On the Variability of AI-based Software Systems Due to Environment Configurations

[Context] Nowadays, many software systems include Artificial Intelligence (AI) components and changes in the development environment have been known to induce variability in an AI-based system. [Objective] However, how an environment configuration impacts the variability of these systems is yet to be explored. Understanding and quantifying the degree of variability due to such configurations can help practitioners decide the best environment configuration for the most stable AI products. [Method] To achieve this goal, we performed experiments with eight different combinations of three key environment variables (operating system, Python version, and CPU architecture) on 30 open-source AI-based systems using the Travis CI platform. We evaluate variability using three metrics: the output of an AI component like an ML model (performance), the time required to build and run a system (processing time), and the cost associated with building and running a system (expense). [Results] Our results indicate that variability exists in all three metrics; however, it is observed more frequently with respect to processing time and expense than performance. For example, between Linux and MacOS, variabilities are observed in 23%, 96.67%, and 100% of the studied projects in performance, processing time, and expense, respectively. [Conclusion] Our findings underscore the importance of identifying the optimal combination of configuration settings to mitigate performance drops and reduce retraining time and cost before deploying an AI-based system.