Answers.Body: <p>50 centipawn difference may mean a lot in some positions and practically nothing in other ones.</p>
  <p>In this particular position though, it's pretty clear that <strong>Re8</strong> is an useful move, as you pointed out, it takes control of <em>e-file</em>. On the other hand it's hard to say what <strong>Qd7</strong> actually accomplishes. True, it connects the rooks - but is this really important in this position? On the other hand it cuts off bishop retreat and queen on <em>d7</em> just feels very awkward, a bit too exposed if you want. <em>d8</em> may even be better square for her than <em>d7</em>.</p>
  <p>Opening principles still matter of course, even if this position has more of middlegame character. Here however, you have a conflict between two principles: connecting the rooks and putting a rook on open file. So the question is which is more important there, which you have to decide both by calculation and by asking yourself, what move actually does, not just which principle it follows.</p>
  
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Answers.Text: Thanks for the explanation. But how do you calculate now ? I mean, you mentioned Qd7 “cuts off bishop retreat ”, indeed, also it cuts off knight retreat  — but in such position , how would you (or any strong players that can feel the difference) calculate till sees the importance of bishop or knight’s retreat to square d7? I’m just wondering , roughly, how deep would that calculation needs, or how many variations would one needs to calculate till “see” it?
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Answers.Text: In this particular case I didn't calculate that bishop retreat is actually needed - and it won't be, at least not for long time. It's just annoying that you don't have it available if you ever need it.
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Body: <p>In the below opening, after 10. O-O-O, the best move for black is 10... Re8, this is understandable, to control the half-open file; however, 10... Qd7 is also following the principle -- to connect the rooks, but unfortunately SmallFish shows this loses about 0.5, or 50 centipawn.</p>
  <p>How could one be able to sense the 50 centipawn? It seems &quot;just follow opening principles&quot; does not work any more to such subtle
  distinction. How could one tell the difference? Is there some deduction, calculation, or methodology would help?</p>
  <pre><code>[FEN &quot;&quot;]
  
  1. b3 e5 2. Bb2 Nc6 3. e3 Nf6 4. Bb5 d6 5. d4 exd4 6. Qxd4 Bd7 7. Bxc6 Bxc6 8. Nf3 Be7 9. Nc3 O-O 10. O-O-O
  </code></pre>
  
Tags: <opening>
Title: How to sense the 0.5 difference
ThreadText: # How to sense the 0.5 difference
  
  (Asked by: username_0 on 2024-03-15)
  
  In the below opening, after 10. O-O-O, the best move for black is 10... Re8, this is understandable, to control the half-open file; however, 10... Qd7 is also following the principle -- to connect the rooks, but unfortunately SmallFish shows this loses about 0.5, or 50 centipawn.
  
  How could one be able to sense the 50 centipawn? It seems "just follow opening principles" does not work any more to such subtle
  distinction. How could one tell the difference? Is there some deduction, calculation, or methodology would help?
  
  ```
  [FEN ""]
  
  1. b3 e5 2. Bb2 Nc6 3. e3 Nf6 4. Bb5 d6 5. d4 exd4 6. Qxd4 Bd7 7. Bxc6 Bxc6 8. Nf3 Be7 9. Nc3 O-O 10. O-O-O
  
  ```
  
  **Tags:** opening
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2024-03-16. Score: 2 | Accepted answer
  
  50 centipawn difference may mean a lot in some positions and practically nothing in other ones.
  
  In this particular position though, it's pretty clear that **Re8** is an useful move, as you pointed out, it takes control of *e-file*. On the other hand it's hard to say what **Qd7** actually accomplishes. True, it connects the rooks - but is this really important in this position? On the other hand it cuts off bishop retreat and queen on *d7* just feels very awkward, a bit too exposed if you want. *d8* may even be better square for her than *d7*.
  
  Opening principles still matter of course, even if this position has more of middlegame character. Here however, you have a conflict between two principles: connecting the rooks and putting a rook on open file. So the question is which is more important there, which you have to decide both by calculation and by asking yourself, what move actually does, not just which principle it follows.
  
  > **Comments:**
  > **username_0**: Thanks for the explanation. But how do you calculate now ? I mean, you mentioned Qd7 “cuts off bishop retreat ”, indeed, also it cuts off knight retreat  — but in such position , how would you (or any strong players that can feel the difference) calculate till sees the importance of bishop or knight’s retreat to square d7? I’m just wondering , roughly, how deep would that calculation needs, or how many variations would one needs to calculate till “see” it?  
  > **username_1**: In this particular case I didn't calculate that bishop retreat is actually needed - and it won't be, at least not for long time. It's just annoying that you don't have it available if you ever need it.  
  
  ---
  
  