Showing posts with label genetic algorithm. Show all posts
Showing posts with label genetic algorithm. Show all posts

Sunday, May 25, 2014

Genetic Programming vs Genetic Algorithms


Genetic Programming vs Genetic Algorithms 
The genetic algorithm has several disadvantages, for example the length of the strings
are static and limited, it is often hard to describe what the characters of the string means
and the meaning of the characters is limited to whatever they are specified to be. These
problems could perhaps be overcome but a better solution brings back the original
question: How can computers learn to solve problems without being explicitly
programmed? Genetic programming suggests the following solution: simply apply the

genetic operations on computer programs to evolve better and better programs.


There are a lot of frameworks that you can start with Genetic Programming immediately however you do not need them to start using Artificiell Intelligence. You simply need to know about a few core knowledge to solve problems like Traveling Salesman Problem known as TSP in computer world.


Selection in Genetic Algorithm
There are different methods to select chromosomes from a population to be parents for crossover to next generation.

Roulette wheel selection


Boltzman selection
Tournament selection
Rank selection
Steady state selection


Crossover and Mutation Probability
This is two parameters of Genetic Algorithms.
Crossover takes place once the chromosomes are selected based on one of the methods above.
This will produce offsprings. A crossover of 100% or 1.0 means that all of the chromosomes will be used for reproduction, i.e. there is no servivors. Empirical studies shows that a Crossover probability of between 0.65 and 0.85 will achieve better results.If it is 0% nothing is changed and the offspring is a exact copy of one of the parent.
Some researchers recommend decreasing the cross-over probability and increasing the mutation probability in depending on the number of performed generations. Others say that it is good if the genetic algorithm has a dynamic cross-over probability that changes in dependence to spread value inside the selection mechanism.

Resources:
http://en.wikipedia.org/wiki/Genetic_algorithm


Sunday, May 11, 2014

Methods to find suitable solution (ie. not necessarily the best solution),

Finding best Solution in Computer Science

There are methods to find solutions that is not necessarily best solution, but can find a best possible solution in a Serach Space (i.e. the space of all feasible solutions).
There are problems that can not be solved by traditional way and such problems are called NP-problems.
Problems that can not be solved in polnomyal time is such problems that need another way to solve problems. NP stands for Non-determinsitic polynomial and we can only "guess" a solution and then check the solution.Nobody today knows if there is fast exact algorithm. Proving or disproving this is a task for future reseracher. To find such algorithm today they use the following methods and Genetic Algorothm is one of them.

Hill climbing
Tabu search
Simulated annealing
Genetic algorithm


Look at Wikipedia to find out more about the finding solutions.