1. A method of locating hardware faults in a data communications network of a parallel computer, the parallel computer comprising a plurality of compute nodes and a data communications network that couples the compute nodes for data communications and organizes the compute node as a tree, the method comprising repeatedly carrying out the following steps for a plurality of branch compute nodes of the parallel computer: identifying a next compute node as a parent node and a root of a parent test tree; identifying for each child compute node of the parent node a child test tree having the child compute node as root; running a same test suite on the parent test tree and each child test tree; and identifying the parent compute node as having a defective link connected from the parent compute node to a child compute node if the test suite fails on the parent test tree and succeeds on all the child test trees.