A
parallel processing device that computes a
hierarchical neural network, the
parallel processing device includes: a plurality of units that are identified by characteristic unit numbers that are predetermined identification numbers, respectively; a
distribution control section that, in response to input as an input value of an output value outputted from one of the plurality of units through a unit output
bus, outputs
control data including the input value inputted and a selection unit number that is an identification number to select one unit among the plurality of units to the plurality of units through the unit input
bus; and a common storage section that stores in advance
coupling weights in a plurality of
layers of the
hierarchical neural network, the
coupling weights being shared by plural ones of the plurality of units. Each of the units includes: a
data input section that receives
control data as an input from the
distribution control section through the unit input
bus; a unit number match judgment section that judges as to whether a selection unit number included in the
control data inputted in the
data input section matches the characteristic unit number; a unit
processing section that, based on an input value included in the control data inputted in the
data input section, computes by a computing method predetermined for each of the units; and a data output section that, when the unit number match judgment section provides a judgment result indicating matching, outputs a computation result computed by the unit
processing section as the output value to the
distribution control section through the unit output bus, wherein, based on the
coupling weights stored in the common weight storage section, the unit
processing section executes computation in a forward direction that is a direction from an input layer to an output layer in the
hierarchical neural network, and executes computation in a backward direction that is a direction from the output layer to the input layer, thereby updating the coupling weights.