1. A method of performing a global barrier operation in a parallel computer, the parallel computer comprising a plurality of compute nodes, the compute nodes coupled for data communications, each compute node executing a plurality of tasks, with one task on each compute node designated as a master task, the method comprising: for each task on each compute node until all master tasks have joined a global barrier: determining whether the task is a master task; if the task is not a master task, joining a single local barrier; if the task is a master task, joining the global barrier and the single local barrier only after all other tasks on the compute node have joined the single local barrier.