Removing "Duplicate" Analysis from Output?

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Jase

24 Oct, 2018 03:53 PM

Hi Stockfish Team,

I was wondering if it is possible to remove "duplicate" lines from multi-pv analysis of a position?

Here is an example of what I am talking about, in a typical Windmill Position:
FEN: r3rn1k/p5R1/3ppB1p/7q/1P1P4/4N3/P4PPP/4R1K1 w - -

with Multi-pV Analysis, here are the Top 7 lines:

  1. Rxa7+ Kg8 8. Rg7+ Kh8 9. Rg5+ ...

7. Rg5+ Kh7 ...

  1. Rg3+ Kh7 8. Rg7+ Kh8 9. Rxa7+ Kg8 10. Rg7+ Kh8 11. Rg5+ ...

  2. Rf7+ Kg8 8. Rg7+ Kh8 9. Rxa7+ Kg8 10. Rg7+ Kh8 11. Rg5+ ...

  3. Rg4+ Kh7 8. Rg7+ Kh8 9. Rxa7+ Kg8 10. Rg7+ Kh8 11. Rg5+ ...

  4. Rc7+ Kg8 8. Rg7+ Kh8 9. Rxa7+ Kg8 10. Rg7+ Kh8 11. Rg5+ ...

  5. Re7+ Kg8 8. Rg7+ Kh8 9. Rxa7+ Kg8 10. Rg7+ Kh8 11. Rg5+ ...

This is just after a few seconds analysis, but Variations beneath the line Are inserting an unnecessary check, and returning to the same position after 8. ... Kh8. Making six of these lines essentially identical which is why they evaluate close to each other. This also makes multi-pv analysis a little futile, because the only different line 7. Rg5+, comes and goes as it is frequently substituted with additional possible discovered rook/bishop checks.

I hope this makes sense.
Thank you Stockfish Team!
-Jase

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