1. A computer-implemented method to implement a vector collective operation on a parallel computer comprising a plurality of compute nodes operatively connected via a first network having a network processing element, each compute node having at least a processor and a memory, the method comprising: performing a collective operation using the network processing element, in order to determine a plurality of displacements for the vector collective operation; generating descriptors for the vector collective operation based on the plurality of displacements, wherein the descriptors for the vector collective operation comprise a descriptor for each of the plurality of compute nodes, and wherein each descriptor comprises a base address of data and a message length of the data for the respective compute node for performing the vector collective operation; and performing the vector collective operation by the plurality of compute nodes and using the generated descriptors.