# How Does Alpha Beta Pruning Work?

Alpha beta pruning is a search algorithm that attempts to minimize the number of nodes that are evaluated by the algorithm.

It does this by keeping track of two values, alpha and beta, which represent the best value that can be obtained by either player from the current position. The algorithm then prunes any branches of the search tree which cannot affect the final decision.

In computer science, alpha-beta pruning is a search algorithm that seeks to decrease the number of nodes that are evaluated by the minimax algorithm in its search tree. It is an optimization technique for minimax trees. Alpha-beta pruning is typically used in games such as chess and go, where the number of possible moves is large.

The algorithm works by keeping track of two values, alpha and beta, which represent the minimum and maximum values that can be achieved by any player, respectively.

The algorithm then prunes away any branches of the tree whose maximum value (beta) is less than the minimum value (alpha) that can be achieved by the other player. The alpha-beta pruning algorithm can be implemented in any programming language.

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## Alpha-Beta Pruning Example Solved

We’ve all seen how fast computers can play chess these days. They can even beat the best human players! But how do they do it?

One of the key things that makes computer chess so strong is something called “alpha-beta pruning.” This is a technique for searching through the possible moves in a game, and quickly eliminating the ones that are not promising. Let’s take a look at an example to see how this works.

Say we’re playing a game of tic-tac-toe, and it’s our turn to move. We can see that there are nine possible moves we could make: But which one should we choose?

alpha-beta pruning lets us quickly eliminate some of these possibilities.

First, let’s look at the move in the upper left corner. If we make this move, our opponent can immediately force us into a losing position by playing in the middle:

So we can safely eliminate this move from consideration.

## Alpha-Beta Pruning Calculator

What is alpha-beta pruning? Alpha-beta pruning is a search algorithm that helps minimise the number of nodes that need to be evaluated in a game tree. It does this by “pruning” away branches of the tree that are unlikely to contain the best move for the player, based on the current state of the game.

This can save a lot of time and effort when searching for the best move in large game trees. To understand how alpha-beta pruning works, we need to first understand what “alpha” and “beta” values are.

In any given game state, the alpha value is the highest score that can be achieved by the player whose turn it is, while beta is the lowest score that can be achieved by their opponent.

These values are used to keep track of which moves are likely to be more advantageous for each player as the game progresses.

Say we have a simple game tree like this:

A

/ \ B C / \ \

D E F Player 1 Player 2 If we’re looking at this tree from Player 1’s perspective, then we know that any move leading to node D will result in an Alpha score (since D is Player 1’s highest-scoring node).

Similarly, any move leading to node F will result in a Beta score (since F is Player 2’s highest-scoring node). But what about nodes B and C? How do we know whether these moves are good or bad for Player 1?

## Alpha-Beta Pruning Example Problems

Alpha-Beta pruning is a search algorithm that helps speed up the process of finding the best move in a game by discarding certain branches of the search tree. The algorithm works by keeping track of two values, alpha and beta, which represent the best possible move for each player.

When the algorithm reaches a point where it knows that one player can’t improve their position, it prunes away that part of the tree and moves on to another branch.

There are two main types of games where alpha-beta pruning can be used: perfect information games and imperfect information games. In perfect information games, both players have all of the information about the game state at all times. Examples of perfect information games include chess and tic-tac-toe.

On the other hand, in imperfect information games, some information is hidden from one or more players. An example of an imperfect information game is poker. Alpha-beta pruning can be used in any kind of turn-based game where there are Two players with alternating turns That Make Decisions Based on Some kind of Game State .

However, The most common use cases are boardgames such as chess or Go , as well as cardgames such as Poker .

## What is Alpha-Beta Pruning ?

In computer science, alpha-beta pruning is a search algorithm that seeks to decrease the number of nodes that are evaluated by the minimax algorithm in its search tree. It is an optimization technique for minimax trees. The idea of alpha-beta pruning is to identify branches of the game tree that can be cut off without affecting the final outcome of the game.

The algorithm does this by keeping track of two values, alpha and beta, which represent the best move that the maximizer (player 1) can guarantee at any given point, and the best move that the minimizer (player 2) can guarantee at any given point, respectively.

If at any point it is determined that player 1 cannot improve their position beyond what has already been achieved by player 2, then there is no need to evaluate further moves from player 1’s perspective, as player 2 will always win.

Similarly, if it is determined that player 2 cannot improve their position beyond what has already been achieved by player 1, then there is no need to evaluate further moves from player 2’s perspective, as player 1 will always win. In either case, we say that the branch has been “pruned.”

The alpha-beta pruning algorithm works like this:

1. Start with alpha = -∞ and beta = +∞ (representing worst possible outcomes for each player)

2. If it’s Player 1’s turn:

a. Look at each child node

b. Evaluate each child node with a miniMax function call

c. Update alpha to be max(alpha, value returned from miniMax) // want to maximize Player 1’s score so take max() here instead of min() like in regular miniMax

d. If beta ≤ alpha: break // stop evaluating children if Player 2 can force a better result than Player 1 just found

e. Return α // return best option for Player 1

3. Else (it must be Player 2’s turn):

f. Look at each child node

g.. Evaluate each child node with a miniMax function call

h.. Update ββββ := min(ββββ,, value returned fromminiMax)

i.. If β≤α : break

## Alpha-Beta Pruning Online

Alpha-beta pruning is a search algorithm that helps to reduce the number of possible moves that need to be evaluated by the computer in a game of chess, for example.

By discarding certain paths as not promising, it can focus on more promising areas of the search tree. This can save considerable time, as there are often many move sequences that can be quickly eliminated as bad choices.

Credit: ai.stackexchange.com

## What is Alpha-Beta Pruning in Ai With Example?

Alpha-beta pruning is a search algorithm that seeks to minimize the number of nodes that are evaluated by the minimax algorithm in game trees. It is an optimization technique for minimax algorithms. Minimax is a decision-making algorithm used in two player turn-based games such as chess and checkers.

The idea behind alpha-beta pruning is to eliminate branches of the game tree that cannot possibly affect the final outcome, thus reducing the amount of work that needs to be done. The algorithm maintains two values, alpha and beta, which represent the minimum and maximum scores that can be achieved respectively. These values are updated as the search progresses.

If at any point it is determined that achieving a score higher than or equal to beta is impossible, then all remaining branches are discarded since they could not possibly change the outcome of the search (i.e., they would never be reached if optimal play was followed).

Similarly, if it can be shown that a score lower than or equal to alpha is inevitable, then all remaining branches are also discarded since again they could not affect the final result.

## Why Do We Use Alpha-Beta Pruning?

In game theory, alpha-beta pruning is a search algorithm that seeks to decrease the number of nodes that are evaluated by the minimax algorithm in its search tree. It is an optimization of the minimax algorithm that reduces its computational complexity from exponential to polynomial. The idea behind alpha-beta pruning is simple: at each node in the tree, the algorithm keeps track of two values, called the alpha and beta values.

Thealpha value represents the highest score that can be achieved by MAX, while beta represents the lowest score that can be achieved by MIN. If at any point during the search it is determined that MAX cannot achieve a higher score than what has already been found (i.e. if beta <= alpha), then there is no need to explore any further down this branch of the tree since we already know what the result will be. This allows us to prune away large portions of the tree, which drastically reduces both time and space complexity.

Alpha-beta pruning is not without its drawbacks however; in some cases it can lead to suboptimal results if used improperly. Furthermore, it only provides a polynomial speedup over brute force search methods like minimax; for very large trees it can still be quite slow. Nonetheless, it remains a powerful tool in game AI and continues to see widespread use today.

## How Do You Implement Alpha-Beta Pruning?

Alpha-beta pruning is a technique used in game trees to improve the efficiency of the search. It works by eliminating nodes from the tree that can’t possibly affect the final outcome, thereby reducing the amount of work that needs to be done. The simplest way to implement alpha-beta pruning is to use it in conjunction with depth-first search.

When you reach a node, you first check if it’s been visited before. If not, you generate its children and add them to a list of nodes to visit. You then sort this list so that the nodes with the highest potential are visited first.

Once you’ve generated all of a node’s children, you evaluate each one using some heuristic function. The heuristic should take into account things like how close the current position is to winning, how many pieces are on the board, etc. Based on these values, you can assign a score to each child node.

Now comes the important part: when considering which child node to visit next, you compare its score to those of its siblings.

If there’s no chance that visiting this particular child could lead to a better outcome than what has already been found elsewhere in the tree (i.e., if its score is lower than all of its siblings), then there’s no point in visiting it and we can simply prune it from the tree. This is what’s known as alpha-beta pruning.

Of course, sometimes it’s not immediately obvious whether or not visiting a certain node will be beneficial; in these cases, we need to do some more exploration before we can make a decision about whether or not to prune it.

However, even just doing a cursory check like this can often lead to large gains in efficiency without sacrificing too much accuracy.

## Does Order Matter in Alpha-Beta Pruning?

Yes, the order in which moves are searched matters in alpha-beta pruning. If we search the moves in increasing order of their value, then we can cut off searching earlier because all the remaining moves will have lower values.

However, if we search the moves in decreasing order of value, then we might miss out on some good move options because we would have already cut off search for those options.

## Conclusion

Alpha Beta Pruning is a search algorithm used in game theory to find the optimal move in a two-player game. The algorithm is used by both players and takes into account all possible moves by both sides, as well as the consequences of those moves. The AlphaBetaPruning algorithm starts with an initial alpha and beta value.

The player then looks at all possible moves and their corresponding values (alpha for the maximizing player and beta for the minimizing player). The player then compares these values to the current alpha and beta values. If the value is lower than the current alpha value, it means that this move can be safely ignored because there is a better move available for the maximizing player.

If the value is higher than the current beta value, it means that this move can be safely ignored because there is a better move available for the minimizing player. If neither of these conditions are met, then the move is considered “possible” and added to a list of potential moves.

The algorithm then repeats this process for each possible move until there are no more moves left to consider or one of the players has reached an endgame state.

At that point, the player with the highest score wins.

##### Auton Alle
Welcome to Sawsmachine! I'm Auton Alle and I love to talk, teach and encourage creativity through Chainsaws, Lawn mowers, Leaf Blowers, and Pressure Washers.