/***************************************************************************/ /* micro-Max, */ /* A chess program smaller than 2KB (of non-blank source), by H.G. Muller */ /***************************************************************************/ /* version 4.8 (1953 characters) features: */ /* - recursive negamax search */ /* - all-capture MVV/LVA quiescence search */ /* - (internal) iterative deepening */ /* - best-move-first 'sorting' */ /* - a hash table storing score and best move */ /* - futility pruning */ /* - king safety through magnetic, frozen king in middle-game */ /* - R=2 null-move pruning */ /* - keep hash and repetition-draw detection */ /* - better defense against passers through gradual promotion */ /* - extend check evasions in inner nodes */ /* - reduction of all non-Pawn, non-capture moves except hash move (LMR) */ /* - full FIDE rules (expt under-promotion) and move-legality checking */ #define W while #define K(A,B) *(int*)(T+A+(B&8)+S*(B&7)) #define J(A) K(y+A,b[y])-K(x+A,u)-K(H+A,t) #define U (1<<24) struct _ {int K,V;char X,Y,D;} A[U]; /* hash table, 16M+8 entries*/ int M=136,S=128,I=8e3,Q,O,K,N,R,J,Z,k=16,*p,c[9]; /* M=0x88 */ char L, w[]={0,2,2,7,-1,8,12,23}, /* relative piece values */ o[]={-16,-15,-17,0,1,16,0,1,16,15,17,0,14,18,31,33,0, /* step-vector lists */ 7,-1,11,6,8,3,6, /* 1st dir. in o[] per piece*/ 6,3,5,7,4,5,3,6}, /* initial piece setup */ b[129], /* board: half of 16x8+dummy*/ T[1035]; /* hash translation table */ D(q,l,e,E,z,n) /* recursive minimax search, k=moving side, n=depth*/ int q,l,e,E,z,n; /* (q,l)=window, e=current eval. score, E=e.p. sqr.*/ { /* e=score, z=prev.dest; J,Z=hashkeys; return score*/ int j,r,m,v,d,h,i,F,G,V,P,f=J,g=Z,C,s; char t,p,u,x,y,X,Y,H,B; struct _*a=A+(J+k*E&U-1); /* lookup pos. in hash table*/ q--; /* adj. window: delay bonus */ k^=24; /* change sides */ d=a->D;m=a->V;X=a->X;Y=a->Y; /* resume at stored depth */ if(a->K-Z|z| /* miss: other pos. or empty*/ !(m<=q|X&8&&m>=l|X&S)) /* or window incompatible */ d=Y=0; /* start iter. from scratch */ X&=~M; /* start at best-move hint */ W(d++35?d>2?-I:e:-P; /* Prune or stand-pat */ N++; /* node count (for timing) */ do{u=b[x]; /* scan board looking for */ if(u&k) /* own piece (inefficient!)*/ {r=p=u&7; /* p = piece type (set r>0) */ j=o[p+16]; /* first step vector f.piece*/ W(r=p>2&r<0?-r:-o[++j]) /* loop over directions o[] */ {A: /* resume normal after best */ y=x;F=G=S; /* (x,y)=move, (F,G)=castl.R*/ do{ /* y traverses ray, or: */ H=y=h?Y^h:y+r; /* sneak in prev. best move */ if(y&M)break; /* board edge hit */ m=E-S&b[E]&&y-E<2&E-y<2?I:m; /* bad castling */ if(p<3&y==E)H^=16; /* shift capt.sqr. H if e.p.*/ t=b[H];if(t&k|p<3&!(y-x&7)-!t)break; /* capt. own, bad pawn mode */ i=37*w[t&7]+(t&192); /* value of capt. piece t */ m=i<0?I:m; /* K capture */ if(m>=l&d>1)goto C; /* abort on fail high */ v=d-1?e:i-p; /* MVV/LVA scoring */ if(d-!t>1) /* remaining depth */ {v=p<6?b[x+8]-b[y+8]:0; /* center positional pts. */ b[G]=b[H]=b[x]=0;b[y]=u|32; /* do move, set non-virgin */ if(!(G&M))b[F]=k+6,v+=50; /* castling: put R & score */ v-=p-4|R>29?0:20; /* penalize mid-game K move */ if(p<3) /* pawns: */ {v-=9*((x-2&M||b[x-2]-u)+ /* structure, undefended */ (x+2&M||b[x+2]-u)-1 /* squares plus bias */ +(b[x^16]==k+36)) /* kling to non-virgin King */ -(R>>2); /* end-game Pawn-push bonus */ V=y+r+1&S?647-p:2*(u&y+16&32); /* promotion or 6/7th bonus */ b[y]+=V;i+=V; /* change piece, add score */ } v+=e+i;V=m>q?m:q; /* new eval and alpha */ J+=J(0);Z+=J(8)+G-S; /* update hash key */ C=d-1-(d>5&p>2&!t&!h); C=R>29|d<3|P-I?C:d; /* extend 1 ply if in check */ do s=C>2|v>V?-D(-l,-V,-v, /* recursive eval. of reply */ F,0,C):v; /* or fail low if futile */ W(s>q&++CD=99;a->V=0; /* lock game in hash as draw*/ R+=i>>7;return l; /* captured non-P material */ } J=f;Z=g; /* restore hash key */ b[G]=k+6;b[F]=b[y]=0;b[x]=u;b[H]=t; /* undo move,G can be dummy */ } if(v>m) /* new best, update max,best*/ m=v,X=x,Y=y|S&F; /* mark double move with S */ if(h){h=0;goto A;} /* redo after doing old best*/ if(x+r-y|u&32| /* not 1st step,moved before*/ p>2&(p-4|j-7|| /* no P & no lateral K move,*/ b[G=x+3^r>>1&7]-k-6 /* no virgin R in corner G, */ ||b[G^1]|b[G^2]) /* no 2 empty sq. next to R */ )t+=p<5; /* fake capt. for nonsliding*/ else F=y; /* enable e.p. */ }W(!t); /* if not capt. continue ray*/ }}}W((x=x+9&~M)-B); /* next sqr. of board, wrap */ C:if(m>I-M|mD<99) /* protect game history */ a->K=Z,a->V=m,a->D=d, /* always store in hash tab */ a->X=X|8*(m>q)|S*(mY=Y; /* move, type (bound/exact),*/ /*if(z)printf("%2d ply, %9d searched, score=%6d by %c%c%c%c\n",d-1,N-S,m, 'a'+(X&7),'8'-(X>>4),'a'+(Y&7),'8'-(Y>>4&7)); /* uncomment for Kibitz */ } /* encoded in X S,8 bits */ k^=24; /* change sides back */ return m+=mM)T[N]=rand()>>9; W(1) /* play loop */ {N=-1;W(++N<121) printf("%c",N&8&&(N+=7)?10:".?+nkbrq?*?NKBRQ"[b[N]&15]); /* print board */ p=c;W((*p++=getchar())>10); /* read input line */ K=I; /* invalid move */ if(*c-10)K=*c-16*c[1]+799,L=c[2]-16*c[3]+799; /* parse entered move */ D(-I,I,Q,O,1,3); /* think or check & do*/ } }