1. An engine control apparatus that calculates a control target value of one actuator or control target values of a plurality of actuators, comprising: a multicore processor in which a plurality of cores are arranged in a latticed manner, wherein a plurality of lattice points that are arranged on a two-dimensional orthogonal coordinate system having axes representing a first operating condition and a second operating condition respectively are associated with at least one or some of the plurality of the cores respectively on one-on-one level on a same line as on the two-dimensional orthogonal coordinate system, and a calculation program for calculating an optimal control value of the one actuator at the associated lattice points or calculation programs for calculating optimal control values of the plurality of the actuators at the associated lattice points are allocated to at least one or some of the plurality of the cores respectively, each of the cores with which the lattice points are associated respectively is programmed, in a case where an operation area on the two-dimensional orthogonal coordinate system to which a current operating point belongs is an area that is defined by the lattice point associated with each of the cores itself, to transmit to an interpolation calculation core an optimal control value at the relevant lattice point that is calculated by each of the cores itself, the interpolation calculation core is programmed to perform an interpolation calculation of an optimal control value at the operating point using optimal control values at all the lattice points that define the operation area, and the multicore processor outputs the optimal control value at the operating point, which is obtained through the interpolation calculation, as the control target value.