Program profiler Find out what function is causing the bottleneck in your program. Understanding the profiler The profiler is a tool built into the runtime system that allows you to know where your program spends processing time, and which function calls which function. Syntax of the program profiler The program profiler is enabled by using the -p option of fglrun. Profiler output: Flat profile The flat profile shows a summary of the functions called during the program execution. Profiler output: Call graph The profiler call graph provides detailed function call information. Example Program profiler example.