
Computer Scientists Build Computer Using Swarms of Crabs - Technology Review - sakai
http://www.technologyreview.com/blog/arxiv/27730/?ref=rss
======
richardk
The title seems pretty misleading: it seems they only built an AND and an OR
gate, I wouldn't really call a couple of logic gates a _Computer_.

Still, building logic gates using crabs, very good. :)

------
wdewind
It takes the author to the end of the piece to admit that no, in fact, they
did not build a computer using swarms of crabs. Right after he admits it's
false he, he asserts it is true again...really...link baity bad writing for an
MIT blog.

 _"To be fair, the results were mixed. While Gunji and co found they could
build a decent OR gate using soldier crabs, their AND-gate was much less
reliable.

However, it's early days and they say it may be possible to produce better
results by making conditions inside the computer more crab-friendly. (No crabs
were harmed in the making of their computer, say Gunji and co.)

So there you have it--a computer in which the information carriers are
swarming balls of soldier crabs."_

------
Tichy
I know what I'll be building next time I visit the sea side. No more sand
castles...

------
noonespecial
Somewhere Charlie Stross is smiling widely.

------
betawolf33
"The first is theoretical--ordinary computers are hugely energy inefficient--
some eight orders of magnitude worse than is theoretically possible. "

Eh? Is this saying that ordinary computers are eight orders of magnitude more
energy-inefficient than the maximum possble inefficiency?

Oh, wait, they mean the other possibility.

Also, as others mention, they only build two gates, and one of them doesn't
work very well.

------
dsrguru
I'm waiting for the NAND or NOR gate...

~~~
lolcraft
The NOT gate might be difficult to build ;)

~~~
jws
They claim to have built it already, and given that the AND gate is actually a
tripartite output of a∧¬b, a∧b, ¬a∧b the NOT seems to be trivial.

Note: this is not level based logic, but billiard ball logic. If I understood
that better I'd write a concise, illuminating explanation of why ¬a∧¬b is
missing in the AND gate's outputs.

<http://en.wikipedia.org/wiki/Billiard_ball_computer>

~~~
endtime
Uh, I think you're overthinking this. What is the output of a NOT crab-gate
when there are no crabs in the input?

~~~
premchai21
In a billiard-ball model one would construct a NOT/inverter with a crab source
that normally flows straight to the output but can be misdirected into a drain
by crabs coming in from the input. Of course you need a crab source for this,
but this is little different from electronic transistor-based computers, where
the inverse of Vss is Vdd and the Vdd comes from the power supply.

~~~
endtime
Right, yes, but the (semi-serious) point is that we don't have a crab grid in
the same way we have a power grid, so actually implementing this (which is
what the article is about, rather than just theory) might be hard. For the
crab computer to "run" arbitrary computations it would need an arbitrarily
large source of crabs.

~~~
jws
A functional crab computer would probably have to be built from delay
insensitive logic[1]. The outputs of the gates would be of the form X and !X,
where the signal (crab cluster) would appear at the appropriate output.

With regards to crab supply, I think the sufficient study of reversible
computing, and in particular their charge conservation properties, would
address that.

You'll still have to have a mechanism to spray bits of dead fish around to
feed the thing.

\--

[1] <http://en.wikipedia.org/wiki/Delay_insensitive_circuit>

[2] <http://en.wikipedia.org/wiki/Reversible_computing>

