1. A method of optimizing use of a configuration memory of a reconfigurable processor, the method comprising: analyzing parallelism of a loop of a program code based on an architecture of the reconfigurable processor and details of the configuration memory; scheduling groups of function units (FUs), which will be activated in each cycle of the loop, according to the analyzed parallelism to generate configuration data of each cycle; and sequentially mapping classification letters for classifying the generated configuration data and the groups with respect to the scheduled groups in adjacent cycles in at least one row of the configuration memory.