OpenMP Threading and Intel IPP
The low-level primitives within the IPP library generally represent basic atomic operations. This limits threading within the library to ~15-20% of the primitives. Intel OpenMP is used to implement internal threading and is enabled, by default, when you use one of the multi-threaded variants of the library. Multi-threaded versions of the library are only supported on Linux, Windows, and Mac OS X.
Introduction to Threading in IPP