MullOverThings

Useful tips for everyday

What is the condition for pruning in Alpha-Beta pruning?

What is the condition for pruning in Alpha-Beta pruning?

The condition to prune a node is when alpha becomes greater than or equal to beta. Start with assigning the initial values of alpha and beta to root and since alpha is less than beta we don’t prune it. Carry these values of alpha and beta to the child node on the left.

Which nodes will be pruned if you apply Alpha-Beta pruning algorithm?

Working of Alpha-beta Pruning. We will first start with the initial move. We will initially define the alpha and beta values as the worst case i.e. α = -∞ and β= +∞. We will prune the node only when alpha becomes greater than or equal to beta.

Is alpha-beta pruning optimal?

Ideal ordering: The ideal ordering for alpha-beta pruning occurs when lots of pruning happens in the tree, and best moves occur at the left side of the tree. We apply DFS hence it first search left of the tree and go deep twice as minimax algorithm in the same amount of time. Complexity in ideal ordering is O(bm/2).

Why is it called Alpha-Beta pruning?

It is called Alpha-Beta pruning because it passes 2 extra parameters in the minimax function, namely alpha and beta. Let’s define the parameters alpha and beta. Alpha is the best value that the maximizer currently can guarantee at that level or above.

How does alpha beta pruning improve minimax algorithm?

Alpha-Beta pruning is not actually a new algorithm, rather an optimization technique for minimax algorithm. It reduces the computation time by a huge factor. This allows us to search much faster and even go into deeper levels in the game tree.

How to check minimax search with alpha beta?

This is pseudo-code for minimax search with alpha-beta pruning, or simply alpha-beta search. We can verify that it works as intended by checking what it does on the example tree above. Each node is shown with the [ min, max] range that minimax is invoked with. Pruned parts of the tree are marked with X.

What happens when you prune a minimax tree?

When the optimal child is selected at every opportunity, alpha-beta pruning causes all the rest of the children to be pruned away at every other level of the tree; only that one child is explored. This means that on average the tree can searched twice as deeply as before—a huge increase in searching performance.

Why is the minimax algorithm called a game tree?

Minimax is called so because it helps in minimizing the loss when the other player chooses the strategy having the maximum loss. Game Tree: It is a structure in the form of a tree consisting of all the possible moves which allow you to move from a state of the game to the next state.