Harmony search (HS) is a metaheuristic algorithm (also known as soft computing algorithm or evolutionary algorithm) mimicking the improvisation process of musicians. A metaheuristic is a Heuristic method for solving a very general class of computational problems by combining user-given black-box procedures €”usually heuristics Soft computing refers to a collection of computational techniques in Computer science, Machine learning and some engineering disciplines which study model and analyze In Artificial intelligence, an evolutionary algorithm (EA is a Subset of Evolutionary computation, a generic population-based Metaheuristic In the process, each musician plays a note for finding a best harmony all together. Likewise, each decision variable in optimization process has a value for finding a best vector all together.
The algorithm
Harmony search tries to find a vector x that minimizes some cost function.
The algorithm as given by [2] is:
- Initialize the harmony memory: pick k random vectors
.
- Make a new vector x'. For each component x'i:
- with probability phmcr pick the component from memory,

- with probability 1 − phmcr pick a new random value in the allowed range.
- Pitch adjustment: For each component x'i:
- with probability ppar change x'i by a small amount,
.
- with probability 1 − ppar do nothing.
- If x' is better than the worst xi in the memory, then replace xi by x'.
- Repeat from step 2 until a maximum number of iterations has been performed.
The parameters of the search are
- k, the size of the memory. A typical value is in the order of 4 to 10.
- phmcr, the rate of choosing from memory. A typical value is 0. 95.
- ppar, the 'pitch adjustment rate'. Typical values range from 0. 3 to 0. 99.
- bw, the 'distance bandwidth', the amount of change for pitch adjustments.
It is possible to vary the parameters as the search progresses, this gives an effect similar to simulated annealing. Simulated annealing (SA is a generic probabilistic Meta-algorithm for the Global optimization problem namely locating a good approximation to the
In improved harmony search, ppar is increased linearly, while bw is decreased exponentially.
Harmony search applications
The HS algorithm had been successful in a wide variety of optimization problems in the following fields.
Bench-mark problems
- Bench-mark functions
- Traveling salesman problem
- Tour routing
- Music composition
- Sudoku puzzle solving
Real-world problems
- Structural design
- Vehicle routing
- Hydrologic parameter calibration
- Water distribution network design
- Multiple dam scheduling
- Aquifer parameters and zone structures
- Combined heat and power economic dispatch
- Offshore structure mooring
- QoS based multicast routing
- Satellite heat pipe design
Harmony search features
HS has several advantages when compared with traditional gradient-based mathematical optimization techniques as follows:
- HS does not require complex calculus, thus it is free from divergence.
- HS does not require initial value settings for the decision variables, thus it may escape local optima.
- HS can handle discrete variables as well as continuous variables, while gradient-based techniques handle continuous variables only.
Also, the HS algorithm could overcome the drawback of genetic algorithm's building block theory by considering the relationship among decision variables using its ensemble operation. A genetic algorithm (GA is a Search technique used in Computing to find exact or Approximate solutions to optimization and Search
Other Related Algorithms
References
General Information
- Book: Bhanu Prasad, Soft Computing Applications in Industry, 2008. A genetic algorithm (GA is a Search technique used in Computing to find exact or Approximate solutions to optimization and Search Simulated annealing (SA is a generic probabilistic Meta-algorithm for the Global optimization problem namely locating a good approximation to the Tabu search is a mathematical optimization method belonging to the class of local search techniques The ant colony optimization Algorithm (ACO introduced by Marco Dorigo in 1992 in his PhD thesis is a probabilistic technique for solving computational
Theory of Harmony Search
- Particle-Swarm Harmony Search: Omran, M. G. H. and Mahdavi, M. Global-Best Harmony Search, Applied Mathematics and Computation, In Press.
Applications in Artificial Intelligence
Applications in Engineering
- Soil Stability Analysis: Cheng, Y. M. , Li, L. , Lansivaara, T. , Chi, S. C. and Sun, Y. J. An Improved Harmony Search Minimization Algorithm Using Different Slip Surface Generation Methods for Slope Stability Analysis, Engineering Optimization, 2008.
- Offshore Structure Mooring: Ryu, S. , Duggal, A. S. , Heyl, C. N. , and Geem, Z. W. Mooring Cost Optimization via Harmony Search, Proceedings of the 26th International Conference on Offshore Mechanics and Arctic Engineering (OMAE 2007), ASME, San Diego, CA, USA, June 10-15 2007.
- Satellite Heat Pipe Design: Geem, Z. W. and Hwangbo, H. Application of Harmony Search to Multi-Objective Optimization for Satellite Heat Pipe Design, Proceedings of US-Korea Conference on Science, Technology, & Entrepreneurship (UKC 2006), CD-ROM, Teaneck, NJ, USA, Aug. 10-13 2006.
- Ecological Conservation: Geem, Z. W. and Williams, J. C. Ecological Optimization Using Harmony Search, Proceedings of American Conference on Applied Mathematics, Harvard University, Cambridge, MA, USA, March 24-26, 2008.
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