1. A computer readable medium having a computer readable program code, said computer readable program code to execute a method for calculating a tuning parameter for a numerical computation library, the computer readable program code being arranged to calculate an optimum tuning parameter, based on a preset objective function, for use in executing the numerical computation library, said method comprising the steps of: reading the numerical computation library; reading the objective function; selecting the tuning parameter; setting a user policy as plural policy parameters regarding speed performance and computational accuracy of the numerical computation library; reading, from preset execution histories of numerical computation libraries, execution histories of the numerical computation library; determining exploited points, each exploited point is defined by a pair of speed performance and computational accuracy of a record based on the execution histories having been read in; calculating the optimum tuning parameter for the numerical computation library by using the objective function that optimizes the speed performance and computational accuracy constituting two mutually opposing elements; and outputting a calculation result of the objective function, wherein the step of setting a user policy as plural policy parameters includes setting a first target policy parameter specifying an ideal value of the speed performance, a first mandatory policy parameter specifying a minimum required value of the speed performance, a second target policy parameter specifying an ideal value of the computational accuracy, and a second mandatory policy parameter specifying a minimum required value of the computational accuracy, and wherein, in the step of calculating the optimum tuning parameter, minimizing the objective function selects, from the execution histories, a determined exploited point within a domain defined by the plural policy parameters and a value of the tuning parameter of the selected exploited point is the calculated optimum tuning parameter.