Controller and control method for internal combustion engine

A controller for an internal combustion engine mounted on a vehicle, the controller being configured to control the internal combustion engine by operating an operated unit of the internal combustion engine, the controller comprising:

• a memory device, which is configured to store, in advance
• a relationship defining data set that defines a relationship between a state variable that represents a state of the vehicle, which includes a state of the internal combustion engine, and an operated amount of the operated unit, the relationship defining data set being updated during traveling of the vehicle, and
• an adapted data set that is used to calculate the operated amount based on the state variable, the adapted data set not being updated during traveling of the vehicle;
• and
• an execution device, which is configured to execute an operation of the operated unit, wherein
• the execution device is configured to execute:
• a first operation process that operates the operated unit by the operated amount, which is calculated on a basis of the state variable, using the adapted data set;
• a second operation process that operates the operated unit by the operated amount that is defined by the relationship defining data set and the state variable;
• a reinforcement learning process that calculates a reward on a basis of the state variable when the operated unit is being operated using the second operation process, and updates the relationship defining data set so as to increase an expected return of the reward on a basis of the state variable, the operated amount, and the reward;
• a switching process that switches a process that operates the operated unit in accordance with the state of the vehicle between the first operation process and the second operation process;
• and
• a recording process that obtains a value of the state variable used in the calculation of the operated amount using the first operation process during the operation of the operated unit using the second operation process, and records time-series data of the obtained value of the state variable to the memory device.