Publication details

Runtime analysis of probabilistic programs with unbounded recursion

Authors

BRÁZDIL Tomáš KIEFER Stefan KUČERA Antonín HUTAŘOVÁ VAŘEKOVÁ Ivana

Year of publication 2015
Type Article in Periodical
Magazine / Source Journal of Computer and System Sciences
MU Faculty or unit

Faculty of Informatics

Citation
Doi http://dx.doi.org/10.1016/j.jcss.2014.06.005
Field Informatics
Keywords pushdown automata; recursion
Description We study the runtime in probabilistic programs with unbounded recursion. As underlying formal model for such programs we use probabilistic pushdown automata (pPDAs) which exactly correspond to recursive Markov chains. We show that every pPDA can be transformed into a stateless pPDA (called "pBPA") whose runtime and further properties are closely related to those of the original pPDA. This result substantially simplifies the analysis of runtime and other pPDA properties. We prove that for every pPDA the probability of performing a long run decreases exponentially in the length of the run, if and only if the expected runtime in the pPDA is finite. If the expectation is infinite, then the probability decreases "polynomially". We show that these bounds are asymptotically tight. Our tail bounds on the runtime are generic, i.e., applicable to any probabilistic program with unbounded recursion.
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