1. An information processing system, comprising: a plurality of information processing apparatuses connected with a network, wherein one of the plurality of information processing apparatuses comprises: a first allocation unit to identify, for each subnetwork of a plurality of subnetworks included in the network, one information processing apparatus from among information processing apparatuses included in the subnetwork, and assign to the identified one information processing apparatus, a first Reduce processing that is a processing to summarize results of a Map processing executed for data held in the information processing apparatuses included in the subnetwork; and a second allocation unit to allocate to any one of the plurality of information processing apparatuses, a second Reduce processing that is a processing to summarize results of the first Reduce processing executed for each subnetwork of the plurality of subnetworks.