SIMD for calculating checksum

[zoolii]

Hi Experts,

Can we optimize following checksum calculation using SIMD somehow ?


for(int i = 0 ; i < buffSize_ ; i++) {
hashVal = (hashVal<<5) + hashVal + pBuffer_;
}



Thank you
Zooli

[SergeyKostrov]

Quoting zoolii

Hi Experts,

Can we optimize following checksum calculation using SIMD somehow ?

for(int i = 0 ; i < buffSize_ ; i++) {
hashVal = (hashVal<<5) + hashVal + pBuffer_;
}

Thank you
Zooli

Yes, with and without SSE. Also, you didn't specifytypes of'hashVal' and'pBuffer_'variables.

Best regards,
Sergey

[zoolii]

Hi Sergy,

Thanks for the reply. hashVal can be an unsigned int or long . pBuffer_ is an unsigned char array.

Regards

Zooli

[SergeyKostrov]

You need to consider a set of SSE3 instructions for a horizontal addition.

Best regards,
Sergey

[SergeyKostrov]

Please take a look at anarticle:

http://software.intel.com/en-us/articles/implement-a-horizontal-addsubtract-with-sse3-instructions/

[TimP]

If the array is at all large, the vector sum reductions implemented by the compilers (nearly any compiler other than MSVC) may be superior.