Improved Lower Limits for Pheromone Trails in Ant Colony Optimization

Ant Colony Optimization algorithms were inspired by the foraging behavior of ants that accumulate pheromone trails on the short( It paths to food. Some ACO algorithms employ pheromone trail limits to improve exploration and avoid stagnation by ensuring a non-zero probability of selection for all trails. The MAX-MIN Ant System (MMAS) sets explicit Pheromone trail limits while, the Ant, Colony System (ACS) has implicit pheromone trail limits. Stagnation still occurs in both algorithms with the recommended pheromone. trail limits as the relative importance of the pheromone trails, increases (alpha > 1). Improved estimates of the lower pheromone trail limit (tau(min)) for both algorithms help avoid stagnation and improve performance for alpha > 1. The improved estimates suggest a general rule tu avoid staguation for stochastic algorithms With explicit, or implicit limits on exponential used in proportional selection.