8 ms·
Von Neumann-Landauer limit
- agumonkey 9y agoAs inspiring as thought provoking.
- _nalply 9y agoYes. I imagine the last probe doing its last bit flip in the heat death of the universe. Then nothing can be computed anymore and all what will happen is the decay of the matter of the probe. So sad.
- guskel 9y agoI believe there is some breakthrough yet to be found in the intersection of entropic gravity and computational limits.
- Synaesthesia 9y agoI’d be curious to hear more about that idea but thank you for introducing me to this theory of entropic gravity.
- malux85 9y agoMe too - any links or articles for the best material much appreciated
- Synaesthesia 9y agoHaving read some more about this entropic gravity theory it does have quite a few pretty strong criticisms, detailed on the the wiki page.
- philipkglass 9y agoThe usual extropian retort to this limit has been "reversible computing," but as far as I can tell there has been little work on reversible computing hardware -- far less than quantum computing. It looks like the University of Florida made some hardware in the early 2000s. Can anyone offer insights about why hardware research is so scarce here? Are there reasons to think it's a dead end prior to fabricating anything? https://en.wikipedia.org/wiki/Reversible_computing https://en.wikipedia.org/wiki/Reversible_computing EDIT: searching Google Scholar, it looks like only ~50 papers/books mention reversible computing in the past year, compared to 1000+ for quantum computing.
- bo1024 9y agoJust my guess, but the practical motivation is probably not there -- we are so far from the levels of efficiency at which the Landauer principle is noticeable.
- Strilanc 9y agoReversible computing still requires energy (or rather neg-entropy). It's used to perform error correction. Otherwise the computer won't last very long.
- kobeya 9y agoIt’s also used to offload bits. Real computers don’t have infinite tape.
- tgb 9y agoReversible computation is inherently slow computation and the main advantage is it lets you get below this limit but current computers are still many (dozens?) of orders of magnitude off from reaching that limit. Until then, you'd be better off just improving efficiency of non-reversible computers.
- abecedarius 9y agoThat wiki page says "Although the Landauer limit was millions of times below the energy consumption of computers in the 2000s and thousands of times less in the 2010s,[3] proponents of reversible computing argue that this can be attributed largely to architectural overheads which effectively magnify the impact of Landauer's limit in practical circuit designs, so that it may prove difficult for practical technology to progress very far beyond current levels of energy efficiency if reversible computing principles are not used.[4]" On a skim it looks like [4]'s argument is that people have been criticizing the overhead of fully reversible circuits, but only 'conditionally reversible' circuits are needed for the power benefits.
- shpx 9y agoRelated discussion https://news.ycombinator.com/item?id=14002160 https://news.ycombinator.com/item?id=14002160 https://news.ycombinator.com/item?id=14146677 https://news.ycombinator.com/item?id=14146677
- md224 9y agoI picked up The Information by James Gleick when I was visiting the Living Computers Museum + Labs in Seattle[1]. Really interesting book... talks about the development of language, the birth of computing, the concept of randomness, the physics of information, etc. A fascinating and comprehensive overview of the topic. [1] This place is awesome and you should check it out if you're in the area: http://www.livingcomputers.org http://www.livingcomputers.org
- emmelaich 9y agoI remember reading Feynman's thought experiment and him deciding that it doesn't require any energy to flip a bit.[1] How does that square with Landauer's limit? [1] Apologies for the lack of reference. I'll try and find it.
- kobeya 9y agoI’m not sure how it squares with physics. I’d recommend finding that reference.
- emmelaich 9y agoWell, perhaps it's only a theoretical minimum. It agrees with kT ln 2 when T=0 right?
- kobeya 9y agoT is never 0.
- emmelaich 9y agoYeah I know :-) But OK here's a reference of sorts. Not by Feynman but by Bennet and Landauer. https://www.scientificamerican.com/article/the-fundamental-physical-limits-of-computation/ https://www.scientificamerican.com/article/the-fundamental-p... "there is no minimum amount of energy that must be expended in order to run a Brownian clockwork Turing machine." Also interesting but I didn't find the exact thing I was looking for: Simulating Physics with Computers Richard P. Feynman https://people.eecs.berkeley.edu/~christos/classics/Feynman.pdf https://people.eecs.berkeley.edu/~christos/classics/Feynman.... Richard Feynman and Computation https://cds.cern.ch/record/411350/files/p101.pdf https://cds.cern.ch/record/411350/files/p101.pdf
- kobeya 9y agoWell for example, T cannot be less than the temperature of the cosmic microwave background. You can make regions with lower T, but only by pumping heat out in some way, which is more energy to do. Being on mobile and not able to explore in depth, that quote sounds like a variant of Maxwell’s demon. It is correct to say that the Landauer limit is not due to a single physical law that must hold true, but rather a lack of knowledge about the state of the universe and the fact that acquiring that knowledge to do a “free” bitflip requires at least equivalent energy expenditure as that bitflip. TANSTAAFL.
- deepnotderp 9y agoAs interesting as it is to think about the limit, it's so pointless from a practical point of view since the cost of computation is dwarfed by the cost of data movement in modern machines.
- davidivadavid 9y agoRecently mentioned in Venkat Rao's Breaking Smart newsletter.
- bandrami 9y agoSo you're telling me ignorance can combat global warming?