IPPISet is slower than memset & IPPSSET

Hi,

  We tried IPPISET roi based method to set the set of portions in the image 0.

  But this is slower than memset [on entire image to 0]

  We have tried the IPPSSET and found it is more faster than memset and IPPISET.

  Is the ROI based method usually slower than non-ROI based method like IPPSSET.

  Actually we thought since we were doing selective regions in image to reset to zero using IPPISET ,it should be faster than memset and IPPSET   performed on entire image.

   But when we profile we found the IPPISET[called four time on four different small region on image] is taking more time than IPPSSET and memset.

  Can you please explain why/how this can happen?

  We were using IPP 7.0 version.

 Thanks & Regards,

Murali