A node state storage unit stores therein information about a free state of each of the computation nodes. A search data storage unit has a data structure in which a state where the X-axis is crossed is developed into a virtual X-axis provided on the right end of the X-axis. By referring to the node state storage unit, a searching unit searches for the number of successive free nodes in the increasing directions of the X-axis including the virtual X-axis and the Y-axis, while using the computation node at each of the X-Y coordinate positions as a starting point, and writes a search result into the search data storage unit.