[HN Gopher] MemComputing vs. Quantum Computing
___________________________________________________________________
MemComputing vs. Quantum Computing
Author : velmu
Score : 15 points
Date : 2023-05-11 20:03 UTC (2 hours ago)
(HTM) web link (www.memcpu.com)
(TXT) w3m dump (www.memcpu.com)
| generalizations wrote:
| I didn't know that memcomputing had already been solved. That's
| fantastic news...here's hoping it doesn't remain ridiculously
| expensive.
|
| I take issue with this line, however.
|
| > Both MemComputing and quantum computers are physics-based
| approaches to computation. That is, they set aside many of the
| foundations of traditional computer science and rethink
| computation from the ground up. For example, they don't follow
| the von Neumann architecture, the computing framework that
| separates the processing unit from the memory unit, which is
| employed by all of today's computers.
|
| From what I recall of Von Neumann, his titular architecture was
| the 'first draft' of what he was going for, and we've been stuck
| with it before he could figure out version two. He based his
| design on the notion of cellular automaton, where of course the
| processing units are not separated from the memory units.
|
| Rather, from what I recall, the Architecture we've been stuck
| with was just his best attempt at emulating what's here called
| memcomputing, but with the limited engineering resources at his
| disposal. If he hadn't died, I think he would have been trying to
| do proper memcomputing in the second draft. Only took us the
| better part of a century to catch up!
| bdamm wrote:
| I view the von Neumann architecture as more of a reference.
| When you get down to it, there's so much hardware trickery at
| play that it isn't easy to cleanly say that any specific
| computer fits precisely into what Von Neumann was describing.
| Consider multi-layer caches, CPUs that execute directly out of
| RAM, mapped IO, or even micro machine code design where the
| instruction set of the CPU is really an emulated layer on top
| of a deeper processor, and it's really hard to reconcile these
| modern machines as a Von Neumann architecture. I'd say that
| computer design has taken all the pragmatic approaches
| available. We have had wholesale architecture reboots every ten
| years or so. Even modern x86 doesn't resemble the original all
| that much.
|
| However, as a conceptual bundle to teach aspiring computer
| science students about hardware? It's great!
|
| Requiring that our software be able to simulate a Turing
| machine has probably held us back more, although that basic
| abstraction did get us to this point so in no way am I
| besmirching the work of Dr. Turing.
| kwooding wrote:
| Ever since my PhD work (where I worked with some pretty
| obscure computing architectures), the phrase "Von Neumann
| Architecture" makes think immediately of D H Lehmer's quote
| [1] on working with ENIAC:
|
| > Can we use the high speed computer to do the sieve process?
| This was a highly parallel machine, before von Neumann
| spoiled it.
|
| [1]: https://history.computer.org/pioneers/lehmer.html
| inasio wrote:
| Their tagline at the end:
|
| ```MemComputing is available today and is delivering the
| performance expected of quantum computers across a wide range of
| valuable optimization problems in industry. ```
|
| Quantum computers unfortunately are not expected to do well
| against traditional OR algorithms in most (all?) OR problems
| (Grover search only helps in brute force search; Shor it not
| quite an OR application, and relies on quantum effects), so not
| really a strong selling point in my view
| thxg wrote:
| MemComputing mainly present themselves as optimizers: Their
| machine can solve real optimization problems, in practice, today.
| This is very good because, through that lens, we can skip the BS
| and go straight to the facts. The evaluation criteria for any
| optimization approach/algorithm are:
|
| - the quality of the solutions found (in the best case: optimal
| solutions)
|
| - the presence or absence of optimality guarantees (for example,
| some algorithms provide optimal solutions very often, but cannot
| guarantee it 100%)
|
| - the time (or computational cost) needed to find such solutions
|
| Furthermore, the state-of-the-art (SOTA) is well known for most
| types of optimization problems. In this article, they present a
| list of real and practical applications, so let us have a look at
| them one by one:
|
| 1.1 Traffic flow optimization
|
| Simple flow problems can be solved in polynomial time (and
| quickly in practice), so there is no need for anything fancy.
| Once you introduce additional constraints or discrete variable,
| the SOTA is mixed-integer programming for offline problems. For
| online problems it's more complicated. In both cases, I am not
| aware of any application in which MemComputing can reach SOTA.
|
| 1.2 Vehicle routing & scheduling
|
| Here, depending on your computing time constraints, needs for
| solution quality and/or optimality guarantees, the SOTA can be
| constraint programming (gecode, OptaPlanner), local search
| heuristics (LocalSolver), or mixed-integer programming
| (CPLEX/XPress/Gurobi) with column generation. MemComputing is
| nowhere to be seen again.
|
| 1.3 Supply chain optimization
|
| This is a very broad field, but in general mixed-integer
| programming is king here.
|
| 2.1 Protein folding
|
| Here there is quite an objective measure: the biennal CASP
| competition. This is where AlphaFold made a splash in 2022.
| MemComputing has never participated.
|
| 2.2 Genome sequencing
|
| I am not knowledgeable enough to comment here.
|
| 2.3 Radiotherapy treatment
|
| I am not very knowledgeable here either, but last I looked mixed-
| integer programming approaches were favored.
|
| 3.1 Portfolio risk optimization
|
| Various types of branch-and-bound solvers. Mixed-integer
| linear/quadratic/convex programming. No MemComputing.
|
| 3.2 Detecting market instabilities
|
| No idea.
|
| 3.3 Optimizing trading trajectories
|
| No idea.
|
| 4.1 Training neural networks
|
| Many people here know how this is done. Stochastic gradient
| descent on GPUs or TPUs. No MemComputing involved. How can they
| even claim to be active in this field?
|
| 4.2 Detecting statistical anomalies
|
| Vague.
|
| 4.3 Classifying unstructured datasets
|
| No idea.
|
| The problem is that if you invent a new optimization algorithm,
| it is very easy to find one instance of one problem for which
| your algorithm works well. They did literally that in a paper
| [1]: They took a library of mixed-integer programming problem
| instances containing 270 benchmark problems, and published a
| whitepaper showing that they beat a SOTA solver on one of them. A
| single instance out of 270!
|
| The really hard part is the opposite: given a class of problems,
| find an algorithm that beats the SOTA. MemComputing has never
| done that. Combined with their propensity for grand claims backed
| by misleading evidence, MemComputing have accumulated a lot of
| badwill from the academic community over the years. My suspicion
| is that, while on the surface this post seems to put their
| approach in contrast to quantum computing, what they really try
| to do here is ride on the quantum computing hype wave.
|
| [1] https://arxiv.org/abs/2003.10644
| marcodiego wrote:
| > Somewhat surprisingly, just the emulation of this circuit in
| software (Virtual Memcomputing Machine) provides solutions to
| these problems orders of magnitude faster and more accurately
| than today's state of the art technologies.
|
| Looks like market speech to me.
| ljlolel wrote:
| Yea that can't be true. Otherwise you would be able to
| systematically modify an existing algorithm to a new one to
| mirror the Memcomputing method and create new state of the art
| algorithms that are faster by orders of magnitude? And somehow
| that hasn't already been discovered and published and used
| preferentially to the published state of the art? Nonsense.
| IIAOPSW wrote:
| Oranges vs Apples.
| hn_throawlles wrote:
| classical Vs quantum?
| inasio wrote:
| These guys claimed that they could factor semi-primes in
| polynomial time [0], essentially P == NP. Scott Aaronson
| predictably had some thoughts on that [1]
|
| [0]
| https://pubs.aip.org/aip/cha/article/27/2/023107/135054/Poly...
| [1] https://scottaaronson.blog/?p=2212
| hn_throawlles wrote:
| > "smuggle the exponentiality" somewhere that isn't being
| explicitly considered, exactly like all proposals for
| perpetual-motion machines smuggle the entropy increase
| somewhere that isn't being explicitly considered.
|
| this is the gist of this. so he is saying that the scalability
| issues they will run into, come from the entropy increasing
| with the N such that heat is the real problem? (ah, so maybe
| this is also why Quantum computers are usually frozen???)
|
| also, how big of an N are we talking about?
|
| I see a weird echo here, I am thinking about exporting the
| waste (heat, byproducts, the specific 'how-to? by which, in a
| way, the entropy rules get 'enforced') as being the problem.
|
| so then, he wrote:
|
| > while the proponents wield the sharp steel of accepted
| physical law
|
| I find this analogy quite cutting... with sharp enough steel
| and enough acceptance (regardless of how the acceptance comes
| about.... ok), the heat/entropy can get forced around? time to
| go get my tin foil shield,
|
| then again, I have only been trying to understand
| exponentiation ever since I found out it existed, and I had not
| even heard about the "extended" version of the church-turing
| thesis, hence I'm some kind of ignorant crank (sorry if this
| comes across as bitter, but I am studying a master's degree in
| theory of computer science and I had not ever heard about an
| extended version of that famous thesis;l surely my own fault
| for not going to study to the USA or europe)
___________________________________________________________________
(page generated 2023-05-11 23:01 UTC)