PURPOSE: To improve the reliability of the solution of such a complicated problem that shows the conspicuous multi-peak properties by changing the range of perturbation of a state variable in accordance with the value of a temperature parameter.

CONSTITUTION: A CPU 10 initializes the state variable X, the initial temperature T0 and the time step (respective function) K against the subject function (energy function) E (X) that is minimized. Then the CPU 10 calculates (evaluates) the value of the function E(X). If the present temperature parameter TK is larger than the prescribed value, the CPU 10 decides the intermediate processing between the initial state and the middle state of a minimization problem and sets a large range of perturbation for the variable X. Under such conditions, TK=T0/(log(2+K)) is satisfied. If the parameter TK is smaller than the prescribed value, the CPU 10 decides the intermediate processing between the middle state and the final state of the minimization problem. Thus the range of perturbation is reduced for the variable X.