1. A method for determining an optimum policy by using a Markov decision process in which T subspaces each have at least one state, comprising: identifying, with a processor, T subspaces that are part of a fixed state space, T being a natural number, the identified T subspaces being in sequence, the Markov decision process being cyclic by having the (T+1)-th subspace of the T subspaces equal to the first subspace of the T subspaces; selecting the t-th subspace among the identified T subspaces, t being a natural number that is less than or equal to T; computing a probability of, and an expected value of a cost of, reaching from one or more states in the selected t-th subspace to one or more states in the t-th subspace in a next cycle; and recursively computing a value and an expected value of a cost based on the computed probability and expected value of the cost, in a sequential and decrementing manner starting from the (t−1)-th subspace to the (t−2)-th subspace and so forth down to the (t+1)-th subspace, via the first subspace and the T-th subspace, wherein selection of a subspace having fewest states among the T subspaces is received as the t-th subspace.