First of all boys & girls It is not "computers against each other".... It is the percentage of total volume executed during a time period. Usually it is calculated on a daily basis. As for the rest of your comments
This whole "program trading" issue is hogwash. Fundamentally, it's still people trading. Afterall, someone had to come up with the algorithm, implement the algorithm, and manage the algorithm. All the computers do is speed things up dramatically.