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Subject: Re: Mate in 7 moves - diagram

Author: Jeremiah Penery

Date: 22:01:36 09/27/00

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On September 27, 2000 at 04:45:38, Eduard Nemeth wrote:

>[D]8/8/p3R3/1p5p/1P5p/6rp/5K1p/7k w - - 0 1
>
>Shredder 4 and Fritz 6a this don't find !

I have a modified Crafty that solves this well enough:

7->   0.33  -0.04   1. Re1+ Rg1 2. Rf1 Rxf1+ 3. Kxf1 a5
                    4. bxa5 b4 5. a6 b3
8     0.34     --   1. Re1+
8     1.85     ++   1. Re1+!!
8     1.86   0.61   1. Re1+ Rg1 2. Rf1 Rxf1+ 3. Kxf1 a5
                    4. bxa5 b4 5. a6 b3 6. a7 b2 7. a8=Q#
8->   1.88   0.61   1. Re1+ Rg1 2. Rf1 Rxf1+ 3. Kxf1 a5
                    4. bxa5 b4 5. a6 b3 6. a7 b2 7. a8=Q#
9     1.89     --   1. Re1+
9     5.86     ++   1. Re1+!!
9     5.87  Mat07   1. Re1+ Rg1 2. Rf1 Rxf1+ 3. Kxf1 a5
                    4. bxa5 b4 5. a6 b3 6. a7 b2 7. a8=Q#
9->   5.89  Mat07   1. Re1+ Rg1 2. Rf1 Rxf1+ 3. Kxf1 a5
                    4. bxa5 b4 5. a6 b3 6. a7 b2 7. a8=Q#

Part of the modifications I did was to not do a nullmove at all when the total
depth is 5 or less, and it also doesn't use nullmove when depth_remaining is 2
or less.  The normal "adaptive null-move reduction" has also been changed, to
only use r=3 when depth is more than 12 instead of the normal 6.  Here's the
modified parts of the nullmove code from Crafty's search.c

  if (iteration_depth > 5 && depth > 2) {
# if defined(NULL_MOVE_DEPTH)
                  ....
		  null_depth=(depth > 12*INCPLY) ? 2*INCPLY : 3*INCPLY;
                  ....
# endif
  }



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