Intel has a product called the Integrated Performance Primitives (IPP) library (IPP). This library is essentially a toolbox of high-performance kernels for handling multimedia and other processor-intensive operations in a manner that makes extensive use of the detailed architecture of their processors (and, to a lesser degree, other manufacturers' processors that have a similar architecture).
As discussed in Chapter 1, OpenCV enjoys a close relationship with IPP, both at a software level and at an organizational level inside of the company. As a result, OpenCV is designed to automatically[37] recognize the presence of the IPP library and to automatically "swap out" the lower-performance implementations of many core functionalities for their higher-performance counterparts in IPP. The IPP library allows OpenCV to take advantage of performance opportunities that arrive from SIMD instructions in a single processor as well as from modern multicore architectures.
With these basics in hand, we can perform a wide variety of basic tasks. Moving onward through the text, we will look at many more sophisticated capabilities of OpenCV, almost all of which are built on these routines. It should be no surprise that image processing—which often requires doing the same thing to a whole lot of data, much of which is completely parallel—would realize a great benefit from any code that allows it to take advantage of parallel execution units of any form (MMX, SSE, SSE2, etc.).
The way to check and make sure that IPP is installed and working correctly is with the function
cvGetModuleInfo(), shown in Example 3-20. This function will identify both the
version of OpenCV you are currently running and the version and identity of any add-in
modules.
Example 3-20. Using cvGetModuleInfo() to check for IPP
char* libraries; char* modules; cvGetModuleInfo( 0, (const char**) &libraries, (const char**) &modules ); printf(“Libraries: %s\nModules: %s\n”, libraries, modules );
The code in Example 3-20 will generate text strings which describe the installed libraries and modules. The output might look like this:
Libraries cxcore: 1.0.0 Modules: ippcv20.dll, ippi20.dll, ipps20.dll, ippvm20.dll
The modules listed in this output are the IPP modules used by OpenCV. Those modules
are themselves actually proxies for even lower-level CPU-specific libraries. The details
of how it all works are well beyond the scope of this book, but if you see the IPP
libraries in the Modules string then you can be pretty
confident that everything is working as expected. Of course, you could use this
information to verify that IPP is running correctly on your own system. You might also use
it to check for IPP on a machine on which your finished software is installed, perhaps
then making some dynamic adjustments depending on whether IPP is available.
[37] The one prerequisite to this automatic recognition is that the binary directory of IPP must be in the system path. So on a Windows system, for example, if you have IPP in C:/Program Files/Intel/IPP then you want to ensure that C:/Program Files/Intel/IPP/bin is in your system path.