1. An apparatus comprising: a crossbar array of signal lines and control lines; an input controller in circuit with the control lines, the input controller to select one of the control lines; first resistive elements connected between corresponding ones of the control lines and corresponding ones of the signal lines, the first resistive elements having first conductances set to operate as a matrix of probabilities that define a fixed transition kernel of a Markov Chain; and second resistive elements in circuit with the signal lines, the second resistive elements having second conductances set to select one of the signal lines exclusive of others of the signal lines based on a subset of the probabilities in the matrix of the probabilities, the subset of the probabilities defined by a subset of the first conductances of ones of the first resistive elements corresponding to the selected control line.