
Posted by: stak
Posted on: 20061030 22:12:13
an idea i had a while back but forgot about until earlier today was trying to use physical processes to solve math/software problems. the specific idea i had was to use electricity's property of always finding "the path of least resistance" to solve a graphsearch problem.
if you can represent a search graph using a bunch of resistors, then theoretically, you could plug in your resistor network and let the electric current find the solution for you. since it checks all paths in parallel, it would work in pretty much constant time. the problem with it is that it would only be faster than a software search algorithm for a large enough graph, and for graphs of that size building the resistor network becomes nontrivial. if it were possible to turn this into a more general massively parallel computer of some sort, it might be worth it, but it seems unlikely.
another related thing that came up was using physical processes to generate oneway functions in math. so, for example, if you were given the description of a container and a ball within the container, along with the initial position and velocity of the ball, you could use the laws of physics to figure out where the ball ends up. however, given the description of the container and the final position of the ball, it's practically impossible (i think) to figure out the initial position and velocity of the ball. in this case, it turns out to be very similar to a hash function, since the input space of the function (ball position and velocity) is much larger than the output space (ball position), and multiple inputs can map to the same output. so in fact it's actually impossible to reverse the function.
there's probably some other physical process out there that's a better candidate..


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linear time? the current travels at a finite speed and should take longer to go through longer wires.