A data processing device configured to: repeat, at a time of searching for a solution, a search process that includes determining whether to permit a change in a value of a first state variable among a plurality of state variables based on a first local field, updating a value of the first state variable, the first local field, a second local field, and a total value when the change in the value of the first state variable is permitted, determining whether to permit a change in a value of a first auxiliary variable among a plurality of auxiliary variables based on the second local field, and updating the value of the first auxiliary variable and the first local field when the change in the value of the first auxiliary variable is permitted, and adjust the value of the coefficient based on the total value or whether there is the violation.