P-complete

Discounted Markov Decision Process (DMDP)

Category: Algebra

Input

A stationary Markov decision process $M = (S, c, p)$ and a real number $\beta \in (0, 1)$.

Problem

Is the minimum expected cost of $$\sum_{t=0}^{\infty} c(s_t, \delta(s_t, t)) \beta^t$$ over all policies $\delta$ equal to $0$?

Definitions

See FHMDP. This problem is infinite horizon, that is, there is no time bound.

Status

$\P$-complete (Papadimitriou and Tsitsiklis [1]).

Remarks

The problem can be phrased as a linear programming problem and solved in polynomial time. The same construction as used in FHMDP can be used to show this problem is $\P$-complete.

The Infinite Horizon, Discounted, Deterministic Problem is in $\NC$ [1]. The deterministic problem requires that $p$ only has values $0$ or $1$.

References

  1. C. H. Papadimitriou and J. N. Tsitsiklis (1987). The complexity of Markov decision processes.
  2. Greenlaw, R., Hoover, H. J., and Ruzzo, W. L. (1995). Limits to Parallel Computation: P-Completeness Theory. Oxford University Press. Problem A.8.2.