bitbase sharing

[eric_oldre]

The other day I presented a position that gave me problems with my engine, I have found a position that not only gives problems with my engine but also with Latista and tscpegbb that have incorporate the bitbases.

[diag]8/4k3/R7/8/P2KN3/8/8/r7 w - - 1 2[/diag]

FEN: 8/4k3/R7/8/P2KN3/8/8/r7 w - - 1 2

DanaSah v1.8.5:
1 00:00 23 23 0,00 Txa4+ Txa4
2 00:00 316 316 -4,04 Txa4+ Txa4 Re6
3 00:00 1.247 124.700 0,00 Txa4+ Txa4 Re6 Rc4
4 00:00 2.249 112.450 0,00 Txa4+ Txa4 Rg6 Ta7
5 00:00 6.188 206.266 -4,42 Txa4+ Txa4 Rg6 Ta6+ Rf5 Tf6+ Rg4 Cc5
5 00:00 12.960 324.000 -4,41 Ta2 Ta7+ Rg6 Cc5 Td2+ Re5
6 00:00 32.722 467.457 -4,50 Ta2 Cc3 Td2+ Re3 Tc2 Ta7+ Re6 Tc7
7 00:00 81.916 585.114 -4,45 Ta2 Cc3 Td2+ Re3 Tc2 Ta7+ Re6 Tc7 Re5
8 00:00 154.190 700.863 -4,46 Ta2 Cc3 Ta1 Rd5 Txa4 Cxa4 Re7
9 00:00 289.155 781.500 -4,58 Ta2 Cc3 Ta1 Rd5 Tc1 Ta7+ Rg6 Tc7 Tc2
9 00:00 607.406 832.063 -4,52 Ta3 Ta7+ Re6 Cc3 Ta1 Ta6+ Rf5 Ta7 Txa4+ Cxa4
10 00:01 1.063.420 878.859 -4,56 Ta3 Cc3 Re7 Th6 Ta1 Cd5+ Rf7 Cc3 Te1
11 00:03 3.113.218 912.967 -4,62 Ta3 a5 Ta2 Re5 Re8 Cc3 Txa5+ Txa5 Rd7 Cd1 Rc6
11 00:03 3.508.769 913.741 -4,56 Re7 a5 Rd7 Rd5 Rc7 Cc3 Txa5+ Txa5 Rb6 Ta3 Rc7
12 00:04 4.581.690 929.348 -4,62 Re7 a5 Rd7 Rd5 Td1+ Rc5 Tc1+ Rd4 Td1+ Re5 Ta1 Rd5 Td1+ Re5 Rc7
13 00:09 8.622.220 938.217 -4,62 Re7 a5 Rf7 Re5 Ta2 Ta7+ Rg6 Cc3 Ta3 Cb1 Txa5+ Txa5 Rg5 Ta7

In ply 3 and 4, then Rxa4 Rxa4, la eval = 0 ????


Latista:
3 00:00 12.431 177.585 -0,01 Txa4+ Txa4
4 00:00 12.467 178.100 -0,01 Txa4+ Txa4
5 00:00 13.189 164.862 -18,87 Txa4+ Txa4 Re6 Ta5 Rd7
5 00:00 19.372 161.433 -4,83 Ta3 Cd6+ Rf8 Ta8+ Re7 Ce4
5 00:00 22.386 149.240 -4,74 Ta2 Ta7+ Rg6 Ta6+ Rf7 Rd3
6 00:00 36.283 157.752 -4,86 Ta2 Re5 Tc2 Ta7+ Rg6 a5
6 00:00 63.312 166.610 -4,83 Td1+ Re5 Td8 Ta7+ Rg6 a5 Tf8
7 00:00 108.626 175.203 -4,80 Td1+ Re3 Tb1 a5 Te1+ Rd4 Td1+ Re3 Td8
8 00:01 280.141 185.523 -4,83 Td1+ Re3 Te1+ Rf4 Th1 a5 Th4+ Re3 Th3+ Rd4 Th2
9 00:05 1.053.874 185.868 -4,86 Td1+ Re5 Td7 Cg5+ Rg7 a5 Td2 Ta7+ Rg6 Ce4

In ply 3 and ply 4, them Rxa4 Rxa4, eval = 0 ?????

Tscpegbb:
1 00:00 17 17 -3,40 Txa4+
2 00:00 95 95 -4,04 Txa4+ Txa4 Re6
3 00:00 480 480 0,00 Txa4+ Txa4 Re6 Ta6+
4 00:00 3.401 3.401 -4,26 Txa4+ Txa4 Re6 Ta5 Rd7
5 00:00 25.091 313.637 -4,52 Txa4+ Txa4 Re6 Cc3 Rf5 Ca2
6 00:00 173.232 541.350 -4,52 Txa4+ Txa4 Re6 Cc3 Rf5 Ta5+ Rf4 Ca4
7 00:02 1.560.034 636.748 -4,58 Re8 Cc5 Rf7 Tc6 Txa4+ Cxa4 Re7 Cb2

In ply 3 then Rxa4 Rxa4 eval = 0 ?????

Pedro,
I think you are on to something here. First, I assume in the FEN you printed above, you meant for it to be black's move, not whites. Since all the engines are movings black's pieces. Anyway...


After the moves Rxa4+ Rxa4, Ke6, Nd6, we arrive in the following position: (with black to move)

[diag]8/8/3Nk3/8/R2K4/8/8/8 b - - 0 3 [/diag]

At this point Latista is calling the EGBB Library with the following parameters.

int testprobe = probe_egbb(1,27,44,5,43,3,24);

1=blacks turn
27=wking @ d4
44= bking @ e6
5,43=wknight @ d6
3,24 = wrook @ a4

probe_egbb here returns a value = 0 (draw). which is obviously wrong.

maybe I am calling the Dll incorrectly, but the results of the other engines seem to indicate they are doing the same thing. I'll email daniel and alert him to the issue.

EDITED:
well i think i just found the problem. KRNK is not included in the bitbases as far as I can tell. But I'm not aware that there is a way for the bitbase library to say which endgames it can provide "answers" to.

[H.G.Muller]

Interesting that in Spanish the Bishop still has the Arabic name from Shatranj, although there the Alfil (=Elephant) was not really a Bishop but could only jump 2 squares diagonally. In English the Rook kept its Arabic name (which in Persian means Chariot, but which the Italians mistook for Rocca = Fortress...).

Anyway, I still think your diagram has the black King in the wrong place, but that of course does not explain the TB error.

[Daniel Shawul]

Eric, you are right KRNK is not included.
The probe should have returned _NOTFOUND value, i guess it
failed to do this. I wonder if scorpio also makes the same mistake? I will check the problem later. The next release will include all the 4 piece files so that it is possible to cutoff at interior nodes also.
thanks
daniel

[Daniel Shawul]

Problem is fixed now. I tested it with latista and gfruit.
Update of the dll is found here
http://www.geocities.com/dshawul/egbbdll.zip

[Uri Blass]

R = King? But in some of the variations it jumps from d7 to g6! R = Centaur?

Anyway, it seems your bitbase contains errors. Better read it out directly with some bitbase browser for the position after the rook captures a7, than to try to deduce the contenst from how programs that consult it play...

I think that there is a mistake in the diagram and the black king's square is f7(otherwise I cannot understand how the king jumps to g6).

in the diagram the king's square is e7 and I did not see jumps from d7 to g6.

Uri

[Sven Schüle]

Funny thread

Wrong diagram?! (square of black King)
Wrong FEN?! (white or black to move?)
Incomplete bitbases?! (missing KRNK)
Wrong analysis by engines?! But starting from which position now?

Can someone tell me any detail that's correct here

2+2=4
Is that still true?



Sven

[Pedro Castro]

Uri is in the correct thing, the king's position could not be that according to the analysis. Eric was also in the correct thing, the side is dark.

[diag]8/4k3/R7/8/P2KN3/8/8/r7 b - - 0 2[/diag]

Correct FEN is:

FEN: 8/4k3/R7/8/P2KN3/8/8/r7 b - - 0 2

Analysis of the engine in Spanish

DanaSah v1.8.3:
1 00:00 16 16 0,00 Txa4+ Txa4
2 00:00 531 531 -4,04 Txa4+ Txa4 Re6
3 00:00 1.403 1.403 0,00 Txa4+ Txa4 Re6 Ta6+ Rf5
4 00:00 5.606 186.866 -4,04 Txa4+ Txa4 Rf7 Ta7+ Re6
5 00:00 9.691 323.033 -4,15 Ta2 Cc5 Te2
6 00:00 55.804 697.550 -4,45 Ta2 Ta7+ Re6 Cc3 Ta1 Ta6+ Rf5
7 00:00 110.001 785.721 -4,48 Ta2 Cc3 Td2+ Re5 Tg2 Ta7+ Rd8
7 00:00 141.887 788.261 -4,44 Rd8 Ta5 Ta2 Td5+ Re7
8 00:00 309.907 911.491 -4,52 Txa4+ Txa4 Re6 Cc3 Rf5 Ta5+ Rf6 Cb1 Re6 Ta7
8 00:00 532.357 950.637 -4,46 Rd7 Cc5+ Rc8 Ta7 Ta2 Rd5 Td2+ Re5 Rd8
9 00:01 1.329.265 999.447 -4,45 Rd7 Cc5+ Rc7 Te6 Ta3 Th6 Ta2
10 00:02 2.777.342 1.024.849 -4,56 Rd7 a5 Rc7 Rd5 Ta2 Ta7+ Rd8 Re6 Txa5 Txa5
11 00:06 7.381.937 1.060.623 -4,50 Rd7 Rd5 Rc7 Tc6+ Rb7 Cc5+ Rb8 Tb6+ Rc8 Tb4 Ta2 Td4

In this position the engine thought, the dark rook captures the pawn and in the ply 3 the evaluation was zero, that which was illogical since the white ones were with rook and knigth and the blacks with the king.

Daniel has already corrected the dll of the bitbases and now he also goes well with danasah.

Analysis now:

FEN: 8/4k3/R7/8/P2KN3/8/8/r7 b - - 0 2

DanaSah v1.8.3:
1 00:00 16 16 -8,60 Txa4+ Txa4
1 00:00 20 20 -4,52 Rf7
1 00:00 30 30 -4,45 Tb1
1 00:00 34 34 -4,43 Tc1
1 00:00 62 62 -4,41 Td1+ Re5
1 00:00 74 74 -4,28 Ta2
2 00:00 210 21.000 -4,41 Td1+ Re5 Rf7
3 00:00 641 64.100 -4,49 Ta2 a5
4 00:00 3.688 184.400 -4,67 Ta2 Ta7+ Rd8 a5 Te2
5 00:00 10.812 360.400 -4,65 Ta2 a5 Th2 Td6
6 00:00 26.179 523.580 -4,73 Rf7 Ta7+ Rg6 a5 Ta4+ Re5 Ta2
7 00:00 54.803 608.922 -4,76 Tc1 Tb6 Tc2 Tb7+ Re6 a5
8 00:00 154.504 735.733 -4,85 Rd8 a5 Rc8 Tc6+ Rb7 Tb6+ Rc7 Tb5
9 00:00 493.068 880.478 -4,90 Rd8 a5 Rc7 Cc3 Rc8 Ta7 Te1
10 00:01 1.186.612 927.040 -4,91 Rd8 Ta7 Rc8 Cc3 Tc1 a5 Rb8 Td7 Tc2
11 00:03 3.866.479 964.209 -4,87 Rd8 Cc3 Rc7 Tf6 Tg1 Cd5+ Rd7 Tf7+ Re6 Te7+ Rf5

Thank you,

[eric_oldre]

Problem is fixed now. I tested it with latista and gfruit.
Update of the dll is found here
http://www.geocities.com/dshawul/egbbdll.zip

Thanks Daniel! That was certainly a very fast bug fix!