* @return a string representation of the percent occupancy of state, or NA is not possible
*/
@Requires({"engine != null", "state != null"})
@Ensures("result != null")
private String getThreadEfficiencyPercent(final GenomeAnalysisEngine engine, final ThreadEfficiencyMonitor.State state) {
final ThreadEfficiencyMonitor tem = engine.getThreadEfficiencyMonitor();
return tem == null ? "NA" : String.format("%.2f", tem.getStatePercent(state));
}