1. An apparatus for determining a system configuration for performing a collective operation on a parallel computer, the parallel computer comprising a plurality of compute nodes, the compute nodes coupled for data communications over a data communications network, the apparatus comprising a computer processor and a computer memory operatively coupled to the computer processor, the computer memory including computer program instructions that, when executed by the computer processor, cause the apparatus to carry out the steps of: selecting from a plurality of system configurations, by a performance measurement module, a system configuration on the parallel computer for executing the collective operation; executing, by the performance measurement module, the collective operation on the selected system configuration on the parallel computer; determining, by the performance measurement module, performance metrics associated with executing the collective operation on the selected system configuration on the parallel computer; selecting, by the performance measurement module using a simulated annealing algorithm, a plurality of test system configurations on the parallel computer for executing the collective operation, wherein the simulated annealing algorithm specifies a similarity threshold between the plurality of test system configurations and the selected system configuration; executing, by the performance measurement module, the collective operation on each of the test system configurations; and determining, by the performance measurement module, performance metrics associated with executing the collective operation on each of the test system configurations.