1. A method for reducing an energy consumption in a parallel computing system that includes plural resources, the method comprising: receiving a computing job to be performed by the parallel computing system; determining a number of resources of the plural resources to be used for performing the computing job by selecting, as the number of resources, a number that minimizes the energy consumption when executing the computing job during a required time by searching a preset table stored in the parallel computing system, wherein the preset table is populated prior to determining the number of resources based on running various computing jobs on sets of the plural resources; and distributing the computing job to the determined number of resources.