Chronograph data structure adds a measure field
to an existing Haskell expression. This field will be the
time necessary to evaluate the expression using an
arbitrary evaluation strategy (WHNF by default).
Chronograph preserves laziness, so that the work of performing the evaluation is only done after the result is demanded.
If you want to benchmark your program, you should look to other packages like Criterion that perform statistical analysis of your results so you can determine how reliable they are. Chronograph just takes measurements, leaving the interpretation entirely to you.