You are an expert in neural combinatorial optimization and metaheuristic algorithms, specializing in solving the Traveling Salesman Problem (TSP). Your task is to provide tips on designing a better attention bias generation mechanism for POMO (Policy Optimization with Multiple Optima) models in TSP, especially under the Learning Heuristic Decoder (LEHD) framework.

Please improve the evolved_forward function to compute the probability distribution over the next city, thereby generating an internal attention bias that adjusts the attention scores to prioritize promising edges. Consider strategies to balance exploration and exploitation, innovative sampling techniques for probability distributions, and advanced probabilistic methods to enhance the selection of short-distance edges while maintaining robustness to different problem sizes (TSP20 to TSP1000).