Russell K. Standish

OPEN-ENDED ARTIFICIAL EVOLUTION

Of all the issues discussed at Alife VII: Looking Forward, Looking Backward, the issue of whether it was possible to create an artificial life system that exhibits open-ended evolution of novelty is by far the biggest. Of the 14 open problems settled on as a result of debate at the conference, some 6 are directly, or indirectly related to this issue. Most people equate open-ended evolution with complexity growth, although a priori these seem to be different things. In this paper I report on experiments to measure the complexity of Tierran organisms, and show the results for a size-neutral run of Tierra. In this run, no increase in organismal complexity was observed, although organism size did increase through the run. This result is discussed, offering some signposts on path to solving the issue of open ended evolution.

Profit Maximization, Industry Structure, and Competition: A critique of neoclassical theory

Neoclassical economics has two theories of competition between profit-maximizing firms—Marshallian and Cournot–Nash—that start from different premises about the degree of strategic interaction between firms, yet reach the same result, that market price falls as the number of firms in an industry increases. The Marshallian argument is strictly false. We integrate the different premises, and establish that the optimal level of strategic interaction between competing firms is zero. Simulations support our analysis and reveal intriguing emergent behaviors.

Complexity of networks (Reprise)

Network or graph structures are ubiquitous in the study of complex systems. Often, we are interested in complexity trends of these system as it evolves under some dynamic. An example might be looking at the complexity of a food web as species enter an ecosystem via migration or speciation, and leave via extinction. In a previous paper, a complexity measure of networks was proposed based on the {\em complexity is information content} paradigm. To apply this paradigm to any object, one must fix two things: a representation language, in which strings of symbols from some alphabet describe, or stand for the objects being considered; and a means of determining when two such descriptions refer to the same object. With these two things set, the information content of an object can be computed in principle from the number of equivalent descriptions describing a particular object. The previously proposed representation language had the deficiency that the fully connected and empty networks were the most complex for a given number of nodes. A variation of this measure, called zcomplexity, applied a compression algorithm to the resulting bitstring representation, to solve this problem. Unfortunately, zcomplexity proved too computationally expensive to be practical. In this paper, I propose a new representation language that encodes the number of links along with the number of nodes and a representation of the linklist. This, like zcomplexity, exhibits minimal complexity for fully connected and empty networks, but is as tractable as the original measure. ...

Why Occam’S Razor

Ensemble theories have received a lot of interest recently as a means of explaining a lot of the detailed complexity observed in reality by a vastly simpler description “every possibility exists” and a selection principle (Anthropic Principle) “we only observe that which is consistent with our existence.” In this paper I show why, in an ensemble theory of the universe, we should be inhabiting one of the elements of that ensemble with least information content that satisfies the anthropic principle. This explains the effectiveness of aesthetic principles such as Occam’s razor in predicting usefulness of scientific theories. I also show, with a couple of reasonable assumptions about the phenomenon of consciousness, that the linear structure of quantum mechanics can be derived.

NUMERICAL EVIDENCE FOR DIVERGENT BURNETT COEFFICIENTS

In previous papers [Phys. Rev. A 41, 4501 (1990); Phys. Rev. E 18, 3178 (1993)], simple equilibrium expressions were obtained for nonlinear Burnett coefficients. A preliminary calculation of a 32-particle Lennard-Jones fluid was presented in the previous papers. Now, sufficient resources have become available to address the question of whether nonlinear Burnett coefficients are finite for soft spheres. The hard sphere case is known to have infinite nonlinear Burnett coefficients (i.e., a nonanalytic constitutive relation) from mode-coupling theory. This paper reports a molecular dynamics caclulation of the third order nonlinear Burnett coefficient of a Lennard-Jones fluid undergoing color flow, which indicates that this term diverges in the thermodynamic limit.

ClassdescMP: easy MPI programming in C++

ClassdescMP is a distributed memory parallel programming system for use with C++ and MPI. It uses the Classdesc reflection system to ease the task of building complicated messages to be sent between processes.It doesnt hide the underlying MPI API, so it is an augmentation of MPI capabilities. Users can still call standard MPI function calls if needed for performance reasons.

Complexity: Quantity or Quality

The term complexity is used informally both as a quality and as a quantity. As a quality, complexity has something to do with our ability to understand a system or object-people understand simple systems, but not complex ones. On another level, complexity is used as a quantity, when people talk about something being more complicated than another. In this article, the author explores the formalisation of both meanings of complexity, which happened during the latter half of the twentieth century.

Ants Are Not Conscious

Anthropic reasoning is a form of statistical reasoning based upon finding oneself a member of a particular reference class of conscious beings. By considering empirical distribution functions defined over animal life on Earth, we can deduce that the vast bulk of animal life is unlikely to be conscious.

Mechanical Generation of Networks with Surplus Complexity

In previous work I examined an information based complexity measure of networks with weighted links. The measure was compared with that obtained from by randomly shuffling the original network, forming an Erdos-Renyi random network preserving the original link weight distribution. It was found that real world networks almost invariably had higher complexity than their shuffled counterparts, whereas networks mechanically generated via preferential attachment did not. The same experiment was performed on foodwebs generated by an artificial life system, Tierra, and a couple of evolutionary ecology systems, EcoLab and WebWorld. These latter systems often exhibited the same complexity excess shown by real world networks, suggesting that the complexity surplus indicates the presence of evolutionary dynamics. In this paper, I report on a mechanical network generation system that does produce this complexity surplus. The heart of the idea is to construct the network of state transitions of a chaotic dynamical system, such as the Lorenz equation. This indicates that complexity surplus is a more fundamental trait than that of being an evolutionary system.

OpenMP in the field: anecdotes from practice

The High Performance Computing Support Unit at UNSW has a mission to support and encourage the scaling of computationally intensive applications from existing desktop implementations. OpenMP is a good match for this task. This paper reports on several projects in which OpenMP was used to parallelise an application, sometimes successfully, sometimes not so. The interest in these cases is that they are not the usual run of the mill applications that can be parallelised by simplyBadding a few OpenMP compiler directives, but required some lateral thinking.