Linear genetic programming


Linear genetic programming is a particular subset of genetic programming wherein computer programs in a population are represented as a sequence of instructions from imperative programming language or machine language. The graph-based data flow that results from a multiple usage of register contents and the existence of structurally noneffective code are two main differences of this genetic representation from the more common tree-based genetic programming variant.
In genetic programming a linear tree is a program composed of a variable number of unary functions and a single terminal. Note linear tree GP differs from bit string genetic algorithms since a population may contain programs of different lengths and there may be more than two types of functions or more than two types of terminals.

Examples of LGP programs

Because LGP programs are basically represented by a linear sequence of instructions, they are simpler to read and to operate on than their tree-based counterparts. For example, a simple program written in the LGP language looks like a series of instructions separated by a slash:

input/ # gets an input from user and saves it to register F
0/ # sets register I = 0
save/ # saves content of F into data vector D
input/ # gets another input, saves to F
add/ # adds to F current data pointed to by I
output/. # outputs result from F

By representing such code in bytecode format, i.e. as an array of bytes each representing a different instruction, one can make mutation operations simply by changing an element of such an array.