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Subject: Something wrong with my futility pruning?

Author: Severi Salminen

Date: 13:46:17 12/05/00


Hi!

Check out this position:

[D]rnbqkbnr/ppp2ppp/8/3pp3/3PP3/8/PPP2PPP/RNBQKBNR w

With futility pruning my program does this:


     Time Depth   Score       Nodes PV
       0    1     -0.14         175 Be3
    0.00    2     -0.19        1851 Be3 Be6
    0.11    3     -0.11        7755 Nf3 Bb4+ Bd2 dxe4 Bxb4 exf3 dxe5 Qxd1+ Kxd1
fxg2 Bxg2
    0.33    4     -0.14       22227 Nf3 exd4 Qxd4 Be6
    0.98    5      0.00       67477 dxe5 dxe4 Qd7+ Qxd7
    3.07    6     -0.12      324618 Nf3 Bg4 Be2 Bxf3 Bxf3 Bb4+
   12.41    7      0.00     1515184 Qh5 dxe4 Qxe5+ Qe7 Qxc7 Qxc7
   33.06    8     -0.09     4203195 dxe5 dxe4 Qxd8+ Kxd8 Bc4 Nc6 Bf4 Bb4+

And without:

     Time Depth   Score       Nodes PV
      50    1     -0.14         175 Be3
    0.05    2     -0.19        1851 Be3 Be6
    0.16    3     -0.11        7850 Nf3 Bb4+ Bd2 dxe4 Bxb4 exf3 dxe5 Qxd1+ Kxd1
fxg2 Bxg2
    0.44    4     -0.14       22555 Nf3 exd4 Qxd4 Be6
    1.10    5     -0.09       73064 Nf3 dxe4 Nxe5 Bb4+ c3
    2.85    6     -0.12      306521 Nf3 Bg4 Be2 Bxf3 Bxf3 Bb4+
    9.61    7     -0.07     1212161 dxe5 dxe4 Qxd8+ Kxd8 Bc4 Bb4+ Nd2
   29.33    8     -0.09     3947537 dxe5 dxe4 Qxd8+ Kxd8 Bc4 Nc6 Bf4 Bb4+

Why the h?%l is the one without futility pruning faster and has less nodes? I
use futility margin of 2 pawns.
My futility code is something like: (I prune check now also...)

if(depth==1)
  if(futility_condition(Moves[k].value)<=alpha)
    continue;

the futility_condition() returns the current material balance + the material
gain of the move+ 200.

Any ideas?

BTW. Does my node counts look reasonable? I'm using MVV/LVA ordering in qsearch
+ nullmoves (R=2).

Severi



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