4 ms·
Slightly off topic, but it's widely accepted among physicists that the act of computation expends energy [1]. Thus, there are actually limits to how much the c
by csense 14y ago
Slightly off topic, but it's widely accepted among physicists that the act of computation expends energy [1]. Thus, there are actually limits to how much the cost of a given computation can be reduced, regardless of how cleverly we build the computer, or what we build it out of (silicon, DNA, fiber optics, whatever) [2].
[1] http://en.wikipedia.org/wiki/Landauer%27s_principle http://en.wikipedia.org/wiki/Landauer%27s_principle
[2] If we're willing to use algorithms that don't destroy information, or willing to operate at arbitrarily low temperatures, as I understand it there's no theoretical limit to how small we can make the energy costs, but these restrictions seem highly impractical.
- deleted 14y ago[deleted]
- i_cannot_hack 14y agoYour wikipedia link is broken. Try this: http://en.wikipedia.org/wiki/Landauer%27s_principle http://en.wikipedia.org/wiki/Landauer%27s_principle
- csense 14y agoThanks, edited and fixed!
- kragen 14y agoWhile this is true, current hardware is several orders of magnitude away from the Landauer limit, so there's still quite a bit of room for building computers more cleverly before we confront it. However, reversible algorithms are not in fact particularly impractical. They require a somewhat different way of thinking about things, but they're dramatically easier than e.g. quantum computing speedup. Similarly, cryogenic computation is entirely reasonable, especially in space.
- ars 14y ago"several orders of magnitude"??? We are an order of magnitude worth of orders of magnitude away from that limit. Specifically: 5.539×10^11 times as much energy (for the I7 920, picked randomly). http://www.wolframalpha.com/input/?i=130+w+%2F+%280.0178+electron+volt+*+82300+MIPS+%2F+instruction%29 http://www.wolframalpha.com/input/?i=130+w+%2F+%280.0178+ele...
- kragen 14y agoThanks for doing the calculation! I'm not checking it right now, but it's in the right range. However, in the tradeoff between shortest time of execution of serial programs and power efficiency per instruction, the i7 is way over at the shortest-time-of-execution extreme. Common GPUs are about a thousand times as power-efficient, and many embedded microcontrollers are nearly as power-efficient as GPUs. Check out the Bitcoin hardware performance Wiki pages for hard data.