Answers.Body: <p>I'm not an expert on this, but my understanding is that every now and then as Stockfish searches there will be a so-called &quot;<a href="https://www.chessprogramming.org/Fail-High" rel="nofollow noreferrer">fail high</a>&quot; or &quot;<a href="https://www.chessprogramming.org/Fail-Low" rel="nofollow noreferrer">fail low</a>&quot; which forces a re-search. Under these situations Stockfish might not know what the best PV is, but it does know the best move it has found is. That is when it outputs a 1-move PV.</p>
  <p>See also <a href="https://www.chessprogramming.org/Aspiration_Windows" rel="nofollow noreferrer">aspiration windows</a> on the Chessprogramming Wiki.</p>
  
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Answers.CreationDate: 2022-12-17T02:53:12.553Z
Answers.LastActivityDate: 2022-12-17T02:53:12.553Z
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Body: <p>Normally the length (sequence of moves) of what stockfish info prints out as 'pv' matches the search depth, but sometimes it doesn't. When determines its length?</p>
  
Tags: <stockfish>
Title: What determines length of stockfish 'pv'?
ThreadText: # What determines length of stockfish 'pv'?
  
  (Asked by: username_0 on 2022-12-16)
  
  Normally the length (sequence of moves) of what stockfish info prints out as 'pv' matches the search depth, but sometimes it doesn't. When determines its length?
  
  **Tags:** stockfish
  
  
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  ## 1 answers
  
  ### Answer by username_1 on 2022-12-17. Score: 1
  
  I'm not an expert on this, but my understanding is that every now and then as Stockfish searches there will be a so-called "[fail high](https://www.chessprogramming.org/Fail-High)" or "[fail low](https://www.chessprogramming.org/Fail-Low)" which forces a re-search. Under these situations Stockfish might not know what the best PV is, but it does know the best move it has found is. That is when it outputs a 1-move PV.
  
  See also [aspiration windows](https://www.chessprogramming.org/Aspiration_Windows) on the Chessprogramming Wiki.
  
  
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