A binary integer programming solution for optimal reliability of computer relaying software incorporating redundancy

Software reliability assessment is an area of prime importance of today, more so since computers have pervaded to practically all aspects of our lives. Moreover many software based commercial and governmental systems require very high mission reliability. To meet this, both the hardware as well as the software has to be extremely reliable. Software reliability is known to improve with the amount of testing efforts invested, which in turn leverages the cost of software development and in turn system cost. Constructing systems employing redundant inferior units that are relatively cheap is a well known alternative. Using the N-version programming paradigm, the same can be applied to software, but the cost factor becomes a major issue. The degree of redundancy employed affects reliability favorably, while increasing the cost of software design and development. In this paper, an approach to enumerate the optimal redundancy for software systems has been explored and a binary integer programming solution for the same has been presented. The methodology has been applied to the case study of a computer relay software that is employed for fault handling in power system transmission lines.