1. An apparatus comprising: a first configurable circuit comprising: a processing circuit comprising at least one stochastic circuit arranged to implement a technique for solving stochastic problems; and at least one control circuit to configure the processing circuit to solve a particular stochastic problem by controlling a provision of information to the processing circuit, the information comprising a probability distribution from which samples are to be produced to solve the particular stochastic problem, wherein the at least one control circuit is adapted to provide a predetermined number of values to the processing circuit and, when a number of other stochastic problems upon which the particular stochastic problem conditions depends is less than the predetermined number, the at least one control circuit performs a masking operation to indicate to the processing circuit that fewer than the predetermined number of values are being provided.