gprof_compare is a little utility which can help you profile differences in
runtime between multiple runs of the same application.  First, use gprof to
obtain profiling information for the software in question.  Now, make a change
to the software or input, run gprof again, and compare the profiling traces
using gprof_compare:

  % gprof_compare gmon1.out gmon2.out

If you sort the output using "sort -n -k 1" then you'll be able to find the
functions which changed the most in terms of the number of calls.  This is very
useful in finding scaling issues in data-intensive code, and verifying that
performance-related changes do what you want them to do, and only what you want
them to do.

Erik Garrison <erik@hypervolu.me>