Modular Robots

levin writes "An article in the latest issue of IEEE spectrum discusses modular robots--robots made of small, identical components or modules. These robots can slither, roll like a tank tread, inchworm, or crawl like a spider. The idea is that modular robots will be not only cheaper to build because the modules are all the same, but will be more able to repair themselves (by shedding damaged modules). Even cooler, each of the 5cm cube modules in Xerox PARC's polybot sports its own PowerPC 555 and 1mb ram."

Comments

Ack! Replicators!

[RandomCoil]

I don't think making these things is such a good idea. TV has taught us that they will eventually take over a Russian submarine and almost destroy Thor's home world.

What, you didn't see "Small Victories" from the fourth season of Stargate SG1?

Spliting and Merging

[regen]

Something that they really don't talk about in the article is spliting and merging robots. They talk about reconfiguration of a single robot, but I think spliting and merging with a group of robot would be very interesting.

Imagine a robot being able to break a portion of itself off and send it to perform a sub task. Imagine two robot getting together to cooperate on a task by combining and spliting apart again once the task was completed.

off-topic. (not goatsx, please don't censor to -1)

[Anonymous Coward]

These are robots, not computers.
But imagine what you could do with a 5 cm^3 computer if it were a self-powered cube that could automatically share number-crunching resources with any other cube it got connected with.
Specifically, I address in this off-topic post the feasability of simulating the human brain with current technology.
Before we start, see here for the statistics I am using.
Note especially that:

1. the brain runs at a MAXIMUM of 2,000 Hz in any given part of it. (A neuron cannot fire more frequently).
   
2. There are 20,000,000,000 (twenty u.s. billion) Neurons in the adult brain. (With an upper bounds of 50 ubillion in some estimates.).
   
3. Each neuron is connected to 2,000-5,000 other neurons.
   
4. The greatest frequency with which an individual neuron can fire is 250-2000 hertz. (Estimates vary).
   

I'll now interpret this information.
Let's posit for a second (wrongly) that a five hundred megahertz computer ("PowerPC 555" in article, though again the article refers to robots, not mere number-crunching computers) could simulate with each hertz all that a neuron does in one firing. (By contrast, a typical "hertz" in today's gigahertz computers is less than required to retrieve two thirty-two bit numbers, add them, and store the result.)
With this assumption, we'd only need (upper estimate) 200,000 such processors [1] to simulate the brain real-time.

200,000 * 5 cubic centimeters (size of these suckers) is 1,000,000 cubic centimeters, or 100 centimeters to each side of a cube, which is 1 cubic meter.
That's not very big at all, and even if these robots cost $2,000 each, 200,000 of them would only cost $400 million.
The problem, of course, is that no way one hertz on these babies is going to simulate all that a neuron does, even on average, since each neuron is connected to up to 5,000 other neurons, and has a small interaction with each one each time it fires.
Since a 32-bit integer can enumerate ("address") just over 4 billion items, we would need an integer and another byte (we'd only use half) to address each of the other 50 billion neurons. In other words, just to pass information about which current connection we're looking at we need to handle two 4-byte integers and another byte on each end of your dendrite (connector and connectee). If we assume that an "interaction" between two neurons, when one of them fires, takes a hundred real hertz to process (I think this is fair, since the amount of logical information that a neuron stores can be represented by two or three variables, which you'd read, compare, see if a threshold is met, then store), then we'd need not one hertz per neuron but 100 hertz * 5000 dendrites (connections to other neurons with which it transacts). Our 1 cubic meter has just jumped to 500,000 (five cubic kilometers), and our $400 million price-tag has just jumped to $20 trillion.
But $20 trillion will buy you the processing power (not necessarily the io bandwidth) to process as much as the human brain can possibly, ever process, if every neuron is connected to as many other neurons as it possibly can, and each one is firing as much as it biologically can, by the highest estimate anyone estimates, and is connected to as many other neurons as anyone estimates is possible.
Needless to say, your actual costs for doing as much processing as the human brain processes are much, much lower.
Why, if you take simply the fact that the max hertz we calculated as 2000, whereas the "max" is 250-2,000, and the "average" by most estimates is around 20 hertz (a neuron, on average, will not fire more than twenty times a second), you've just reduced your processing time by a factor of 100, going from $20 trillion back down to $200 billion.
Now let's look at the difference between the "processing" that we said we can buy for $2000 (500 megahertz) and the io bandwidth we need.
We estimated 100 hertz per neuron interaction with another neuron, and we said that a neuron was connected with 5000 other neurons, and that the "state" of each connection could be represented (logically) by three 32-bit integers (four bytes each) and another 5 bytes just to address the second neuron, we now need 8 bytes * 5,000 neurons available over the timespan of 100 hertz, where we're looking at a 500 megahertz computer. This means that to get the io bandwidth over one second, we multiply these eight bytes by 5,000,000 (the quotient of 500 megahertz and 100 hertz), and get 40 million / 1024*1024 = 38.14 megabytes/second.
If we forget about the 5-cm cubes (and any semblance of topicality) this actually isn't so unreasonable, since a $2000 computer needing only 500 megahertz shouldn't have any problem with 38.13 megs/second. Or 4 gigs of RAM.
Anyway, let me know where my numbers are off, but it seems I've concluded that, today, $200 billion will buy you everything you need to simulate a human brain real-time, without any compression or special optimization.
So then next time somebody says: "Computer will never think, because only human can think." You can proudly answer:
"Shut your face, ignorant person. Soon as we figure out all the laws of neural interaction and find a way to image someone's brain, $1.57 billion dollars will buy you all the computer processing you need to simulate that brain real-time. [10.5 years from now, or 7 Moore's law iterations -- I divided $200 billion by two to the seventh]. But, of course, if ten and a half years to you is longer than "never", then feel free to remain ignorant, moron."

ac.
of course, I've been known to be wrong. please correct me gently.
[1] this is 50 billion divided by 250,000, since 500 megahertz is 250,000 more frequent than 2,000 hertz.