Q1: What are Evolutionary Algorithms (EAs)?

     Evolutionary algorithm is an umbrella term used to describe computer-
     based problem solving  systems  which  use  computational  models  of
     evolutionary   processes   as   key  elements  in  their  design  and
     implementation.  A  variety  of  evolutionary  algorithms  have  been
     proposed.   The  major  ones  are:  GENETIC  ALGORITHMs  (see  Q1.1),
     CLASSIFIER  SYSTEMs  (see  Q1.4), and GENETIC PROGRAMMING (see Q1.5).
     They all share a common conceptual base of simulating  the  EVOLUTION
     of  INDIVIDUAL  structures  via processes of SELECTION, MUTATION, and
     REPRODUCTION.  The processes depend on the perceived  PERFORMANCE  of
     the individual structures as defined by an ENVIRONMENT.

     More  precisely, EAs maintain a POPULATION of structures, that evolve
     according to  rules  of  SELECTION  and  other  operators,  that  are
     referred  to  as  "search operators", (or GENETIC OPERATORs), such as
     RECOMBINATION  and  MUTATION.   Each  INDIVIDUAL  in  the  population
     receives  a measure of it's FITNESS in the ENVIRONMENT.  REPRODUCTION
     focuses attention on high fitness individuals, thus  exploiting  (cf.
     EXPLOITATION)  the  available fitness information.  Recombination and
     mutation perturb those individuals, providing general heuristics  for
     EXPLORATION.  Although simplistic from a biologist's viewpoint, these
     algorithms are sufficiently complex to provide  robust  and  powerful
     adaptive search mechanisms.

     --- "An Overview of Evolutionary Computation" [ECML93], 442-459.

     Algorithm EA is

	  // start with an initial time
	  t := 0;

	  // initialize a usually random population of individuals
	  initpopulation P (t);

	  // evaluate fitness of all initial individuals in population
	  evaluate P (t);

	  // test for termination criterion (time, fitness, etc.)
	  while not done do

	       // increase the time counter
	       t := t + 1;

	       // select sub-population for offspring production
	       P' := selectparents P (t);

	       // recombine the "genes" of selected parents
	       recombine P' (t);

	       // perturb the mated population stochastically
	       mutate P' (t);

	       // evaluate it's new fitness
	       evaluate P' (t);

	       // select the survivors from actual fitness
	       P := survive P,P' (t);
     end EA.
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