1. A method of embedding a collective network in a parallel computer system organized as a torus network, said computer system including a multitude of modes, each of the nodes having a plurality of receivers and a plurality of senders, the method comprising: adding to the torus network a central collective logic to route messages among at least a group of said nodes in a tree structure, wherein, at defined times, one of said group of nodes is a root node and the others of said group of nodes are leaf or intermediate nodes, and including routing messages from the leaf or intermediate nodes to the root node in an up tree direction; processing the messages being routed from the leaf or intermediate nodes to the root node to form a processed message; and sending the processed message back from the root node to at least one of the leaf, intermediate or root nodes.