TY  - GEN
CY  - Los Angeles, California, USA
KW  - cs.PL
KW  -  cs.PL
KW  -  cs.LO
A1  - McIver, A
A1  - Morgan, C
A1  - Kaminski, BL
A1  - Katoen, J-P
ID  - discovery10089705
N2  - An important question for a probabilistic program is whether the probability mass of all its diverging runs is zero, that is that it terminates "almost surely". Proving that can be hard, and this paper presents a new method for doing so; it is expressed in a program logic, and so applies directly to source code. The programs may contain both probabilistic- and demonic choice, and the probabilistic choices may depend on the current state. As do other researchers, we use variant functions (a.k.a. "super-martingales") that are real-valued and probabilistically might decrease on each loop iteration; but our key innovation is that the amount as well as the probability of the decrease are parametric. We prove the soundness of the new rule, indicate where its applicability goes beyond existing rules, and explain its connection to classical results on denumerable (non-demonic) Markov chains.
PB  - ACM
UR  - https://doi.org/10.1145/3158121
N1  - This version is the author accepted manuscript. For information on re-use, please refer to the publisher?s terms and conditions.
TI  - A New Proof Rule for Almost-Sure Termination
Y1  - 2018/01//
AV  - public
ER  -