Thor's Hammer

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Thor's Hammer, (Mjoelner) a WinBoard compatible open source chess engine by Toma Roncevic written in C++, first released in December 2002. Mjoelner participated at the 2nd Italian Engine Contest played on-line in 2001/2002, and Thor's Hammer played the CIPS 2003 with 3½/7. Thor's Hammer is available from Jim Ablett's Winboard Chess Projects site, who also reported a huge speed gain of the 64-bit over the 32-bit build, which is quite typical for bitboard engines.

=Description=

Move Generation
Thor's Hammer is a bitboard engine without explicitly scanning bits of set-wise attack intersections, in particular sliding piece attacks. It applies a staged move generation with testing legality of hash- and killer moves. Otherwise, it generates quiet moves of sliding pieces loop-wise for each ray-direction. Even sliding captures are generated quite similar to the blocker loop of a vector attack array representation, but with the important difference that testing the capture condition is done before entering the loop rather than after loop execution. If the intersection of the negative rays from a square with the opponent pieces as capture target is greater than the intersection with own pieces, a capture is possible on that ray. south east (f6)   &  opponent pieces  &  own pieces . . . . . . . .     . . . . . . . .     . . . . . . . .  . . . . . . . .      . . . . . . . .     . . . . . . . .  . . . . . . . .      . . . . . . . .     . . . . . . . .  . . . . 1 . . .      . . . . . . . .     . . . . . . . .  . . . 1 . . . .      . . . 1 . . . .  >  . . . . . . . .  . . 1 . . . . .      . . . . . . . .     . . . . . . . .  . 1 . . . . . .      . . . . . . . .     . 1 . . . . . .  1 . . . . . . .      . . . . . . . .     1 . . . . . . . To apply the same trick for the positive rays, incremental updated reverse bitboards are used : if(ptype[color][i]==BISHOP || ptype[color][i]==QUEEN) { fmask=~omask; if((seFrom[xp]&omask) > (seFrom[xp]&nmask)) { c=xp-7; while((setBit(c) & (fmask))) c-=7; *moves++ = setMove(i,c); }   if((seFrom[63-xp]&orotmask) > (seFrom[63-xp]&nrotmask)) { c=xp+7; while((setBit(c) & (fmask))) c+=7; *moves++ = setMove(i,c); }   if( ...  }  ... On processors with slow bitscan, i.e. Intel's x86 NetBurst microarchitecture, the compact scan loops to skip empty squares inside the instruction pipeline should not that much slower on average.

Search
The search relies on iterative deepening with aspiration windows and PVS, transpostion table, adaptive null move pruning, internal iterative deepening, check-, passed pawn- and recapture extensions.

Evaluation
Evaluation counts material and positionally considers pawn structure utilizing a pawn hash table, passed pawns including rule of the square in the pawn endings, king safety in the middlegame and centralization in the endgame, mobility and multiple other features.

=See also=
 * Freyr

=Forum Posts=
 * Thor's Hammer new version by toma, Winboard Forum, November 15, 2004
 * Thor's Hammer 2.25 by toma, Winboard Forum, February 14, 2005
 * Gauntlet Thor's Hammer v2.25 and GES v1.36 - games by Karl-Heinz Söntges, CCC, March 30, 2005
 * Gauntlets Liste B 5' + 5" Thor's Hammer v2.28 - games by Karl-Heinz Söntges, CCC, August 01, 2005
 * Gosu 0.16 v Thor's Hammer 2.28 (queen sac) by Graham Banks, CCC, December 06, 2008 » Gosu
 * Jim, do you remember? by Gábor Szots, Winboard Forum, March 26, 2009
 * Re: Jim, do you remember? by Jim Ablett, Winboard Forum, May 24, 2009

=External Links=

Chess Engine

 * Thor's Hammer Home Page archived by the Wayback Machine (June 2006)
 * Index of /chess/engines/Jim Ablett/THORS HAMMER by Jim Ablett, hosted by Kirill Kryukov
 * Thor's Hammer 2.28 32-bit in KCEC
 * Thor's Hammer in CCRL 40/4

Misc

 * Thor's Hammer (disambiguation) from Wikipedia
 * Mjölnir from Wikipedia
 * Mjolnir (comics) from Wikipedia
 * Thor from Wikipedia
 * Hammer from Wikipedia
 * Hammer of Thor (monument) from Wikipedia
 * Thors Hammer - Evasive Dreams Beyond, 1971, YouTube Video

=References= Up one level