/**
  * Performs workload dependent preconditioning - this method must be 
  * implemented by sub-classes. It should return one of the following 
  * values:
  *   TRUE:  preconditioning successful and steady state achieved
  *   FALSE: preconditioning successful but steady state not achieved
  *   NULL:  preconditioning failed
  * @return boolean
  */
 public function wdpc()
 {
     $status = NULL;
     $verbose = isset($this->options['verbose']) && $this->options['verbose'];
     BlockStorageTest::printMsg(sprintf('Initiating workload dependent preconditioning and steady state for XSR test'), $verbose, __FILE__, __LINE__);
     // TODO
     return $status;
 }