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Avida is an artificial life software platform to study the evolutionary biology of self-replicating and evolving computer programs (digital organisms). Avida is under active development by Charles Ofria's Digital Evolution Lab at Michigan State University and was originally designed by Ofria, Chris Adami and C. Titus Brown at Caltech in 1993. The software was inspired by the Tierra system.

Contents 1 Design principles 2 Use in research 3 See also 4 References 5 External links 5.1 Scientific publications featuring Avida

Tierra simulated an evolutionary system by introducing computer programs that competed for computer resources, specifically processor (CPU) time and access to main memory. In this respect it is similar to core wars, but differs in that the programs being run in the simulation are able to modify themselves, and thereby evolve. Tierra's programs are artificial life organisms.

In Avida, every digital organism lives in its own protected region of memory, and is executed by its own virtual CPU. By default, other digital organisms cannot access this memory space, neither for reading nor for writing, and cannot execute code that is not in their own memory space. Whereas in Tierra the organisms effectively share and compete for one "brain", in Avida each one has its own brain.

A second major difference is that the virtual CPUs of different organisms can run at different speeds, such that one organism executes for example twice as many instructions in the same time interval than another organism. The speed at which a virtual CPU runs is determined by a number of factors, but most importantly, by the tasks that the organism performs: Tasks are logical computations that the organisms can carry out to reap extra CPU speed as bonus.

Adami and Ofria, in collaboration with others, have used Avida to conduct research in digital evolution, and the scientific journals Nature and Science have published several of their papers. Nature' published "The Evolutionary Origin of Complex Features" in 2003, in which the evolution of a mathematical equals operation is constructed of at least 19 simpler, precisely ordered instructions.

• Artificial life
• Digital organism
• Digital organism simulators

• "Testing Darwin", Discover Magazine, February 2005.
• "Computer Speeds Up Evolution, Produces Complexity"
• "Vignere Encoded Text Evolution" from ISCID

• Avida Software - MSU Devolab
• Avida-ED Project - Robert T. Pennock
• An Avida Developer's Site

• R. E. Lenski, C. Ofria, T. C. Collier, C. Adami (1999). Genomic Complexity, Robustness, and Genetic Interactions in Digital Organisms. Nature 400:661-664. abstract of this article
• C.O. Wilke, J.L. Wang, C. Ofria, R.E. Lenski, and C. Adami (2001). Evolution of Digital Organisms at High Mutation Rate Leads To Survial of the Flattest. Nature 412:331-333.
• R.E. Lenski, C. Ofria, R.T. Pennock, and C. Adami (2003). The Evolutionary Origin of Complex Features. Nature 423:139-145.
• S.S. Chow, C.O. Wilke, C. Ofria, R.E. Lenski, and C. Adami (2004). Adaptive Radiation from Resource Competition in Digital Organisms. Science 305:84-86.