Simplification of mathematical expressions

First version of simplification of expressions.

• Introducting of an algebraic node which holds informations about the algebraic properties of the current node.
• Introducting of an algebra class. Here algebraic properties are stored.
• Transformation functions based on algebraic properties
  • Sorting nodes according to their weight and their name.
  • Lifting of associative operations for example +(a,+(b+c)) = +(a,b,c)
  • Simplification of group identities, for example inv(inv(x)) = x or x * inv( x ) = 1

Benchmark problems for symbolic regression

This release include a lot of benchmark problems, especially for symbolic regression. In detail, the following problems are added

• Koza's quartic, quintic and sextic functions.
• Pagie1 and Pagie2 from "Evolutionary Consequences of Coevolving Targets; Pagie"
• Nguyen 1-10 from "Semantically-based Crossover in Genetic Programming: Application to Real-valued Symbolic Regression; Nguyen et.al."
• Keijzer1-15 from "Improving Symbolic Regression with Interval Arithmetic and Linear Scaling, "Keijzer et. al."
• Korns1-15 from "Accuracy in Smybolic Regression, M. Korns"
• Vladislavleva1-8 from "Order of Nonlinearity as a Complexity Measure for Models Generated by Symbolic Regression via Pareto Genetic Programming, K. Vladislavleva, et. al."

Improved Infrastructure

In this release a lot of infrastructural work has been done:

• Refactoring of trees and enhanced tree interface
• New interface for all IO operations
• Improved documentation
• Setup of continuous integration and improved build system
• Visualization of a genetic algorithm
• Implementation of various fitness calculation methods

Tutorial

First version with examples and tutorials

• Introducing the symbolic regression tutorial
• Introducing the artifical ant example a.k.a. the Santa Fe trail.
• Basic documentation is setup
• Many small fixes.

First test version

First version for simple tests. Changes are

• renaming the library to gpcxx
• moving the library into the master branch
• introducing genetic operators
• first examples and performance tests

Initial version

Very first unstable release. It still lives in the tree_concept branch. The key features is

• Concepts for representation of the tree is finished. It uses cursors and iterators.