announce.313

地球模拟器

       1, not zero (thus creating a "flag" value that can specifically
       and easily be tested for by a tierran creature).
    2) selection pressure (via the slice size) for medium size        
       creatures (256 to 5K instructions in size) (gaussian
       distribution of slice size around a mean creature size
       of about 2K)
    3) memory protect bits turned on, and used in a significant fashion.
    4) a more complex ancestor, although the copy code is almost
       identical to Ray's 80aaa.

     An adaptation which evolved under these conditions is the first example
I know of in which a Tierran creature evolved a decision making mechanism.
If memory is not available when a creature requests it, the memory allocator
returns a value of zero in the AX register, rather than the address of the
allocated block.  The adaptation then, is to somehow move the value in the
AX register into CX (for example by first pushing AX onto the stack and then
popping that value into the CX register).  Then the creature executes if_cz,
which tests to see if the CX register is zero.  If CX is not zero, the
creature proceeds with reproduction, if CX is zero the creature executes some
code which leads to making another request for memory rather than trying to
copy the genome without having a cell to copy it into.  Paul provided the
following details:

    I recall seeing both:

        mal       ;  111
        push_ax   ;  111
        pop_cx    ;  111
        if_cz     ;  111

    as well as the slightly more expensive:

        mal        ; 111
        mov_ab     ; 111 
        push_bx    ; 111
        pop_cx     ; 111
        if_cz      ; 111

14) Future Phylogeny

     At the moment, the primary effort in new code development is dedicated
to an extension to the genebanker that will produce an ironclad phylogeny.
The requires that we trace the genetic source of every instruction written
into every creature.  Stay tuned.

15) Tierra Funding

     The National Science Foundation has awared a Small Grant for Exploratory
Research to Dr. Ray to support the Tierra project.  The grant is titled:
``Computer Architectures for the Natural Evolution of Machine Code''.  It
is jointly funded through the Computer Systems Architecutre program and the
Computational Biology Activities programs.

16) Tierra in the News

The Tierra Simulator has been widely reported in the media.  Below is a
list of most of the national or international reports that I am aware of.
If you know of some news report not on this list, please send me a hard
copy.

Nature (John Maynard Smith, UK) February 27, 1992: ``Byte-sized evolution.
...we badly need a comparative biology.  So far, we have been able to study
only one evolving system and we cannot wait for interstellar flight to
provide us with a second.  If we want to discover generalizations about
evolving systems, we will have to look at artificial ones.  Ray's study is a
good start.''

Nature (Laurence Hurst & Richard Dawkins, UK) May 21, 1992:
``Life in a test tube.''

New York Times (Malcolm Browne, USA) August 27, 1991: ``Lively Computer
Creation Blurs Definition of Life.  Software forms, obeying Darwin's rules,
vie to avoid the `reaper'.''

Science News (John Travis, USA) August 10, 1991: ``Digital Darwinism:
Electronic Ecosystem.  Evolving `life' flourishes and surprises in a
novel electronic world''.

Scientific American (John Rennie, USA) January 1992: ``Cybernetic Parasites...
Tierra... has been hailed as the most sophisticated artificial-life program
yet developed...''

New Scientist (Roger Lewin, UK) February 22, 1992: ``Life and death in a
digital world.  No one can turn back the evolutionary clock, but we can
follow the fate of a rich menagerie of artificial organisms as they evolve
in a model world.''

The Economist (Anon, UK) January 4, 1992: ``The meaning of `life'.
In order to understand the origin of life, scientists are switching from the
chemistry set to the computer.  In the process, they are beginning to
understand what it means to be alive.''

Guardian (Jocelyn Paine, UK) January 9, 1992: ``Unravelling the loop in the
primordial soup.  Tierran machine code is so adaptable it survives.  Jocelyn
Paine charts the evolution of artificial life within the computer.''

Actuel (Ariel Kyrou, France) April 1992: ``Visite Guidee Aux Extremes De
La Science: La Vie Artificielle.  Etes-vous pr\^{e}ts \`{a} entrer dans
l'univers vertigineux de la vie artificielle?  Un champ scientifique tout neuf
sur lequel se penchent les grosses t\^{e}tes et les Nobel de labos
am\'{e}ricains.''

The Chronicle of Higher Education (David Wilson, USA) December 4, 1991:
``Approaching Artificial Life on a Computer.  Survival-of-the-fittest
electronic organisms dramatically illustrate Darwinian principles.''

Mikrobitti (Pekka Tolonen, Finland) November 1991: ``Olemmeko humanoiden
biologinen koe?  Tierra simuloi el\"{a}m\"{a}\"{a}.''

Europeo (Giovanni Caprara, Italy) September 1991: ``Anche il computer ha
fatto un figlio.  Un biologo americano ha creato un software capace di
elaborare programmi che si evolvono da soli.''

GenteMoney (Riccardo Orizio, Italy) November 1991: ``Cos\`{\i} ho dato
la vita al software.''

Computerworld (Michael Alexander, USA) September 30, 1991: ``Tierra adds to
evolutionary studies.  A computerized world created on an IBM PC could
have real-world benefits for scientists.''

Sueddeutsche Zeitung (Konrad Peters, Germany) October 21, 1991:
``Die Evolution im Computer.  `K\"{u}nstliches Leben' hilft Biologen und
Informatikern auf die Spr\"{u}nge.''

Super Interessante (Anon, Brazil) November 1991: ``A vida dentro do
computador.''

Technology Review (Susan Scheck, USA) April 14, 1991: ``Is It Live Or Is
It Memory?''

Corriere Della Sera (Giovanni Capara, Italy) August 28, 1991: ``Pronto in
USA il programma che si riproduce.  Il computer `padre' crea vita
informatica.''

Fakta (Tom Ottmar, Norway) March 1992: ``Den Lever!  En `skabning', der
best\aa r af nuller og \'{e}nere, er vokset ud af indamaden p\aa \ en
computer og er blevet en videnskabelig sensation i USA.''

Associated Press (Theresa Humphrey, USA) October 1991: ``Bringing life to
computer.  U of D biologist's program is self-replicating, shows evolution.''

Hovedomr\aa det (Jakob Skipper, Denmark) December 6, 1990: ``Kunstigt liv.
Nu kommer det kunstige liv.  En voksende gruppe af dataloger, biologer,
fysikere, psykologer og mange andre forskere efterlinger p\aa \ computer
det naturlige liv.''

17) Tierra Publications

Ray, T. S.  1991.  ``Is it alive, or is it GA?''
Proceedings of the 1991 International Conference on Genetic Algorithms,
Eds. Belew, R. K., and L. B. Booker, San Mateo, CA: Morgan Kaufmann, 527-534.

Ray, T. S.  1991.  ``An approach to the synthesis of life.''
Artificial Life II, Santa Fe Institute Studies in the Sciences of
Complexity, vol. XI, Eds. Farmer, J. D., C. Langton, S. Rasmussen, &
C. Taylor, Redwood City, CA: Addison-Wesley, 371-408.

Ray, T. S.  1991.  ``Population dynamics of digital organisms.''
Artificial Life II Video Proceedings,  Ed. C.G. Langton,
Redwood City, CA: Addison Wesley.

Ray, T. S.  1991.  ``Evolution and optimization of digital organisms.''
Scientific Excellence in Supercomputing: The IBM 1990 Contest Prize
Papers, Eds. Keith R. Billingsley, Ed Derohanes, Hilton Brown, III.
Athens, GA, 30602, The Baldwin Press, The University of Georgia.

18) Mailing Lists

     There are two mailing lists for Tierra users.  The first list is for
people who only want to get the official announcements, updates and bug-fixes.
The other will carry the official postings, and are intended for discussion
of Tierra by users.  This one is distributed in digest form, when there is
enough material.  The lists are:

tierra-announce    official updates, patches and announcements only
tierra-digest      discussion, updates, etc. (digest form)

The addresses are: 

[e-mail]   the list administrator (Tom Uffner). to
                                    be added, removed, or complain about
                                    problems with any of these lists.

[e-mail]    to post to the list.

[e-mail]       for bug-reports or questions about the
                                    code or installation.

     You may also be interested in the Artificial Life mailing list.
Subscribe to the list by sending a message to:

[e-mail]

     Post to the list by sending a message to:

[e-mail]

19) What Tierra Is

     The C source code creates a virtual computer and its operating system,
whose architecture has been designed in such a way that the executable
machine codes are evolvable.  This means that the machine code can be mutated
(by flipping bits at random) or recombined (by swapping segments of code
between algorithms), and the resulting code remains functional enough of the
time for natural (or presumably artificial) selection to be able to improve
the code over time.

     Along with the C source code which generates the virtual computer, we
provide several programs written in the assembler code of the virtual
computer.  One of these was written by a human and does nothing more than make
copies of itself in the RAM of the virtual computer.  The others evolved from
the first, and are included to illustrate the power of natural selection.

     The operating system of the virtual computer provides memory management
and timesharing services.  It also provides control for a variety of factors
that affect the course of evolution: three kinds of mutation rates,
disturbances, the allocation of CPU time to each creature, the size of the
soup, etc.  In addition, the operating system provides a very elaborate
observational system that keeps a record of births and deaths, sequences
the code of every creature, and maintains a genebank of successful genomes.
The operating system also provides facilities for automating the ecological
analysis, that is, for recording the kinds of interactions taking place
between creatures.

     This system results in the production of synthetic organisms based on
a computer metaphor of organic life in which CPU time is the ``energy''
resource and memory is the ``material'' resource.  Memory is organized into
informational patterns that exploit CPU time for self-replication.  Mutation
generates new forms, and evolution proceeds by natural selection as different
genotypes compete for CPU time and memory space.

     Diverse ecological communities have emerged.  These digital communities
have been used to experimentally examine ecological and evolutionary
processes: e.g., competitive exclusion and coexistence, host/parasite density
dependent population regulation, the effect of parasites in enhancing
community diversity, evolutionary arms race, punctuated equilibrium, and the
role of chance and historical factors in evolution.  This evolution in a
bottle may prove to be a valuable tool for the study of evolution and ecology.