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Subject: Re: null move question(Fruit)

Author: Volker Böhm

Date: 02:17:33 07/24/04

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Perhaps the following informations from spike can help.
Spike can be compiled with a "what if" functionality that gives information
about the search tree:

sd 6
whatif //shows all root moves
move Win [Alpha;Beta] Val "Returned Value" Nod "Total Nodes Searched"
d3c4 Win [-26;94] Val 0 Nod 185889
c1a3 Win [0;1] Val 0 Nod 189775 Cutoff move e6e2
b4b5 Win [0;1] Val -19996 Nod 189779 Cutoff move
b4c5 Win [0;1] Val -19996 Nod 189783 Cutoff move
d3h7 Win [0;1] Val -19998 Nod 189785 Cutoff move
a1b1 Win [0;1] Val -19996 Nod 189789 Cutoff move
g3g4 Win [0;1] Val -19996 Nod 189793 Cutoff move
c2c3 Win [0;1] Val -19996 Nod 189797 Cutoff move
a4a5 Win [0;1] Val -19996 Nod 189801 Cutoff move
h3h4 Win [0;1] Val -19996 Nod 189805 Cutoff move
a1a2 Win [0;1] Val -19996 Nod 189809 Cutoff move
a1a3 Win [0;1] Val -1 Nod 192221 Cutoff move c5b4
d3b5 Win [0;1] Val 0 Nod 192382 Cutoff move f2f3
d3a3 Win [0;1] Val 0 Nod 193277 Cutoff move c5b4
d3d2 Win [0;1] Val -1 Nod 195073 Cutoff move e6e2
c1e3 Win [0;1] Val 0 Nod 198557 Cutoff move d4e3
d3d4 Win [0;1] Val -154 Nod 198624 Cutoff move c5
d3c3 Win [0;1] Val -354 Nod 198686 Cutoff move d4
d3f1 Win [0;1] Val -563 Nod 198707 Cutoff move f2
d3f3 Win [0;1] Val -546 Nod 198749 Cutoff move f2
d3f5 Win [0;1] Val -330 Nod 198844 Cutoff move f2
d3a6 Win [0;1] Val -41 Nod 198918 Cutoff move e6a
d3e4 Win [0;1] Val -354 Nod 198990 Cutoff move e6
d3g6 Win [0;1] Val -67 Nod 199308 Cutoff move f7g
d3e2 Win [0;1] Val -52 Nod 199348 Cutoff move e6e
d3e3 Win [0;1] Val -163 Nod 199381 Cutoff move d4
c1f4 Win [0;1] Val 0 Nod 214372 Cutoff move e6e2
c2c4 Win [0;1] Val 0 Nod 229743 Cutoff move e6e2
d3d1 Win [0;1] Val 0 Nod 243448 Cutoff move e6e2
d3b3 Win [0;1] Val -6 Nod 244811 Cutoff move f2f1
c1b2 Win [0;1] Val 0 Nod 262409 Cutoff move e6e2
c1d2 Win [0;1] Val 0 Nod 277484 Cutoff move e6e2
c1h6 Win [0;1] Val 0 Nod 301048 Cutoff move e6e2
c1g5 Win [0;1] Val 0 Nod 372784 Cutoff move e6e2

c1b2 is below alpha the "cutoff move" - the answer move that caused a beta
cutoff is e6e2

whatif d3c4 // shows what happens on the d3c4 search line
//   Win [Alpha;Beta] Dep "Search-Depth * 4" Eva "Eval after d3c4" Nod ...
d3c4 Win [-94;26] Dep 19 Eva 625 Nod 173549                 // "Enter d3c4"
 // All answers to d3c4 that has been calculated
 f2f3 Win [-94;26] Val 0 Nod 175275
 f2g3 Win [0;1] Val 0 Nod 176097 Cutoff move b4c5
 c5b4 Win [0;1] Val -58 Nod 176134
 f2f1 Win [0;1] Val -90 Nod 176185 Cutoff move c4f1
 f2c2 Win [0;1] Val -90 Nod 176312 Cutoff move c4c2
 f2h2 Win [0;1] Val -1610 Nod 176338 Cutoff move h1h2
 f2g2 Win [0;1] Val -1610 Nod 176364 Cutoff move h1g2
 f7g6 Win [0;1] Val 0 Nod 176660 Cutoff move c4e6
 f7e8 Win [0;1] Val -725 Nod 176674 Cutoff move c4e6
 f7g8 Win [0;1] Val -30 Nod 176711
 d4d3 Win [0;1] Val -21 Nod 176769
 f7f8 Win [0;1] Val 0 Nod 177085 Cutoff move c4e6
 f2e3 Win [0;1] Val 0 Nod 177120
 f2g1 Win [0;1] Val -1610 Nod 177146 Cutoff move h1g1
 f2e1 Win [0;1] Val 0 Nod 179197 Cutoff move h1g2
 f7e7 Win [0;1] Val -1 Nod 185532 Cutoff move c4c5
 f2f4 Win [0;1] Val 0 Nod 185563
 f2f5 Win [0;1] Val 0 Nod 185594
 g7g6 Win [0;1] Val -24 Nod 185632
 h7h5 Win [0;1] Val -35 Nod 185670
 h7h6 Win [0;1] Val -34 Nod 185708
 f2e2 Win [0;1] Val -15 Nod 185778 Cutoff move c4e2
 f2d2 Win [0;1] Val 0 Nod 185811
 f6f5 Win [0;1] Val -19 Nod 185850
 g7g5 Win [0;1] Val -35 Nod 185889
SetHash:
1. d3c4
d3c4 Win [-26;94] Val 0 Nod 185889

Here what happens on the pv (a little complicated to read):


whatif d3c4 f2f3 h1h2 f3f2 h2h1
Current Hashkey: Index:1601141497 Check:-1507498543
d3c4 Win [-94;26] Dep 19 Eva 625 Nod 173549
No Nullmove because Material + Pawn < Beta
 Check Extension
 f2f3 Win [-26;94] Dep 19 Eva 670 Nod 173550
 No Nullmove because in Check
  h1h2 Win [25;26] Dep 15 Eva 661 Nod 173998
  No Nullmove because Material + Pawn < Beta
   Check Extension
   f3f2 Win [-26;-25] Dep 15 Eva 651 Nod 173999
   No Nullmove because in Check
   One Answer Extension
    h2h1 Win [25;26] Dep 11 Eva 625 Nod 174000
    Cutoff Draw
    h2h1 Win [-26;-25] Val 0 Nod 174000 Fail High
   f3f2 Win [25;26] Val 0 Nod 174000 Cutoff move h2h1
  h1h2 Win [-26;-25] Val 0 Nod 175272 Fail High
  Search Again
  h1h2 Win [-94;26] Dep 15 Eva 661 Nod 175273
  No Nullmove because Hash < Beta
  Chge Win [ -94;0]
   Check Extension
   f3f2 Win [0;94] Dep 15 Eva 651 Nod 175274
   No Nullmove because in Check
   One Answer Extension
    h2h1 Win [-94;0] Dep 11 Eva 625 Nod 175275
    Cutoff Draw
    h2h1 Win [0;94] Val 0 Nod 175275 Cutoff move f3g3
   f3f2 Win [-94;0] Val 0 Nod 175275 Fail High
  h1h2 Win [-26;94] Val 0 Nod 175275
 f2f3 Win [-94;26] Val 0 Nod 175275
SetHash:
1. d3c4
d3c4 Win [-26;94] Val 0 Nod 185889

Conclusion: Spike does not do any nullmoves in this pv because of check
positions and not enough material to do nullmoves. Spike does not try nullmoves
in a position where Material + Pawn < Beta. Fruit does not try nullmoves if Eval
< Beta (as far as I remember). Thus I thin Fruit does not do nullmoves in this
pv too.

Analysis with depth = 8

sd 8
whatif

d3c4 Win [-60;60] Val 0 Nod 944617
c1a3 Win [0;1] Val 0 Nod 961128 Cutoff move e6e2
b4b5 Win [0;1] Val -19996 Nod 961132 Cutoff move e6e1
b4c5 Win [0;1] Val -19996 Nod 961136 Cutoff move e6e1
d3h7 Win [0;1] Val -19998 Nod 961138 Cutoff move e6e1
a1b1 Win [0;1] Val -19996 Nod 961142 Cutoff move e6e1
g3g4 Win [0;1] Val -19996 Nod 961146 Cutoff move e6e1
c2c3 Win [0;1] Val -19996 Nod 961150 Cutoff move e6e1
a4a5 Win [0;1] Val -19996 Nod 961154 Cutoff move e6e1
h3h4 Win [0;1] Val -19996 Nod 961158 Cutoff move e6e1
a1a2 Win [0;1] Val -19996 Nod 961162 Cutoff move e6e1
d3b5 Win [0;1] Val 0 Nod 961914 Cutoff move f2f3
d3a3 Win [0;1] Val 0 Nod 966492 Cutoff move c5b4
d3d2 Win [0;1] Val 0 Nod 982133 Cutoff move e6e2
d3d4 Win [0;1] Val -210 Nod 982673 Cutoff move c5d4
d3c3 Win [0;1] Val -28 Nod 983434 Cutoff move d4c3
d3f1 Win [0;1] Val -57 Nod 983438 Cutoff move f2f1
d3f3 Win [0;1] Val -57 Nod 983444 Cutoff move f2f3
d3f5 Win [0;1] Val -1 Nod 984368 Cutoff move f2f5
d3a6 Win [0;1] Val -58 Nod 984963 Cutoff move e6a6
d3e4 Win [0;1] Val -28 Nod 985277 Cutoff move e6e4
d3g6 Win [0;1] Val -38 Nod 985560 Cutoff move f7g6
d3e2 Win [0;1] Val -52 Nod 985877 Cutoff move e6e2
d3e3 Win [0;1] Val -7 Nod 986313 Cutoff move d4e3
d3b3 Win [0;1] Val 0 Nod 992396 Cutoff move f2f1
a1a3 Win [0;1] Val 0 Nod 1001509 Cutoff move c5b4
c1e3 Win [0;1] Val 0 Nod 1025030 Cutoff move d4e3
d3d1 Win [0;1] Val 0 Nod 1128086 Cutoff move e6e2
c1b2 Win [0;1] Val 0 Nod 1260883 Cutoff move e6e2
c2c4 Win [0;1] Val 0 Nod 1329641 Cutoff move e6e2
c1f4 Win [0;1] Val 0 Nod 1392255 Cutoff move e6e2
c1h6 Win [0;1] Val 0 Nod 1489064 Cutoff move e6e2
c1d2 Win [0;1] Val 0 Nod 1603673 Cutoff move e6e2
c1g5 Win [0;1] Val 0 Nod 1998847 Cutoff move e6e2

what happens if c1b2 e6e2 played ?

whatif c1b2 e6e2
Current Hashkey: Index:1840024820 Check:333744057
c1b2 Win [-1;0] Dep 27 Eva 640 Nod 1128049
No Nullmove because Material + Pawn < Beta
 e6e2 Win [0;1] Dep 23 Eva 558 Nod 1128050
 No Nullmove because Hash(D-3) < Beta   // Hash value shows < Beta -> no
 Nullmove Extension (Hash)              // Hash showes a mate-in-one thread
 No Nullmove because Hash Nullmove Thread // Really no nullmove ;-)
  b4c5 Win [0;1] Val -19996 Nod 1128052 Cutoff move f2g2
  d3h7 Win [0;1] Val -19996 Nod 1128054 Cutoff move f2g2
  d3b3 Win [0;1] Val 0 Nod 1149930 Cutoff move f7g6
  b2d4 Win [0;1] Val -19996 Nod 1149932 Cutoff move f2h2
  d3e2 Win [0;1] Val 0 Nod 1150446 Cutoff move f2e2
  d3d4 Win [0;1] Val -9 Nod 1150798 Cutoff move c5d4
  d3c4 Win [0;1] Val 0 Nod 1169610 Cutoff move f7g6
  a1e1 Win [0;1] Val -14 Nod 1169640 Cutoff move e2e1
  a1f1 Win [0;1] Val -19996 Nod 1169642 Cutoff move f2f1
  a1c1 Win [0;1] Val -19996 Nod 1169644 Cutoff move f2g2
  a1d1 Win [0;1] Val -19996 Nod 1169646 Cutoff move f2g2
  a1b1 Win [0;1] Val -19996 Nod 1169648 Cutoff move f2g2
  b2c3 Win [0;1] Val 0 Nod 1199785 Cutoff move d4c3
  b2a3 Win [0;1] Val -19996 Nod 1199787 Cutoff move f2h2
  b2c1 Win [0;1] Val -19996 Nod 1199788 Cutoff move f2h2
  a1a2 Win [0;1] Val -19996 Nod 1199790 Cutoff move f2h2
  a1a3 Win [0;1] Val -19996 Nod 1199792 Cutoff move f2g2
  c2c4 Win [0;1] Val 0 Nod 1203938 Cutoff move e2b2
  b4b5 Win [0;1] Val -19996 Nod 1203940 Cutoff move f2g2
  c2c3 Win [0;1] Val 0 Nod 1232544 Cutoff move e2b2
  h3h4 Win [0;1] Val -19996 Nod 1232546 Cutoff move f2g2
  g3g4 Win [0;1] Val -19996 Nod 1232548 Cutoff move f2g2
  a1g1 Win [0;1] Val 0 Nod 1250207 Cutoff move e2c2
  d3e4 Win [0;1] Val -38 Nod 1250559 Cutoff move e2e4
  d3f5 Win [0;1] Val -9 Nod 1250957 Cutoff move f2f5
  d3g6 Win [0;1] Val -38 Nod 1251325 Cutoff move f7g6
  a4a5 Win [0;1] Val -19996 Nod 1251327 Cutoff move f2g2
  d3b5 Win [0;1] Val -19996 Nod 1251329 Cutoff move f2h2
  d3a6 Win [0;1] Val -19996 Nod 1251331 Cutoff move f2h2
  d3d2 Win [0;1] Val -9 Nod 1251332 Cutoff move f2h2
  d3d1 Win [0;1] Val 0 Nod 1251333 Cutoff move f2h2
  d3e3 Win [0;1] Val -133 Nod 1251770 Cutoff move d4e3
  d3f3 Win [0;1] Val -9 Nod 1251823 Cutoff move f2f3
  d3c3 Win [0;1] Val -96 Nod 1252080 Cutoff move d4c3
  d3a3 Win [0;1] Val 0 Nod 1260845 Cutoff move e2c2
 SetHash:
 1. c1b2 e6e2
 e6e2 Win [-1;0] Val 0 Nod 1260845 Fail High
c1b2 Win [0;1] Val 0 Nod 1260845 Cutoff move e6e2

Hope that helps.

Greetings Volker



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