Fitness may refer to:
A fitness function is a particular type of objective function that is used to summarise, as a single figure of merit, how close a given design solution is to achieving the set aims.
In particular, in the fields of genetic programming and genetic algorithms, each design solution is commonly represented as a string of numbers (referred to as a chromosome). After each round of testing, or simulation, the idea is to delete the 'n' worst design solutions, and to breed 'n' new ones from the best design solutions. Each design solution, therefore, needs to be awarded a figure of merit, to indicate how close it came to meeting the overall specification, and this is generated by applying the fitness function to the test, or simulation, results obtained from that solution.
The reason that genetic algorithms cannot be considered to be a lazy way of performing design work is precisely because of the effort involved in designing a workable fitness function. Even though it is no longer the human designer, but the computer, that comes up with the final design, it is the human designer who has to design the fitness function. If this is designed badly, the algorithm will either converge on an inappropriate solution, or will have difficulty converging at all.
Fitness is a United States-based women's magazine, focusing on health, exercise, and nutrition. It is owned and published by the Meredith Corporation. The editor-in-chief of Fitness is Betty Wong.
Fitness was launched in 1992, and was acquired by the Meredith Corporation from Bertelsmann's Gruner + Jahr in 2005. In 2005, Fitness also launched its web presence, giving readers separate online resources for fitness and health tips alongside the magazine's monthly editorial content. Betty Wong became Editor-in-Chief in September 2008, incorporating several changes to the magazine, creating several new columns and features. In 2009, Fitness posted significant ad page gains according to the Publishers Information Bureau, increasing by 18.4% when overall magazine publishers' counts were down 27.9% industry-wide. It was recognized for several awards, having been awarded "Most Improved Publication" and best "How-To/Instructional" feature in minOnline's Editorial and Design Awards.