Electronic control device and neural network update system

A neural network update system that includes a server and an electronic control device and updates a neural network including a plurality of neurons and a connection information group including a plurality of pieces of connection information that associate the neurons with each other, wherein

• the server includes a storing part and an arithmetic part,
• the storing part stores a first connection information group for deciding an output value when an input value is given,
• the arithmetic part includes
• a coefficient identifying section that identifies a second connection information group that is a plurality of pieces of the connection information having a degree of influence on predetermined data, the degree of influence exceeding a predetermined value, when the predetermined data is given as the input value, and
• a pruning section that deletes at least one piece of connection information from the first connection information group to create the third connection information group on a basis of the first connection information group and the second connection information group, and
• the electronic control device stores a neural network including the third connection information group.