

Probability Chip - eli_s
http://www.technologyreview.com/computing/26055/?a=f

======
tricky
The thesis on which this is based:

<http://phm.cba.mit.edu/theses/03.07.vigoda.pdf>

edit: p 135 is where he starts talking about implementation in silicon

~~~
sedachv
Here's a nice presentation from him that has diagrams of how the basic logic
circuits are built up using this approach:

<http://cba.mit.edu/presentations/03.09.Vigoda.ppt>

------
moultano
I'm curious how they deal with probabilities very close to 1 or 0. Usually
when people are doing bayesian things with probabilities they work in logistic
space so that the precision of values close to 1 or 0 is effectively
unbounded. That seems like a hard thing to do with an analog circuit.

~~~
wwalker3
The founder's thesis mentions that they use a linearizer in their analog
circuit, but all that does is give the same precision over the entire logical
value range from 0 to 1 (by that I mean the same amount of voltage swing
equals the same amount of "logic value change" anywhere in the range).

I suppose they could use a "non-linearizer" to put more of the precision near
0 and 1, but it would come at the expense of precision in the middle. The less
voltage swing is involved, the more susceptible you are to noise from various
sources.

------
xtacy
Is it likely (in the future) to see more domain specific chips? Something like
what <http://www.deshawresearch.com/> has created---a custom chip Anton,
optimised for Molecular Dynamics simulations.

~~~
gwern
Domain-specific chips is a cyclical trend. They come and go; at some times
they have advantages, and at others they don't. (Remember Lisp machines? Good
initially but vastly outperformed by the end of their lifespan.) See for
example the classic 'wheel of reincarnation' paper on graphics:
[http://cva.stanford.edu/classes/cs99s/papers/myer-
sutherland...](http://cva.stanford.edu/classes/cs99s/papers/myer-sutherland-
design-of-display-processors.pdf)

The fundamental problem as I see it is that any domain-specific chip will
receive a tiny fraction of R&D and economies of scale and amortization that a
general purpose one will, and so its advantage is only temporary. As long as
Moore's law is operating, this will be true.

~~~
gwern
To quote the thesis on probabilistic chips:

> In practice replacing digital computers with an alternative computing
> paradigm is a risky proposition. Alternative computing architectures, such
> as parallel digital computers have not tended to be commercially viable,
> because Moore’s Law has consistently enabled conventional von Neumann
> architectures to render alternatives unnecessary. Besides Moore’s Law,
> digital computing also benefits from mature tools and expertise for
> optimizing performance at all levels of the system: process technology,
> fundamental circuits, layout and algorithms. Many engineers are
> simultaneously working to improve every aspect of digital technology, while
> alternative technologies like analog computing do not have the same kind of
> industry juggernaut pushing them forward.

------
perplexes
One step closer.
[http://en.wikipedia.org/wiki/Technology_in_The_Hitchhiker%27...](http://en.wikipedia.org/wiki/Technology_in_The_Hitchhiker%27s_Guide_to_the_Galaxy#Infinite_Improbability_Drive)

~~~
chime
There's a single-quote missing in your link after Hitchhiker and before the
letter s: <http://en.wikipedia.org/wiki/Technology_in_The_Hitchhiker> \+ ' +
s_Guide_to_the_Galaxy (looks like HN comment filters it out)

~~~
perplexes
Thanks!

------
snippyhollow
My Ph.D advisor will go crazy, he had his European research project on a
probability computer turned down a few months ago.

~~~
andraz
wouldn't starting just 6 months ago be a bit late in any case?

------
api
Isn't this just the revenge of the analog computer?

Not saying it's a bad idea... I'm really for the idea of revisiting
assumptions in computer design.

~~~
copper
Sure, if you can represent your problem using probabilities :)

That said, I'm more excited about the use of Lyric's technology in ECC memory.
I'm skimming through Vigoda's thesis, and it seems that another _very_
interesting application ought to be making even lower-power mobile backend
chips.

------
ajb
I thought I'd heard something like this before. From 2004:
<http://www.eetasia.com/ART_8800354714_499488_NT_92255b4a.HTM>

That's a turbo decoder rather than a generic probability calculator, but it's
doing probability calculations in the analog domain.

This sort of thing may make sense for error correction, but I don't think
people will run general probability calculations on it. Too difficult to debug
:-)

Though, I do wonder if they can simulate a neuron more efficiently than
digital logic.

------
RiderOfGiraffes
Sounds a lot like the ByNase protocol that Ward Cunningham (inventor of the
wiki) came up with:

<http://c2.com/cybords/wiki.cgi?BynaseProtocol>

------
RiderOfGiraffes
Printer friendly, (almost) no ads, no pointless images:

[http://www.technologyreview.com/printer_friendly_article.asp...](http://www.technologyreview.com/printer_friendly_article.aspx?id=26055&channel=computing&section=)

~~~
perplexes
Looks like they check the referrer and redirect you to the original article :(

~~~
RiderOfGiraffes
Sneaky swine ...

------
siavosh
similar to the fuzzy-logic chips of the 90's?

------
frisco
How does this compare to what Navia Systems is working on?

------
jon_hendry
But how do you connect it to the cup of no tea?

