A model for correlated failures in N-version programming

The multi-version programming technique is a method to increase the reliability of safety critical software. In this technique a number of versions are developed and a voting scheme is used before a final result is provided. In the analysis of this type of systems, a common assumption is the independence of the different versions. However, the different versions are usually interdependent and failures are correlated due to the nature of the product design and development. One version may fail simultaneously with another version because of a common cause. In this paper, a model for these dependent failures is developed and studied. Using the developed model, a reliability function can be easily computed. A method is also proposed to estimate the parameters of the model. Finally, as an application of the developed model, an optimal testing resource allocation problem is formulated and a genetic algorithm is presented to solve the problem.