Answers.Body: <p>With only one line of analysis open, engines are able to prune the other sub-par lines (since you don't want to know anything about them). By leaving multiple lines of analysis open, the engine must fully evaluate each of them, and can't prune any of them (even if they're guaranteed to be worse than the best line showed at the #1 spot).</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-08-20T00:30:30.740Z
Answers.LastActivityDate: 2018-08-20T00:30:30.740Z
Answers.UserDisplayName: Inertial Ignorance
Answers.Body: <p>That's normal, commonly known as multiPV analysis.</p>
  
  <p>Without getting into too much technical details, analysing N number of principal variations require running the engine N times, one for each PV. We need to do that so we can estimate a precise score for each PV.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-06-08T01:38:53.850Z
Answers.Text: Just realized I never accepted an answer for this.
Answers.UserDisplayName: Inertial Ignorance
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-08-20T04:50:50.960Z
Answers.LastActivityDate: 2018-08-20T04:50:50.960Z
Answers.UserDisplayName: SmallChess
Body: <p>When I load up an engine (like Stockfish), it reaches a higher depth quicker if I only leave one line of analysis open. If I leave multiple lines open, it runs slower. Why is this?</p>
  
Tags: <engines><analysis><calculation>
Title: Why do engines run faster if you only have one line of analysis open?
ThreadText: # Why do engines run faster if you only have one line of analysis open?
  
  (Asked by: username_0 on 2018-08-20)
  
  When I load up an engine (like Stockfish), it reaches a higher depth quicker if I only leave one line of analysis open. If I leave multiple lines open, it runs slower. Why is this?
  
  **Tags:** engines, analysis, calculation
  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_1 on 2018-08-20. Score: 4 | Accepted answer
  
  That's normal, commonly known as multiPV analysis.
  
  Without getting into too much technical details, analysing N number of principal variations require running the engine N times, one for each PV. We need to do that so we can estimate a precise score for each PV.
  
  > **Comments:**
  > **username_0**: Just realized I never accepted an answer for this.  
  
  ---
  
  ### Answer by username_0 on 2018-08-20. Score: 3
  
  With only one line of analysis open, engines are able to prune the other sub-par lines (since you don't want to know anything about them). By leaving multiple lines of analysis open, the engine must fully evaluate each of them, and can't prune any of them (even if they're guaranteed to be worse than the best line showed at the #1 spot).
  
  
  ---
  
  