MCTS Information Set

• Information set
  • Tackle the hidden information problem
• Basic idea
  • A tree node represents several different game states
  • But these game states are identical from a player's view
• Variants
  • SO-ISMCTS
  • SO-ISMCTS + POM
  • MO-ISMCTS
• Problems
  • Each tree node contains several different game states
  • These game states should share the same type of available actions
• Discussion 1
  • Question: Need to define those actions carefully?
    • Actions like 'play the 3rd hand card' might NOT BE GOOD?
      • Since the 3rd hand card is different across those different game states
    • Actions like 'play the card with id ID_xxx' might be better
  • Answer: Not necessary
    • Those different game states are identical from the player's view
    • The 3rd hand card is SURELY the same across these game states
• Discussion 2
  • Question: So we don't need to define those actions carefully?
    • Actions like 'play the 3rd hand card' is good?
    • Actions will be projected on another player's tree
  • Answer: Special treatment for the projected action
    • In ideal, another player knows the:
      1. The card id is being played
      2. The target
      3. The choose one phase
    • But, is this really necessary?
      • If a player goes to toilet during another player's turn
        • Does it harm for the player's playing strength?
      • If not, we can just apply a meta-action to another player's tree
        • It finds the tree node with compatible game state
        • and step on it
    • We have transposition table for each turn.
      • Use that to find the correct tree node, and step on it.