InvSqrt

Computes inverse square root of each vector element.

Syntax

IppStatus ippsInvSqrt_32f_A11 (const Ipp32f* pSrc, Ipp32f* pDst, Ipp32s len);

IppStatus ippsInvSqrt_32f_A21 (const Ipp32f* pSrc, Ipp32f* pDst, Ipp32s len);

IppStatus ippsInvSqrt_32f_A24 (const Ipp32f* pSrc, Ipp32f* pDst, Ipp32s len);

IppStatus ippsInvSqrt_64f_A26 (const Ipp64f* pSrc, Ipp64f* pDst, Ipp32s len);

IppStatus ippsInvSqrt_64f_A50 (const Ipp64f* pSrc, Ipp64f* pDst, Ipp32s len);

IppStatus ippsInvSqrt_64f_A53 (const Ipp64f* pSrc, Ipp64f* 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 ippsInvSqrt is declared in the ippvm.h file. This function computes inverse square root of each element of pSrc and stores the result in the corresponding element of pDst.

For single precision data:

function flavor ippsInvSqrt_32f_A11 guarantees 11 correctly rounded bits of significand, or at least 3 exact decimal digits;

function flavor ippsInvSqrt_32f_A21 guarantees 21 correctly rounded bits of significand, or 4 ulps, or about 6 exact decimal digits;

function flavor ippsInvSqrt_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 ippsInvSqrt_64f_A26 guarantees 26 correctly rounded bits of significand, or 6.7E+7 ulps, or approximately 8 exact decimal digits;

function flavor ippsInvSqrt_64f_A50 guarantees 50 correctly rounded bits of significand, or 4 ulps, or approximately 15 exact decimal digits;

function flavor ippsInvSqrt_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] = (pSrc[n])^-1/2, 0 ≤ n < len.

The example below shows how to use the function ippsInvSqrt.

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.
IppStsDomain	Indicates a warning that the argument is out of the function domain, that is, at least one of the elements of pSrc is less than 0.
IppStsSingularity	Indicates a warning that the argument is the singularity point, that is, at least one of the elements of pSrc is equal to 0.

Using ippsInvSqrt Function

IppStatus ippsInvSqrt_32f_A21_sample(void)

const Ipp32f x[4] = {7105.043, 5135.398, 3040.018, 149.944};

Ipp32f      	y[4];

	IppStatus st = ippsInvSqrt_32f_A21( x, y, 4 );

	printf(" ippsInvSqrt_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:

 ippsInvSqrt_32f_A21:

 x = 7105.043 5135.398 3040.018 149.944

 y = 0.012 0.014 0.018 0.082