Search Extension

• Search-until-quiescent
  • Captures can lead to volatile board positions
  • Extend the search past the depth limit until no captures are possible
• Singular extension
  • If one position is "much better" than any others, it could be deceptive
  • Extend the search past the depth limit for only one position until it becomes "normal"
• Ordering heuristic
  • Use the board evaluation function to look at "good" positions first
  • In principle, might help alpha-beta with pruning
• Position databases
  • Transposition table
    • Fixed-size hash table containing previously evaluated boards
    • Most valuable at shallow depths
  • Endgame database
    • Precompute absolute board values for limited scenarios
    • Effectively extends search depth