Answers.Body: <p>I couldn't understand your question clearly, however, it think you are making a slim mistake. let's look at the flowing code from &quot;Russell &quot; and do pruning step by step:
  <a href="https://i.sstatic.net/Fwvhe.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Fwvhe.png" alt="enter image description here" /></a>
  <a href="https://i.sstatic.net/TcWDQ.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/TcWDQ.png" alt="enter image description here" /></a>
  <br/>Assume your are In D and you have traversed its both children, Alpha at D becomes 20. We then return back to B, Beta becomes 20 (note that Alpha is -Inf in D). We go to E then L and then back to E. 30 is greater than Beta, so the rest is pruned. Not that Alpha remains -Inf in E, though its value here isn't important. we go back to B the value of Beta remains on changed 20. If we go to F and return back to B Beta remains unchanged and is still 20 (Note that Alpha is still -Inf). We return to A, Alpha becomes 20, And Beta remains +Inf. <br/>
  So, Considering the code, the max node does not get the Alpha value from its children, rather it decides on its own by setting Alpha = max(Alpha, and returned value of its child) after visiting each child. the same is true for Beta.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-01-06T14:47:11.290Z
Answers.LastActivityDate: 2021-01-06T14:57:25.950Z
Answers.LastEditDate: 2021-01-06T14:57:25.950Z
Answers.UserDisplayName: Reza_va
Body: <p>I want to do alpha-beta pruning on this tree:</p>
  <ol>
  <li><p>Consider nodes J and K. K is the max. Therefore, node D has an alpha value of 20, node B has a beta value of 20.</p>
  </li>
  <li><p>Move to Node E. Pass the beta value of 20 to node E. Node L has an alpha value of 30, therefore, at this point 30 (alpha) &gt; 20 (beta) and we can prune the E to M branch.</p>
  </li>
  <li><p>Now is my question. My original beta value at node B was 20, and the alpha value passed up to node A was 20. Then, in step 2, I changed the alpha value to be 30. Do i then change the beta value at node B to be 30, and the alpha value at node A to be 30? (and therefore pass 30 as the alpha value to node C)? Or do I keep the original value of 20 at node B, A and C?</p>
  </li>
  </ol>
  <p><a href="https://i.sstatic.net/XpHg5.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/XpHg5.png" alt="enter image description here" /></a></p>
  
Tags: <minimax><alpha-beta-pruning>
Title: Does the alpha/beta value of parent nodes change if the alpha beta value of the child node changes?
UserDisplayName: Slowat_Kela
ThreadText: # Does the alpha/beta value of parent nodes change if the alpha beta value of the child node changes?
  
  (Asked by: username_0 on 2020-12-31)
  
  I want to do alpha-beta pruning on this tree:
  
  1. Consider nodes J and K. K is the max. Therefore, node D has an alpha value of 20, node B has a beta value of 20.
  2. Move to Node E. Pass the beta value of 20 to node E. Node L has an alpha value of 30, therefore, at this point 30 (alpha) > 20 (beta) and we can prune the E to M branch.
  3. Now is my question. My original beta value at node B was 20, and the alpha value passed up to node A was 20. Then, in step 2, I changed the alpha value to be 30. Do i then change the beta value at node B to be 30, and the alpha value at node A to be 30? (and therefore pass 30 as the alpha value to node C)? Or do I keep the original value of 20 at node B, A and C?
  
  [![enter image description here](https://i.sstatic.net/XpHg5.png)](https://i.sstatic.net/XpHg5.png)
  
  **Tags:** minimax, alpha-beta-pruning
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2021-01-06. Score: 1
  
  I couldn't understand your question clearly, however, it think you are making a slim mistake. let's look at the flowing code from "Russell " and do pruning step by step:
  [![enter image description here](https://i.sstatic.net/Fwvhe.png)](https://i.sstatic.net/Fwvhe.png)
  [![enter image description here](https://i.sstatic.net/TcWDQ.png)](https://i.sstatic.net/TcWDQ.png)
    
  Assume your are In D and you have traversed its both children, Alpha at D becomes 20. We then return back to B, Beta becomes 20 (note that Alpha is -Inf in D). We go to E then L and then back to E. 30 is greater than Beta, so the rest is pruned. Not that Alpha remains -Inf in E, though its value here isn't important. we go back to B the value of Beta remains on changed 20. If we go to F and return back to B Beta remains unchanged and is still 20 (Note that Alpha is still -Inf). We return to A, Alpha becomes 20, And Beta remains +Inf.   
  So, Considering the code, the max node does not get the Alpha value from its children, rather it decides on its own by setting Alpha = max(Alpha, and returned value of its child) after visiting each child. the same is true for Beta.
  
  
  ---
  
  