Tuesday, September 27, 2016

Genetic Algorithms

An interesting application of heuristics is something called a genetic algorithm, even though we have yet to talk about these in class (and probably will not), the topic is still very interesting.

It belongs to the evolutionary family of algorithms; meaning that as this algorithm runs it has continuous changes. The way a genetic algorithm works is by having an initial population of possible solutions and each can be represented as a "genome" (this allows for change of the organism). This population also needs to have a way to be evaluated for “fitness” of the genome when compared to the solution. The final ingredient is allowing the population to have a way to change, be it randomly or through interactions. Then by using the idea of mutation on the entire population, you can force evolution of the potential solutions. The population is subject to change iteration by iteration as the algorithm runs. On every new iteration the algorithm attempts to produce a new population that is (possibly) a better fit to the solution. Eventually, if all goes well there will be a solution found deemed to be acceptable set by the algorithms tolerance level. Or, you could simply run out of computation time.

This is particularly good for problems where one might have no idea in what part of the domain the optimal (or acceptable) solution may belong to. By using an initial stochastic distribution of the population throughout a search space, through evolution the algorithm has a higher chance of converging to a local minima/maixima in the solution. It should be noted that this technique is best used when a optimal solution isn’t needed, only one that is good enough to the user. In many cases like that it might be impossible to brute force an optimal solution, or simply take too much time.

Some of the downsides to this method is that the structure of the population and the evaluation method have to be defined by the programmer. Therefore any bias is hardcoded in from the start, and may be missing any crucial connections that weren’t known at the time. Of course, this problem seems to be present in all forms of research and design. Another problem of notice is that they tend to be used in discrete solution sets, looking for a solution. Which is a problem of setting up a finite domain for the solution, some things may not be well formed for this.

This class of algorithm sees great use everywhere, even though some new methods of thinking in evolutionary techniques have risen to prominence over the last decade. It still continues to work very well for many problems. Because, in this algorithms heart it is a optimization technique, so any problem well posed as a function is suited for genetic algorithms. It excels at things like scheduling tasks and financial analysis. It just has a much cooler sounding name then multivariable-optimization.

I think an interesting idea for a final project might be implementing a genetic algorithm. Finding an interesting problem to implement it on is another problem though.

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