A reconfigurable tree apparatus with a bypass mode and a method of using the reconfigurable tree apparatus are disclosed. The reconfigurable tree apparatus uses a short-circuit register to selectively designate participating agents for such operations as barriers, multicast, and reductions. The reconfigurable tree apparatus enables an agent to initiate a barrier, multicast, or reduction operation, leaving software to determine the participating agents for each operation. Although the reconfigurable tree apparatus is implemented using a small number of wires, multiple in-flight barrier, multicast, and reduction operations can take place. The method and apparatus have low complexity, easy reconfigurability, and provide the energy savings necessary for future exa-scale machines.