Any IPP primitive for de-spread function

[rohitspandey]

HI,

Is there are any despread function?

I have implemented this in C. Is there any IPP function

for (sym = 0; sym < N_corr; sym++)

{

sum = 0.0f;

for (chip = 0; chip < sf; chip++)

{

sum += (*pSrc++) * (*pW++); //

}

*pDest++ = sum; //

pW -= sf; //

}

Regards

Rohit

[Chao_Y_Intel]

Rohit,

The inner loop looks to a dot products, and hot spot of the code

for (chip = 0; chip < sf; chip++){

sum += (*pSrc++) * (*pW++); //

}

If sf is large, the code could be replace with ippsDotProd_ function.

Thanks,C
Chao

[igorastakhov]

I see only 2 possible variants based on the currently available IPP functionality:
1) already mentioned by Chao:

for (sym = 0; sym < N_corr; sym++){

Ipp32f sum;

ippsDotProd_32f( pSrc, pW, sf, ∑ );
*pDest++ = sum; //
pSrc += sf;
}
2) with temp buf of size sf:
Ipp32f sum;
for( sym = 0; sym < N_corr; sym += sf ){
ippsMul_32f( pSrc, pW, pBuf, sf );
pSrc += sf;
ippsSum_32f( pBuf, sf, ∑, ippAlgHintFast );
*pDest++ = sum;
}
3) based on AddProduct function - guess not so efficient

and I think that the 1st one should be the most efficient in case of reasonable sf, otherwise there is no alternative for C code compiled with Intel compiler - but for efficien code generation (vectorization) you should re-write your code with arrays and indexes and use "ivdep" pragma.

Regards,
Igor

[rohitspandey]

Hi,

Thanks for the help. The performance of dotproduct is good for significant sf sizes compared to C.

Regards
Rohit