The advantages to employ the geometrical average are as follows.
 (1) Changes of the reference times only shift "fMark" by a constant value. 
 (2) It can avoid being too strongly affected by the results of a few programs.
     On the other hand, if the performance index is defined as
     an arithmetic average of (ref time)/(CPU time),
     and if a program can be quickly executed compared with the other programs,
     the index is determined only by the program.
     If the performance index is defined as the reciprocal of an arithmetic 
     average of (CPU time)/(ref time), the index is too strongly affected
     by a few programs whose CPU time is long compared with those of the
     other programs.