Monday, 10 December 2007

Number of features grows logarithmically

The main problem in big software projects is complexity growing as the project unfolds. Generally when the main architecture is ready and the product has been started the number of architectural features grows with the size of the code. The speed of growing, though, is not constant. At the beginning it is almost linear and equal to time multiplied by team. But the longer it lasts, the bigger size of the code, the more complex is the product to develop further. From my personal experience the time spent to develop a new feature of average size increases by an exponential law. [Features are meant to be architectural but perceived in complexity from the customer point of view.] This idea gives a rule to predict milestones and practical limit of the product. For example, if the first 10 features took 4 days to develop and the second 10 new features took another 5 days to develop, then to implement 50 features will take 7 weeks and to implement 100 features 27 weeks. [Formula used is y=F*ln(kt+1). In the example above we find that k=1/16 and F=10/ln1.25]