Tartarus

Abstract: Coevolution is the process of mutual adaptation of two populations. When a difficult optimization is performed with evolutionary computation, a population of adaptive test cases can strongly affect the progress of evolution. This study applies coevolution to the Tartarus task, a grid robot test problem. If the coevolving test cases are viewed as a form of parasite, then the question of virulence becomes an important feature of the algorithm. This study compares different types of parasites for the Tartarus problem. The impact of coevolution in this study is at odds with intuition and statistically significant. Analysis of the different types of coevolution suggests that disruptive crossover has a key effect. In the presence of disruptive crossover, coevolution may need to be modified to be effective. Examples of these modifications are presented. The key method of dealing with disruptive crossover is tracking the age of the Tartarus agents. The age of an agent is defined to be the number of selection steps the agent has survived. Using only older agents to drive coevolution of test cases substantially enhances the performance of one of the two type of coevolution studied.

Abstract: 'H -rot [Lsv 7rpW'statoc Xiocv yeve-r, ouTOap 7rvrot 116 Fat' eU'piCaTepVO, 7tv either (i) one accepts both lines, or (2) one rejects both lines, or (3) one rejects i18 alone, or (4.) one rejects 1i9 alone. The fourth and last named view is represented by only one possible ancient source, to wit Chalcidiusz, is adopted in no recent work, and will therefore be ignored here: the justification for this high-handedness is that the question of most importance for present purposes is whether Tartarus is or is not a separate entity in this cosmogonical passage, and it is obvious that if solution (4) be adopted then Tartarus is not even mentioned. If both lines are to be rejected (solution (2) above), then the same conclusion follows. If one adopts solution (3), then Tartarus is, ,tuX6 xOov6q, manifestly subordinate to Earth, and, whatever the force of the particle -' of I I9, should not be taken as a separate entity on a par with Earth and Eros. It is probable that the same conclusion should be drawn from solution (i), the acceptance of both the disputed lines; but not all critics would necessarily agree with this view, and it may therefore be useful to give the question another airing. The indirect tradition for the text is instructive, but not probative.3 Schwabl4 has recently pointed out that the older ancient authorities differ from the younger, except their followers, not certainly in text, but either in text or in interpretation. Acusilaus, Platos and Zeno of Citium6 may either have adopted the rendering of Schoe-

Abstract: 1. Bartleby, the Scrivener 2. Cock-A-Doodle-Doo! 3. The Fiddler 4. The Paradise of Bachelors and the Tartarus of Maids 5. The Lightning-Rod Man 6. The Encantadas, or Enchanted Isles 7. Benito Cereno 8. I and My Chimney 9. Billy Budd, Sailor (An Inside Narrative)

Abstract: This paper examines the use of very small (4-7) population sizes in genetic programming. When using exploitive operators, this results in hillclimbing; when using exploratory operators this results in genetic drift. The end result is a different way of searching the space which gives insight into the fitness landscape and the nature of the variation operators used. This study compares the use of very small population sizes with the use of population sizes up to 1000 for three genetic programming problems: 4-parity using parse trees, Tartarus using ISAc lists, and several versions of plus-one-recall-store (PORS) using parse trees. For 4-parity and Tartarus with 60 ISAc nodes, algorithms with very small population sizes found more solutions faster. For PORS, the effect was less pronounced: more solutions were found, but the algorithm was faster only than when using slightly larger populations. For Tartarus with 30 ISAc nodes, no effect was detected.