Meaning of "Step" in ippsSVD_64f_D2?

[lkeene]

Hello all,

what is the meaning of the "step" term in the ippsSVD_64f_D2(...) function documentation? I'm trying to perform the SVD of a 3x3 matrix (passed as a vector[3x3] to the function). Is the step just 3 in my case? Or is it referring to the number of bytes per row...or something else? For example, from the docs:

"pSrcA -> Pointer to the input vector A[height*step]."

Thanks in advance.

-L

[Vladimir_Dudnik]

According documentation step is Row step in the vector pSrcA, pSrcDstA, or pDstV. It means distance in bytes between two adjacent rows.

Regards,
Vladimir

[Ying_H_Intel]

Quoting - lkeene

Hello all,

what is the meaning of the "step" term in the ippsSVD_64f_D2(...) function documentation? I'm trying to perform the SVD of a 3x3 matrix (passed as a vector[3x3] to the function). Is the step just 3 in my case? Or is it referring to the number of bytes per row...or something else? For example, from the docs:

"pSrcA -> Pointer to the input vector A[height*step]."

Thanks in advance.

-L

Hi
Yes, the step is 3 in your case. For square matrix, it is height=step=width.

Here is one sample

#include "stdafx.h"
#include "ipp.h"
int _tmain(int argc, _TCHAR* argv[])
{
const IppLibraryVersion* ippVersion = ippiGetLibVersion();

printf("IPP: [ %s %s ]", ippVersion->Name, ippVersion->Version);

//Ipp64f pSrcA[3*2]=
//{9, 4,
//6, 8,
//2, 7};

Ipp64f pSrcA[4*8] =
{3, 3, 3, 3, 3, 8, 8, 8,
3, 2, 1, 2, 3, 8, 8, 8,
3, 2, 1, 2, 3, 8, 8, 8,
3, 3, 3, 3, 3, 8, 8, 8};

const int height=4;
const int width=8;
const int step=8;
int nIter=10;

Ipp64f pDstU[height*step];
Ipp64f pDstW[width];
Ipp64f pDstV[width*step];

IppStatus ret=ippsSVD_64f_D2(pSrcA,pDstU, height,pDstW, pDstV, width, step, nIter);

printf("n%d : %sn", ret, ippGetStatusString(ret));

printf("n the result in U n");
for ( int y = 0; y < height; y++ )
{printf("n");
for ( int x = 0; x < step; x++ )
printf("%3.2f ", pDstU[(y * step) + x]);
}

printf("nn the result in W n");
for ( int y = 0; y < width; y++ )
printf("%3.2f ", pDstW);

printf("nn the result in V n");
for ( int y = 0; y < width; y++ )
{
printf("n");
for ( int x = 0; x < step; x++ )
printf("%3.2f ", pDstV[(y * step) + x]);
}

return 0;
}

Regards,
Ying