The host application starts by parsing command line arguments. Following are the command-line options provided by the host that takes the input image and uses OpenCV (in source file src/host.cpp):
CmdLineParser parser;
parser.addSwitch("--nruns", "-n", "Number of times the image is processed", "1");
parser.addSwitch("--fpga", "-x", "FPGA binary (xclbin) file to use");
parser.addSwitch("--input", "-i", "Input image file");
parser.addSwitch("--filter", "-f", "Filter type (0-6)", "0");
parser.addSwitch("--maxreqs", "-r", "Maximum number of outstanding requests", "3");
parser.addSwitch("--compare", "-c", "Compare FPGA and SW performance", "false", true);
The host_randomized.cpp file has all those options, and adds width and height options:
parser.addSwitch("--width", "-w", "Image width", "1920");
parser.addSwitch("--height", "-h", "Image height", "1080");
Different options can be used to launch the application and for performance measurements. In this lab, you will set most of these command-line inputs to the application using a makefile, make_options.mk in the top-level directory. This file lets you set most of these options.
After parsing the command-line options, the host application creates an OpenCL context, reads and loads the .xclbin, and creates a command queue with out-of-order execution and profiling enabled. After that, memory allocation is done, and the input image is read (or randomly generated).
After the setup is complete, the application creates a Filter2DDispatcher object and uses it to dispatch filtering requests on several images. Timers are used to capture execution time measurements for both software and hardware execution. Finally, the host application prints the summary of performance results. Most of the heavy lifting is done by Filter2DDispatcher and Filter2DRequest. These classes manage and coordinate the execution of filtering operations on multiple compute units. Both versions of the host application are based on these classes.