It is apropriate to have initilization code in your benchmarking routines. Having initilization code will impact the absolute performance of the code by its added overhead. However, when you use Benchmark/timethere you are looking to determine the relative performance of a piece of code. As long as you use the same initilization routine in all pieces of code being benchmarked your results will be valid and useful. If you really want to knoe the absolute performance, you can also run a dummy example along with your real code that contains only the initilization routine and you can factor out the initilization routine's effect when analyzing the results.