Return-Path: Paul.Field@dcs.qmw.ac.uk Date: Mon, 31 Jan 94 10:32:02 GMT Subject: The Guide Dear Joerg, Being a third year PhD student studying Genetic Algorithms I thought it was about time I knew what they were so I started reading 'The Guide'. I haven't got too far yet - I got a bit sidetracked (Zen Navigation and all that) but I have noticed a couple of little typos that you might like to correct. A1.1, paragraph 3: Reads : ... that admits sexual reproduction (such as budding) ... Should be : ... that admits *a*sexual reproduction (such as budding) ... (amazing what a difference a single letter can make) A1.3, paragraph 5: Reads : ... m (usually a lowercase my, denotes population size ... Should be : ... m (usually a lowercase *mu*, denotes population size ... My natural propensity to become sidetracked with trivial matters has ... hmm, wonder how many breaths a minute I take ? 1,2,3,4,5... sorry. I thought that I could apply to Zen Navigator status, so I have discovered an important question that 'The Guide' does not answer : Are ES individuals like the blindfold pogo-sticking nomads of the Himalayas? The answer, of course, is 'yes'. This question evolved from 'Why does Joerg ask us to imagine a Coke vending machine?' (see A1.3 para.8) the only answer being that it forms the basis of the 'Finite Fizzability' drive that will be developed in Douglas Adams' next book. Some mentally stable people may not understand the question that I have posed, so I have provided some background material on the blindfold pogo-sticking nomads of the Himalayas. I believe that by reading the following story, people will believe that they understand Evolution Strategies without actually doing so and thus will be more knowledgeable than most researchers (me for a start): The story of the blindfold pogo-sticking nomads of the Himalayas. ----------------------------------------------------------------- In the beginning, God randomly generated a number of nomads, blindfolded them, equipped them with pogo sticks and distributed them in the Himalayas. Every year each nomad would bear an offspring which would make a single jump into the unknown in order to find a home. Being blindfold, the nomads had no idea of the best direction to jump so they relied on the teachings of their parents. Some tended to make big jumps North or South, some East or West, some made small jumps and some went North West or South East. In addition to their parents 'wisdom', nomads would listen out for the cries of other nomads and perhaps jump towards them. Wherever a nomad landed it built its home and waited for the dread flood to come. The dread flood was dread, and most nomads agreed that it was a flood too. The skies darkened and in amongst much wailing and gnashing of teeth the great waves enveloped the area sweeping away any foolish enough to live in the foothills. The flood reached different heights each year mysteriously leaving the same number of nomads alive ready to bear offspring and pass on the wisdom of their parents. Naturally enough this wisdom tended to change, especially since youngsters didn't listen to their parents very much (tut, tut. I listened to every word my parents said and obeyed them like a good little boy - honest) but over time the flood acted to select good wisdom. If a Nomad was poorly informed about where to jump then it ended up somewhere low and was washed away in the flood. Even if it got lucky it would pass its bad advice to its offspring and they would be likely to suffer a watery fate. After a time, the nomads, despite being blindfold, had a crude map of the mountains in the form of the advice that they passed on. Unfortunately, when they reached the top of Everest God terminated the run and went away to publish his results. The bizarre similarities between this strange story and Evolution Strategies has only just been noticed: Story ES ----- -- nomads individuals mountains fitness landscape (the higher the fitter) (cliched metaphor) blindfold no knowledge (i.e. derivatives etc) of fitness landscape position of nomad (x,y) Object variables (for more than two imagine a multidimensional mountain range) parental teachings strategy variables (which 'way' = which object variable) jump mutation cries of other nomads recombination (nomads communicate information about their positions i.e. the values of their object variables) the dread flood selection of the fittest kiddies not listening mutation of the strategy variables God Rechenberg, Schwefel ... I submit this material for your consideration. I believe that 'The Guide' should contain hard scientific facts such as I have supplied. Thanks for reading this rubbish, Paul