For this example we consider parallel computing. It is well known that the order of the operands in a computation can have significant impact upon the end result. See  for a discussion of floating-point summations. A particularly computational intensive segment of code might be rewritten to run in parallel. If the end results of the sequential and parallel codes differ one might wonder if this is the result of a coding error or of performing the computations in a different order. In this setting the comparative debugging can be used to determine the magnitudeand the first instance where the codes produce different results.
View example of parallel summation , or .