Neural processing devices for handling real-valued inputs

A device for use in a neural processing network, comprising a memory having address lines and a plurality of storage locations at each of which a number representing a probability is stored;

• a real-number to digital converter which receives a plurality of real-valued numbers each in the range of 0 to 1 and produces at its output a corresponding plurality of synchronized parallel pulse trains which are applied to respective address lines of the memory as a succession of storage location addresses, thereby to selectively address each storage location of said plurality of storage locations as an addressed storage location the probability of a pulse representing a 1 being present in an address on a given address line being equal to the value of the real-valued number from which was derived an applied one of the pulse trains to that address line;
• a comparator for successively receiving as an input the numbers stored at each of the addressed storage locations;
• a noise generator for inputting to the comparator a succession of random numbers, representing noise;
• means for causing to appear at an output of the comparator a succession of output signals each having a first or second value depending on the values of the numbers received from the addressed storage locations and the noise generator, the probability of the output signal having a given one of the first and second values being determined by the number at one of the addressed storage locations;
• an integrator for integrating the output signals from the comparator;
• means for receiving signals from an environment, the signals representing a successful action or an unsuccessful action by the network;
• means for changing the value of the numbers stored at the addressed storage locations if a success signal is received, in such a way as to increase the probability of the successful action;
• means for changing the value of the number stored at the addressed storage locations if a failure signal is received, in such a way as to decrease the probability of the unsuccessful action;
• an address counter for counting the number of times each of the storage locations is addressed;
• and means for increasing or decreasing the values of the numbers stored at the addressed storage locations in dependence on the number of times each of the storage locations is addressed, as counted by the address counter;
• and two further counters for each of the storage locations, one of said further counters having contents subject to an increment on each occasion when the storage location is addressed and the output signal of the device has the first value, and the other of said further counters having contents subject to an increment on each occasion when the storage location is addressed and the output signal of the device has the second value, the contents of both said further counters being subject to a decay factor each time any storage location is accessed, the values of the numbers stored at the addressed storage locations being increased or decreased in dependence on the contents of said further counters.