A computation system for computing interactions in a multiple-body simulation includes an array of processing modules arranged into one or more serially interconnected processing groups of the processing modules. Each of the processing modules includes storage for data elements and includes circuitry for performing pairwise computations between data elements each associated with a spatial location. Each of the pairwise computations makes use of a data element from the storage of the processing module and a data element passing through the serially interconnected processing modules. Each of the processing modules includes circuitry for selecting the pairs of data elements according to separations between spatial locations associated with the data elements.