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Comment: Re:I thought someone had a glider gun... (Score 3, Informative) 241

by dvgrn (#32610892) Attached to: First Self-Replicating Creature Spawned In Conway's Game of Life

But the Gemini pattern keeps itself going by continuously reconstructing itself, in *spite* of the way the universe normally works.

how so?

I was hoping someone would ask that. Let me start out with a comparison to other cellular automata. Conway's Life is B3/S23 -- "born if 3 neighbors, survives if 2 or 3 neighbors". There are other rules, such as HighLife (B36/S23, very close to Conway's Life) in which a 12-cell pattern can replicate itself -- after 12 generations there are 2 copies, after 36 ticks there are 4 copies, and so on. This pattern regularly evolves from random starting states.

There's even a rule, Fredkin's parity rule (B1357/S1257) where every possible pattern is a replicator -- an extreme example of replication being "just the way the universe works". But these replicators are, in some sense, too simple to be very interesting! They replicate the way crystals grow, and it's hard to harness that kind of low-level behavior. If you wanted a HighLife replicator with 13 cells, or one that would replicate in 13 ticks, instead of 12, you'd be out of luck. By comparison, the Gemini spaceship is extraordinarily adjustable.

will this pattern repair itself if anything happens to it? will it protect itself from outside influences? like a cell wall protects the inside of a cell?

No to all of the above. Conway's Life is not amenable to error-correction of this kind, because small changes have such huge consequences. Kind of like building machinery out of chunks of sub-critical enriched uranium: you can design it so that during normal operation the various pieces never come close enough together to start a chain reaction, but if any little thing goes wrong, you end up with high-energy particles flying all over the place, spreading the reaction to other nearby machinery, which then contributes to the explosion.

so how is it reconstructing itself in spite of the things around it?

Well, I didn't say "in spite of the things around it" -- it was "in spite of the way the universe normally works." The Life universe, for random patterns anyway, normally settles into a scattering of stable or P2-oscillating ash after a few hundred or a few thousand generations. There are any number of "lucky" self-perpetuating stationary and moving patterns that are exceptions to this general rule, but they're all very delicately balanced on the edge of chaos.

how is this anything but a different kind of glider?

The Gemini spaceship contains a large amount of data in its glider channels that is recognizably information about its own structure. Change that data, and the replicator unit will (usually) build something different. Most other gliders and spaceships in Conway's Life don't have anything like this -- all the other hundreds of patterns in Golly's Spaceships folder, or the tens of thousands in Koenig's Life Object database, are "naturally" self-perpetuating, because a future generation of the pattern happens to be identical to the original.

The Gemini spaceship has a significantly higher degree of control over its environment: with the right change to its program, a Gemini replicator unit could construct anything that can be built by colliding gliders, in any empty space in the Life universe. The Gemini contains most or all of the construction tools that a Conway's Life self-replicator will need; it's just a few short steps away from being a true replicator. Mostly it just doesn't have the right program -- yet.

There are a few other large patterns, especially Gabriel Nivasch's Caterpillar, that blur this line to some extent. However, the pi-climber "data" in the Caterpillar is much more difficult to reprogram than the gliders in the Gemini. Several new variants of the Gemini with different speeds and angles of travel have already been built -- with a lot of help from the Python scripts that Andrew Wade made available along with the pattern..

Comment: Re:I thought someone had a glider gun... (Score 4, Interesting) 241

by dvgrn (#32609498) Attached to: First Self-Replicating Creature Spawned In Conway's Game of Life

If I understand correctly, it creates two copies while self-destructing in the process. So it is, indeed, replicating.

Now that's interesting.

When i first read the headline I was befuddled. The whole point of the game is that its structures replicate themselves and create other things all over the map.

But I don't recall ever seeing one that made multiple copies of itself, and then died.

This is a tricky point. The people who say that this new pattern is not ultimately different from a glider are correct, in a sense -- the Gemini spaceship is technically a spaceship, not a replicator.

It _does_ make two copies -- but the copies are of the two replicator units at the ends of the glider channels, not of the entire spaceship.

But replicator units replicating themselves, even with the help of an outside stream of instructions (which is then reflected on to the next newly-created copy of a replicator unit) are still something that hasn't been seen before in the Life universe. So this is a much more impressive technical accomplishment than, say, finding a new variety of spaceship using a search utility.

Gliders and spaceships "replicate" themselves in somewhat the same way that salt crystals or wildfires do -- that's just the way the universe works, you might say. But the Gemini pattern keeps itself going by continuously reconstructing itself, in *spite* of the way the universe normally works.

The replicator units are like robots that include all the tools needed to make more robots exactly like themselves -- but they're radio-controlled and have no internal memory, so you have to pipe the actual construction recipe in from somewhere else. That means they're not self-contained self-replicators, true -- but they're a darn sight closer than a salt crystal or a glider!

Eventually someone will build a pattern with an internal memory that can hold a complete self-construction recipe -- but the Gemini is an important milestone along the way to that goal, and the first true Life replicator will probably contain ideas taken from the Gemini, just as the Gemini contains ideas and mechanisms from preceding patterns.

Comment: Re:Most impressive and important pattern? (Score 1) 241

by dvgrn (#32609332) Attached to: First Self-Replicating Creature Spawned In Conway's Game of Life
All of these patterns -- the Deep Cell, a 512x512 version of the original Unit Life Cell, and several samples of the OTCA metapixel -- are included in the pattern collection that comes with Golly. Check the "HashLife" folder for the metapixel examples, and the "Signal-Circuitry" folder for the others.

There's also a "metafier.py" Python script that lets you convert any selected pattern into an OTCA-metapixel pattern, and then run the results. Shouldn't be attempted on too large a starting pattern -- meta-metacells are a bit too much to ask for, and meta-Gemini-spaceships won't finish building in your lifetime! -- but it's surprising how big a metapattern Golly can handle, once it's been constructed.
Math

First Self-Replicating Creature Spawned In Conway's Game of Life 241

Posted by Soulskill
from the emergent-gameplay dept.
Calopteryx writes "New Scientist has a story on a self-replicating entity which inhabits the mathematical universe known as the Game of Life. 'Dubbed Gemini, [Andrew Wade's] creature is made of two sets of identical structures, which sit at either end of the instruction tape. Each is a fraction of the size of the tape's length but, made up of two constructor arms and one "destructor," play a key role. Gemini's initial state contains three of these structures, plus a fourth that is incomplete. As the simulation progresses the incomplete structure begins to grow, while the structure at the start of the tape is demolished. The original Gemini continues to disassemble as the new one emerges, until after nearly 34 million generations, new life is born.'"
Math

+ - Fast Cellular-Automata Prime Generators and Von Ne->

Submitted by
dvgrn
dvgrn writes "The Golly project (a very fast cross-platform freeware cellular-automaton simulator) now supports up to 256 cell states. Golly 2.1 has just been released on SourceForge, with a pattern library that includes (among many other things) several prime-number generators, using wildly different rulesets from WireWorld to Conway's Life. One pattern starts out with just two ON cells! There are also dozens of constructor and replicator patterns that build copies of themselves or of other patterns; one of these is the first working replicator that uses John von Neumann's original 29-state rule."
Link to Original Source
Science

A New Kind of Science 530

Posted by timothy
from the want-to-have-read dept.
cybrpnk2 writes: "The story is one of epic proportions: Boy genius gets PhD from Cal Tech at age 20, is the youngest recipient ever of the MacArthur Foundation Genius Grant, writes the Mathematica simulation software used by millions of people, makes millions of dollars in the process, becomes enticed by the seductive lure of the Game of Life, and goes into a decade of seclusion to discover the secrets of the universe. You can catch up on the resulting speculation and hype here. The years of anticipation and publication delays came to an end Tuesday, May 14, 2002 with Stephan Wolfram's release of his opus, A New Kind of Science." Read on for cybrpnk2's review of Wolfram's much-heralded work.

This is the theory that Jack built. This is the flaw that lay in the theory that Jack built. This is the palpable verbal haze that hid the flaw that lay in...

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