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First post (and FailHigh question!)
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Natale Galioto



Joined: 03 Jun 2013
Posts: 286
Location: Italy

PostPost subject: First post (and FailHigh question!)    Posted: Fri Jun 14, 2013 10:02 am Reply to topic Reply with quote

Hello everyone,
my name is Natale and (after a lot of years, again) I decided it was time to try develop a new engine from scratch.

After reading suggestions on this forum and wikis on internet, I actually created the (not so) basic structure:
- PVS
- Q-search
- ID
- IID
- TT
- Killers
- Basic Move Order
- Eval with material only

All the stuff (after fixing A LOT of bugs) seems to work properly, actually tested with mate positions only (as I don't have evaluation at all), but I have a question I cannot find an answer to:

In mate tests it often fails high at root (when can it fail high? it should have seen a mate already, right?), but the research gives back the original score. As an example I post some iteration of this basic KNB-K endgame:
Code:
FEN: 8/8/3K4/8/8/3N4/8/3B3k w - -
--------------------------------------------------------------------------------
     time      depth    move        nps     score        line
--------------------------------------------------------------------------------
...
previous iterations omitted...
...
--------------------------------------------------------------------------------
 00:00:01.431   14     Bd1-c2       7.4M    +6.00        1. Bd1-c2    Kh1-g1
                                                         2. Bc2-b1    Kg1-f1
                                                         3. Bb1-a2    Kf1-g1
                                                         4. Ba2-b3    Kg1-f1
                                                         5. Bb3-d1    Kf1-g1
                                                         6. Bd1-c2    Kg1-f1
                                                         7. Bc2-b1    Kf1-g1
 00:00:01.524   14     Kd6-e5       6.9M    +6.50 >
 00:00:01.720   14     Kd6-e5       7.6M    +6.00        1. Kd6-e5    Kh1-g2
                                                         2. Ke5-f4    Kg2-h2
                                                         3. Kf4-g5    Kh2-g1
                                                         4. Bd1-f3    Kg1-h2
                                                         5. Bf3-e2    Kh2-g1
                                                         6. Be2-d1    Kg1-f1
                                                         7. Bd1-c2    Kf1-g1
...
iterations 15-16-17-18 omitted...
...
--------------------------------------------------------------------------------
 00:02:47.444   19     Kd6-e5       8.8M    +6.50 >
 00:03:24.178   19     Kd6-e5!!     9.5M  +MATE11        1. Kd6-e5    Kh1-h2
                                                         2. Ke5-f4    Kh2-h3
                                                         3. Bd1-e2    Kh3-h4
                                                         4. Nd3-e1    Kh4-h3
                                                         5. Be2-g4+   Kh3-h2
                                                         6. Kf4-f3    Kh2-g1
                                                         7. Bg4-h3    Kg1-h2
                                                         8. Kf3-g4    Kh2-g1
                                                         9. Kg4-g3    Kg1-h1
                                                        10. Bh3-g2+   Kh1-g1
                                                        11. Ne1-f3#

As shown above, at iteration 14 it fails high (search window is 50cp, n=b=300cp) but the score returned back by a research is still 6.00! It keeps failing high at iterations 15-16-17-18 but score is still 6.00 in research, then at ply 19 it finally sees a mate in 11 and report it correctly. Is this a search instability introduced by TT & co.? I tried to disable Killers,Q-search,IID, TT completely or TT-cutoffs only (so I can keep PV), and the problem seems to disappear only when disabling TT stuff (completely or cut-offs only, no difference) as it doesn't fail high anymore (and takes ages to mate...). Tried to debug this thing and it was hard, I saw a TT cut in the research returning the score 6.00. Now I'm not sure if it's a real TT bug or simply "search instability" I have live with... Switching side to move or colors behaves similar to this, except it's failing low (score is -6.00, fail-low with score less than -6.50, but score is back to -6.00 after research).


Best regards,
Natl.
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Display posts from previous:   
Subject Author Date/Time
First post (and FailHigh question!) Natale Galioto Fri Jun 14, 2013 10:02 am
      Re: First post (and FailHigh question!) Chan Rasjid Fri Jun 14, 2013 2:52 pm
            Re: First post (and FailHigh question!) Natale Galioto Fri Jun 14, 2013 4:03 pm
            Re: First post (and FailHigh question!) Natale Galioto Fri Jun 14, 2013 8:32 pm
                  Re: First post (and FailHigh question!) Chan Rasjid Fri Jun 14, 2013 9:29 pm
                        Re: First post (and FailHigh question!) Chan Rasjid Fri Jun 14, 2013 9:42 pm
                        Re: First post (and FailHigh question!) Sven Schüle Fri Jun 14, 2013 10:04 pm
                              Re: First post (and FailHigh question!) H.G.Muller Sat Jun 15, 2013 6:25 am
                                    Re: First post (and FailHigh question!) Thomas Petzke Sat Jun 15, 2013 8:32 am
                                          Re: First post (and FailHigh question!) Natale Galioto Sat Jun 15, 2013 10:57 am
                                                Re: First post (and FailHigh question!) Thomas Petzke Sat Jun 15, 2013 12:18 pm
                                                      Re: First post (and FailHigh question!) Chan Rasjid Sun Jun 16, 2013 9:29 am
                                                            Re: First post (and FailHigh question!) Henk van den Belt Sun Jun 16, 2013 9:41 am
                                    Re: First post (and FailHigh question!) Sven Schüle Sun Jun 16, 2013 8:29 am
                              Re: First post (and FailHigh question!) Natale Galioto Sat Jun 15, 2013 10:52 am
                                    Re: First post (and FailHigh question!) Michael Hoffmann Sat Jun 15, 2013 12:00 pm
                                    Re: First post (and FailHigh question!) Henk van den Belt Sun Jun 16, 2013 9:19 am
                                          Re: First post (and FailHigh question!) Henk van den Belt Sun Jun 16, 2013 4:45 pm
                                    Re: First post (and FailHigh question!) Sven Schüle Sun Jun 16, 2013 6:33 pm
                                          Re: First post (and FailHigh question!) Natale Galioto Sun Jun 16, 2013 11:06 pm
                                                Re: First post (and FailHigh question!) Sven Schüle Mon Jun 17, 2013 6:54 am
                                                      Re: First post (and FailHigh question!) Henk van den Belt Mon Jun 17, 2013 7:11 am
                                                      Re: First post (and FailHigh question!) Chan Rasjid Mon Jun 17, 2013 7:56 am
                                                            Re: First post (and FailHigh question!) Natale Galioto Mon Jun 17, 2013 8:46 am
                                                                  Re: First post (and FailHigh question!) Chan Rasjid Mon Jun 17, 2013 10:54 am
                                                                        Re: First post (and FailHigh question!) Natale Galioto Mon Jun 17, 2013 2:39 pm
                                                                              Re: First post (and FailHigh question!) Sven Schüle Mon Jun 17, 2013 5:16 pm
                                                                              Re: First post (and FailHigh question!) Chan Rasjid Mon Jun 17, 2013 6:13 pm
                                                                                    Re: First post (and FailHigh question!) Sven Schüle Mon Jun 17, 2013 8:51 pm
                                                                                          Re: First post (and FailHigh question!) Natale Galioto Mon Jun 17, 2013 9:56 pm
                                                                                          Re: First post (and FailHigh question!) Ronald de Man Mon Jun 17, 2013 10:16 pm
                                                                                          Re: First post (and FailHigh question!) Natale Galioto Mon Jun 17, 2013 10:38 pm
                                                                                          Re: First post (and FailHigh question!) Ronald de Man Tue Jun 18, 2013 12:06 am
                                                                                          Re: First post (and FailHigh question!) Chan Rasjid Tue Jun 18, 2013 1:37 am
                                                                                          Re: First post (and FailHigh question!) Natale Galioto Tue Jun 18, 2013 9:54 am
                                                                                          Re: First post (and FailHigh question!) Ronald de Man Tue Jun 18, 2013 12:11 pm
                                                                                          Re: First post (and FailHigh question!) Natale Galioto Tue Jun 18, 2013 2:19 pm
                                                                                          Re: First post (and FailHigh question!) Chan Rasjid Tue Jun 18, 2013 4:12 pm
                                                                                          Re: First post (and FailHigh question!) Natale Galioto Tue Jun 18, 2013 7:59 pm
                                                                                          Re: First post (and FailHigh question!) Chan Rasjid Tue Jun 18, 2013 11:45 pm
                                                                                          Re: First post (and FailHigh question!) Natale Galioto Wed Jun 19, 2013 6:57 am
                                                                                          Re: First post (and FailHigh question!) Sven Schüle Wed Jun 19, 2013 12:32 pm
                                                                                          Re: First post (and FailHigh question!) Natale Galioto Wed Jun 19, 2013 11:09 pm
                                                                                          Re: First post (and FailHigh question!) Chan Rasjid Thu Jun 20, 2013 8:09 am
                                                                                          Re: First post (and FailHigh question!) Natale Galioto Thu Jun 20, 2013 9:15 am
                                                                                          Re: First post (and FailHigh question!) Patrice Duhamel Fri Jun 21, 2013 4:57 pm
                                                                                          Re: First post (and FailHigh question!) Chan Rasjid Fri Jun 21, 2013 9:29 pm
                                                                                          Re: First post (and FailHigh question!) Patrice Duhamel Fri Jun 21, 2013 10:16 pm
                                                                                          Re: First post (and FailHigh question!) Chan Rasjid Sat Jun 22, 2013 9:04 am
                                                                                          Re: First post (and FailHigh question!) Sven Schüle Sat Jun 22, 2013 9:48 am
                                                                                          Re: First post (and FailHigh question!) Natale Galioto Wed Jul 10, 2013 5:41 pm
                                                                                          Re: First post (and FailHigh question!) Sven Schüle Wed Jul 10, 2013 11:18 pm
                                                                                          Re: First post (and FailHigh question!) Sven Schüle Wed Jul 10, 2013 11:56 pm
                                                                                          Re: First post (and FailHigh question!) Natale Galioto Thu Jul 11, 2013 12:26 am
                                                                                          Re: First post (and FailHigh question!) Natale Galioto Thu Jul 11, 2013 12:16 am
                                                                                          Re: First post (and FailHigh question!) Sven Schüle Thu Jul 11, 2013 8:59 am
                                                                                          Re: First post (and FailHigh question!) Natale Galioto Thu Jul 11, 2013 9:52 am
                                                                                          Re: First post (and FailHigh question!) Sven Schüle Thu Jul 11, 2013 8:50 pm
                                                                                          Re: First post (and FailHigh question!) Thomas Petzke Thu Jun 20, 2013 12:36 pm
                                                                                          Re: First post (and FailHigh question!) Chan Rasjid Thu Jun 20, 2013 3:40 pm
                                                                                          Re: First post (and FailHigh question!) Thomas Petzke Thu Jun 20, 2013 4:15 pm
                                                                                          Re: First post (and FailHigh question!) Chan Rasjid Thu Jun 20, 2013 6:10 pm
                                                                                          Re: First post (and FailHigh question!) Thomas Petzke Fri Jun 21, 2013 5:57 pm
                                                                                          Re: First post (and FailHigh question!) Ronald de Man Fri Jun 21, 2013 7:40 pm
                                                                                          Re: First post (and FailHigh question!) Thomas Petzke Fri Jun 21, 2013 8:48 pm
                                                                                          Re: First post (and FailHigh question!) Michael Hoffmann Fri Jun 21, 2013 9:08 pm
                                                                                          Re: First post (and FailHigh question!) Chan Rasjid Fri Jun 21, 2013 9:40 pm
                                                                                          Re: First post (and FailHigh question!) Chan Rasjid Thu Jun 20, 2013 4:01 pm
                                                                                          Re: First post (and FailHigh question!) Sven Schüle Thu Jun 20, 2013 4:17 pm
                                                                                          Re: First post (and FailHigh question!) Chan Rasjid Thu Jun 20, 2013 5:10 pm
                                                                                          Re: First post (and FailHigh question!) Sven Schüle Thu Jun 20, 2013 9:11 pm
                                                                                          Re: First post (and FailHigh question!) Chan Rasjid Fri Jun 21, 2013 5:08 am
                                                                                          Re: First post (and FailHigh question!) Sven Schüle Fri Jun 21, 2013 10:07 am
                                                                                          Re: First post (and FailHigh question!) Chan Rasjid Fri Jun 21, 2013 10:32 am
                                                                                          Re: First post (and FailHigh question!) Sven Schüle Fri Jun 21, 2013 11:28 am
                                                                                          Re: First post (and FailHigh question!) Chan Rasjid Fri Jun 21, 2013 3:31 pm
                                                                                          Re: First post (and FailHigh question!) Patrice Duhamel Tue Jun 18, 2013 4:43 pm
                                                                                          Re: First post (and FailHigh question!) Natale Galioto Tue Jun 18, 2013 8:01 pm
                                                                                          Re: First post (and FailHigh question!) Patrice Duhamel Tue Jun 18, 2013 8:50 pm
                                                                                          Re: First post (and FailHigh question!) Natale Galioto Tue Jun 18, 2013 8:59 pm
                                                                                          Re: First post (and FailHigh question!) Patrice Duhamel Tue Jun 18, 2013 9:42 pm
                                                                                          Re: First post (and FailHigh question!) Natale Galioto Tue Jun 18, 2013 9:56 pm
                                                                                          Re: First post (and FailHigh question!) Patrice Duhamel Wed Jun 19, 2013 6:48 am
                                                                                          Re: First post (and FailHigh question!) Natale Galioto Wed Jun 19, 2013 7:03 am
                                                                  Re: First post (and FailHigh question!) Sven Schüle Mon Jun 17, 2013 2:14 pm
                                                                        Re: First post (and FailHigh question!) Natale Galioto Mon Jun 17, 2013 2:59 pm
                  Re: First post (and FailHigh question!) Sven Schüle Fri Jun 14, 2013 9:48 pm
      Further analysis Natale Galioto Sun Jul 28, 2013 9:45 pm
            Re: Further analysis Sven Schüle Mon Jul 29, 2013 11:01 pm
                  Re: Further analysis Natale Galioto Thu Aug 01, 2013 10:31 am
Post new topic    TalkChess.com Forum Index -> Computer Chess Club: Programming and Technical Discussions

 
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