topic SIMD for calculating checksum in Software Tuning, Performance Optimization & Platform Monitoring

SIMD for calculating checksum

zoolii — Tue, 20 Mar 2012 09:26:58 GMT

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

SIMD for calculating checksum

SergeyKostrov — Fri, 23 Mar 2012 12:54:36 GMT

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

SIMD for calculating checksum

zoolii — Mon, 26 Mar 2012 05:04:27 GMT

Hi Sergy,

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

Regards

Zooli

SIMD for calculating checksum

SergeyKostrov — Mon, 26 Mar 2012 13:05:10 GMT

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

Best regards,
Sergey

SIMD for calculating checksum

SergeyKostrov — Mon, 26 Mar 2012 13:09:32 GMT

Please take a look at anarticle:

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

SIMD for calculating checksum

TimP — Mon, 26 Mar 2012 22:21:41 GMT

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