1. A method of executing a gather operation on a parallel computer that includes a plurality of compute nodes, the method comprising: dividing, by each task in an operational group of tasks of a compute node, a send buffer containing contribution data into a plurality of chunks of data, each chunk of data located at an offset within the send buffer; sending, by each task in the operational group of tasks, one chunk of data to a root task through a data communications thread for each chunk of data including instantiating a separate data communication thread for each chunk of data, wherein each chunk of data is sent in parallel from the compute node to the root task; receiving the chunks of data by the root task; and storing, by the root task, each chunk of data in a receive buffer of the root task in dependence upon the offset of each chunk of data within the send buffer.