAtan_64fc_A50 guarantee 50 correctly rounded bits of significand, or 4 ulps, or approximately 15 exact decimal digits;

function flavors ippsAtan_64f_A53 and ippsAtan_64fc_A53 guarantee 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] = atan(pSrc[n]), 0 ≤ n < len.

The example below shows how to use the function ippsAtan.

Return Values

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

Using ippsAtan Function

IppStatus ippsAtan_32f_A21_sample(void)

const Ipp32f x[4] = {0.994, 0.999, 0.223, -0.215};

Ipp32f      			y[4];

	IppStatus st = ippsAtan_32f_A21( x, y, 4 );

	printf(" ippsAtan_32f_A21:\n");

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

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

	return st;

Output results:

 ippsAtan_32f_A21:

 x = 0.994 0.999 0.223 -0.215

 y = 0.782 0.785 0.219 -0.212