Chris_Langton@UMICH-MTS.MAILNET (02/19/86)
From: Chris_Langton%UMich-MTS.Mailnet@MIT-MULTICS.ARPA
I read in the ailist a series of comments on the size of self-reproducing
systems (ARPA.AIList, Volume 3, Issue 71, 06/01/85 - starting with the
message from zim@mitre of 05/24/85 )
I have published an article wherein I exhibit a self-reproducing configuration
embedded in a cellular automaton which occupies a mere 10x15 cell rectangle.
The construction is based on a modification of one of Codd's components
(see Codd: Cellular Automata) in his simplification of von Neumann's
self-reproducing machine. My article is published in: Physica 10D (1984)
North Holland, pp 135-144, entitled 'self-reproduction in cellular automata'.
Basicly, this configuration consists of a looped pathway with a construction
arm extending out from one corner. Signals cycling around the loop cause
the construction arm to be extended by a certain amount and then cause a
90 degree corner to be built. as this sequence is executed 4 times (due
to the same signal sequence cycling around the loop 4 times), the four
sides of an offspring loop are built. When the extended construction arm
runs into itself, the resulting collision causes the two loops to detach
from each other and also triggers the construction of a new construction
arm on each loop. The new arm on the parent loop is located at the
next corner 'downstream' (in the sense of signal flow) from the original
site. Thus, the parent loop will go on to build another loop in a new
direction. Meanwhile, when the offspring was formed, a copy of the signal
sequence that serves as the description was trapped inside it when the
two detached from one another, thus it, too, goes on to build offspring.
The result is a growing colony of loops that expands out into the array,
consisting of a reproductive outer fringe surrounding a growing 'dead'
core, in the manner of a coral reef or the cross section of a tree.
Details are to be found in the article. Although this construction is
not capable of universal construction or computation, it clearly
reproduces itself in a non-trivial manner, unlike the reproduction under
modulo addition rules, of which Fredkin's reproducing system is an example.
I am also working on cellular automaton simulations of insect colonies and
artificial biochemistries. I have another article coming out in the proceedings
of the conference on 'Evolution, Games, & Learning' held at the Los Alamos
National Labs last May. It is entitled 'studying artificial life with cellular
automata'. There will be a video tape available soon from Aerial Press in
Santa Cruz which illustrates the self-reproducing loops as well as the
artificial insect colony simulations and other examples of `artificial life'.
I would be very interested in hearing from anybody who is working on anything
which might fall under the general heading 'artificial life'. I would also
like to try to get together a workshop, with computer support, where people
who have been working in this area could get together and have a 'jam session'
of sorts, and see each other's stuff. Any proceedings from such a workshop
would benefit greatly from having a video published along with it. If anybody
is interested in helping to organize such a workshop, send me a message. I
can be reached at: CGL%UMICH-MTS@MIT-MULTICS.ARPA
USPS: Christopher G. Langton / EECS Dept. / University of Michigan /
Ann Arbor MI 48109
MA-BELL (now divorced from PA-ATT) 313-763-6491