Principal variation search

Principal Variation Search (PVS) is an algorithm used in game-tree search, particularly in the context of two-player games like chess. It is a refinement of the minimax algorithm, particularly in how it explores the game tree to optimize performance. ### Key Concepts: 1. **Minimax Algorithm**: PVS builds on the classic minimax approach, which aims to minimize the possible loss in a worst-case scenario, maximizing the player's minimum gain.