code: def tic(self):
          
          if self.step % self.interval == 0:
              for exe in self.exes:
                  for array in exe.arg_arrays:
                      array.wait_to_read()
                  for array in exe.aux_arrays:
                      array.wait_to_read()
              self.queue = []
              self.activated = True
          self.step += 1
docs: Start collecting stats for current batch.
          Call before calling forward.