If you do not specify an experiment name, the default experiment name is used. The Collector uses the MPI rank to construct an experiment name with the standard form experiment.m.er, where m is the MPI rank. The stem, experiment, is the stem of the experiment group name if you specify an experiment group, otherwise it is test. The experiment names are unique, regardless of whether you use a common file system or a local file system. Thus, if you use a local file system to record the experiments and copy them to a common file system, you do not have to rename the experiments when you copy them and reconstruct any experiment group file. In most cases, you should allow the Collector to create the experiment names to ensure unique names across all file systems.