MullOverThings

Useful tips for everyday

# What is a fitness Valley?

## What is a fitness Valley?

Fitness landscapes are often conceived of as ranges of mountains. There exist local peaks (points from which all paths are downhill, i.e. to lower fitness) and valleys (regions from which many paths lead uphill). A fitness landscape with many local peaks surrounded by deep valleys is called rugged.

## When would the genetic algorithm terminate?

Commonly, the algorithm terminates when either a maximum number of generations has been produced, or a satisfactory fitness level has been reached for the population. A typical genetic algorithm requires: a genetic representation of the solution domain, a fitness function to evaluate the solution domain.

On rugged fitness landscapes, populations may become trapped on a suboptimal fitness peak. It is also possible for a population to discover multiple distinct suboptimal peaks before any single peak genotype has fixed.

## How does fitness change in different environments?

For individuals born in good environmental conditions, mean fitness increases as the adult environment improves. For individuals born in poor environmental conditions, mean fitness may increase weakly (dotted red lines) or decrease (solid red lines) with improvement of the adult environment.

## How to create a good fitness function in genetic algorithms?

How to create a good fitness function? In genetic algorithms, a function called “fitness” (or “evaluation”) function is used to determine the “fitness” of the chromosomes. Creating a good fitness function is one of the challenging tasks in genetic algorithms.

## When does the fitness function become a bottleneck?

If the fitness function becomes the bottleneck of the algorithm, then the overall efficiency of the genetic algorithm will be reduced. The fitness function should quantitatively measure how fit a given solution is in solving the problem. The fitness function should generate intuitive results.

## How to define fitness function for a given problem?

The fitness function should quantitatively measure how fit a given solution is in solving the problem. The fitness function should generate intuitive results. The best/worst candidates should have best/worst score values. How to come up with a Fitness Function for a given Problem?

## Is the design of a fitness function an engineering problem?

The design of a fitness function is an engineering problem, in the sense that you need to think about the solutions you are looking for, and what represents a good and bad solution.