Automating the Addition of Fault-Tolerance

Abstract

In this paper, we focus on automating the transformation of a given fault-intolerant program into a fault-tolerant program. We show how such a transformation can be done for three levels of fault-tolerance properties, failsafe, nonmasking and masking. For the high atomicity model where the program can read all the variables and write all the variables in one atomic step, we show that all three transformations can be performed in polynomial time in the state space of the fault-intolerant program. For the low atomicity model where restrictions are imposed on the ability of programs to read and write variables, we show that all three transformations can be performed in exponential time in the state space of the fault-intolerant program. We also show that the the problem of adding masking fault-tolerance is NP-hard and, hence, exponential complexity is inevitable unless P =NP.

Email: sandeep@cse.msu.edu, nish@cis.ohio-state.edu. Web: http://www.cse.msu. edu/~sandeep, http://www.cis.ohio-state.edu/~anish. Tel: +1-517-355-2387. Arora is currently on sabbatical leave at Microsoft Research. This work was partially sponsored by NSA Grant MDA904-96-1-0111, NSF Grant NSF-CCR-9972368, an Ameritech Faculty Fellowship, a grant from Microsoft Research, and a grant from Michigan State University.