Because data is always summarized at breakpoints in the code, you can set breakpoints at any location at which you want to summarize collected data.
If your application is compiled using the -g option, you can set breakpoints in those specific areas of the code pertaining to the information you want to collect. The breakpoints can be set at the beginning or end of a function, or on any line of code.
If the application is compiled with the -O option, you can set breakpoints on functions, but not on specific source-code lines.