Unexpected behavior while using IPP with sample application

[Mohammad_M_1]

I am new to IPP and am trying to compile one of the sample applications that are freely available to the users, the string processing (pattern matching) application available at:

http://software.intel.com/en-us/articles/code-samples-for-intel-integrated-performance-primitives-intel-ipp-library-71

My machine has an intel CORE i3 processor - 2 cores and 2 threads for each core. I am using a relatively large file as an input to the pattern matching applicaton for test purposes. What baffles me is that the code runs faster when I have only one logical processor active vs 4 processors (those are the only situations I ran the test under). The way I disable cores is by using msconfig.exe. Could somebody please tell me why this is happening?

The OS is Windows 7 and code is compiled using Intel Parallel Studio 2011.

[Ying_H_Intel]

Hi Mohammad I supposed you are checking the ippgrep sample, right? You may know that not all IPP functions and IPP sample are multi-threaded. As most of ipp string porcessing functions are not threaded and IPP grep sample is not threaded. So there is no much different when run it with 1 or 2 or 4 threading. You may check a list of the threaded primitives in the IPP library is provided in the ThreadedFunctionsList.txt file located in the library’s doc directory and the article talking about IPP and threading : http://software.intel.com/en-us/articles/openmp-and-the-intel-ipp-library/ Best Regards, Ying http://software.intel.com/en-us/articles/openmp-and-the-intel-ipp-library/

[SergeyKostrov]

I'd like to add that a list of threaded IPP functions ThreadedFunctionsList.txt is located in a folder: [ ICCInstallDir ]\Composer XE\Documentation\en_US\Ipp If you don't have that file please let me know and I'll upload it for you.