> No, you don't run into the same constraints. The reason is that in
> the case of the VR, the bits which must be reversed are all bits in
> your computer. You had complete control over the design of this system
> and you can arrange for the system to be reversible.
> In the case of a robot interacting with the real world of grass and trees
> and rocks, those systems are not reversible. They contain dynamics which
> increase entropy and prevent reversibility.
> You can reverse simulated grass, simulated trees, simulated rocks,
> and their interactions with a simulated robot in a virtual reality.
> This is a special case of creating a reversible computer. But you cannot
> reverse real world systems. That is the fundamental difference.
Ah. Now I see what you're getting at. Yes, energy costs of computations that
are completely internal to a computer can be lower than those of
computations that are intimately tied to the external world.
However, you still don't gain anything by using a VR. For example, the
efficient implementation of your example is to dispense with the robot and
its VR maze entirely, and simply run the robot's search algorithm on a
mathematical model of the topology of the maze. All the other features of
the VR are wasted bits. The same is true of any computation - running a
full-blown VR is far more expensive than running an abstract operation that
only implements the features you are interested in working with.
Which returns me to my original comment that VRs are a social amenity for
humanlike sentients, not a tool for making computers run faster (or cooler,
which amounts to the same thing).
This archive was generated by hypermail 2b29 : Thu Jul 27 2000 - 14:10:38 MDT