Finding the Needle in the Haystack: Solving Combinatorial Optimization with Metaheuristics

Sanjeev K
3 min readApr 28, 2023

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Introduction

Optimization problems are a fundamental part of various fields ranging from engineering to finance, and they aim to find the optimal solution to a given problem. However, solving these problems can be challenging, especially when the input variables are discrete. Metaheuristic algorithms are widely used to solve combinatorial optimization problems, and they provide near-optimal solutions in a reasonable amount of time. In this blog post, we will discuss metaheuristic algorithms, their principles, and their classifications. Additionally, we will focus on two commonly used metaheuristic algorithms, simulated annealing, and genetic algorithms, for solving combinatorial optimization problems.

Metaheuristic Algorithms

Metaheuristic algorithms are problem-solving strategies that combine various concepts to guide a subordinate heuristic in exploring and exploiting the search space. These algorithms use learning strategies to structure information, which helps them to efficiently discover near-optimal solutions. Metaheuristics can be considered generalizations of heuristics, which are problem-solving strategies based on intuition or experience.

fig: Metaheuristics classification (credit: Saman M Almufti)

Metaheuristics can be broadly classified into two categories: single solution and population-based algorithms. Single-solution algorithms focus on exploring and intensifying the search space to find a single best solution, whereas population-based algorithms generate a set of solutions and use selection and reproduction techniques to generate new solutions.

Two key principles of metaheuristics are exploration and exploitation. Exploration aims to quickly identify regions in the search space with high-quality solutions, also known as diversification. On the other hand, exploitation aims not to waste too much time in regions of the search space that are either already explored or do not provide high-quality solutions but to focus the search on a local region that is believed to have a current-good solution, also known as intensification.

Simulated Annealing and Genetic Algorithm

Simulated annealing and genetic algorithm are commonly used metaheuristic algorithms for solving combinatorial optimization problems.

Simulated Annealing

Simulated Annealing is a stochastic optimization algorithm that mimics the physical process of annealing in metals. The algorithm starts with an initial solution and gradually improves it by accepting worse solutions with some probability. This probability decreases as the algorithm progresses, and the algorithm converges to a near-optimal solution. Simulated Annealing is particularly useful for problems with a large number of local optima.

Genetic Algorithm

A genetic Algorithm is an optimization algorithm that simulates the natural selection process of living organisms. The algorithm starts with a population of candidate solutions and uses selection and reproduction techniques to generate new solutions. The new solutions are then evaluated based on their fitness, and the process is repeated until a near-optimal solution is found. Genetic Algorithm is particularly useful for problems with multiple objectives.

Conclusion

In conclusion, metaheuristic algorithms are widely used to solve combinatorial optimization problems in various fields. These algorithms combine various concepts to guide a subordinate heuristic in exploring and exploiting the search space. Simulated Annealing and Genetic Algorithm are commonly used metaheuristic algorithms for solving combinatorial optimization problems. The selection of a particular metaheuristic algorithm is challenging, and there is no universally better-performing algorithm. Therefore, it is essential to assess how well an algorithm performs on a few sample problems to determine its effectiveness.

References

  1. https://medium.com/@sanjeev_s/from-darwin-to-data-science-an-introduction-to-genetic-algorithms-c8fd554e441c
  2. Christian Blum and Andrea Roli. Metaheuristics in combinatorial optimization: Overview and conceptual comparison. ACM Computing Surveys, 35(3):268–308, 2003.
  3. Ibrahim H. Osman and Gilbert Laporte. Metaheuristics: A bibliography. Annals of Operations Research, 63(5):511–623, 1996.
  4. Saman M Almufti. Historical survey on metaheuristics algorithms. International Journal of Scientific World, 7(1):1, 2019.

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