Import of 4.4BSD-Lite2 source

1 files changed, 1479 insertions, 0 deletions

diff --git a/gomoku/pickmove.c b/gomoku/pickmove.c
new file mode 100644
index 00000000..197d3c5c
--- /dev/null
+++ b/gomoku/pickmove.c
@@ -0,0 +1,1479 @@
+/*
+ * Copyright (c) 1994
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Ralph Campbell.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef lint
+static char sccsid[] = "@(#)pickmove.c	8.2 (Berkeley) 5/3/95";
+#endif /* not lint */
+
+#include <stdio.h>
+#include <curses.h>
+#include <machine/limits.h>
+
+#include "gomoku.h"
+
+#define BITS_PER_INT	(sizeof(int) * CHAR_BIT)
+#define MAPSZ		(BAREA / BITS_PER_INT)
+
+#define BIT_SET(a, b)	((a)[(b)/BITS_PER_INT] |= (1 << ((b) % BITS_PER_INT)))
+#define BIT_CLR(a, b)	((a)[(b)/BITS_PER_INT] &= ~(1 << ((b) % BITS_PER_INT)))
+#define BIT_TEST(a, b)	((a)[(b)/BITS_PER_INT] & (1 << ((b) % BITS_PER_INT)))
+
+struct	combostr *hashcombos[FAREA];	/* hash list for finding duplicates */
+struct	combostr *sortcombos;		/* combos at higher levels */
+int	combolen;			/* number of combos in sortcombos */
+int	nextcolor;			/* color of next move */
+int	elistcnt;			/* count of struct elist allocated */
+int	combocnt;			/* count of struct combostr allocated */
+int	forcemap[MAPSZ];		/* map for blocking <1,x> combos */
+int	tmpmap[MAPSZ];			/* map for blocking <1,x> combos */
+int	nforce;				/* count of opponent <1,x> combos */
+
+pickmove(us)
+	int us;
+{
+	register struct spotstr *sp, *sp1, *sp2;
+	register union comboval *Ocp, *Tcp;
+	char *str;
+	int i, j, m;
+
+	/* first move is easy */
+	if (movenum == 1)
+		return (PT(K,10));
+
+	/* initialize all the board values */
+	for (sp = &board[PT(T,20)]; --sp >= &board[PT(A,1)]; ) {
+		sp->s_combo[BLACK].s = MAXCOMBO + 1;
+		sp->s_combo[WHITE].s = MAXCOMBO + 1;
+		sp->s_level[BLACK] = 255;
+		sp->s_level[WHITE] = 255;
+		sp->s_nforce[BLACK] = 0;
+		sp->s_nforce[WHITE] = 0;
+		sp->s_flg &= ~(FFLAGALL | MFLAGALL);
+	}
+	nforce = 0;
+	memset(forcemap, 0, sizeof(forcemap));
+
+	/* compute new values */
+	nextcolor = us;
+	scanframes(BLACK);
+	scanframes(WHITE);
+
+	/* find the spot with the highest value */
+	for (sp = sp1 = sp2 = &board[PT(T,19)]; --sp >= &board[PT(A,1)]; ) {
+		if (sp->s_occ != EMPTY)
+			continue;
+		if (debug && (sp->s_combo[BLACK].c.a == 1 ||
+		    sp->s_combo[WHITE].c.a == 1)) {
+			sprintf(fmtbuf, "- %s %x/%d %d %x/%d %d %d", stoc(sp - board),
+				sp->s_combo[BLACK].s, sp->s_level[BLACK],
+				sp->s_nforce[BLACK],
+				sp->s_combo[WHITE].s, sp->s_level[WHITE],
+				sp->s_nforce[WHITE],
+				sp->s_wval);
+			dlog(fmtbuf);
+		}
+		/* pick the best black move */
+		if (better(sp, sp1, BLACK))
+			sp1 = sp;
+		/* pick the best white move */
+		if (better(sp, sp2, WHITE))
+			sp2 = sp;
+	}
+
+	if (debug) {
+		sprintf(fmtbuf, "B %s %x/%d %d %x/%d %d %d %d",
+			stoc(sp1 - board),
+			sp1->s_combo[BLACK].s, sp1->s_level[BLACK],
+			sp1->s_nforce[BLACK],
+			sp1->s_combo[WHITE].s, sp1->s_level[WHITE],
+			sp1->s_nforce[WHITE], sp1->s_wval);
+		dlog(fmtbuf);
+		sprintf(fmtbuf, "W %s %x/%d %d %x/%d %d %d %d",
+			stoc(sp2 - board),
+			sp2->s_combo[WHITE].s, sp2->s_level[WHITE],
+			sp2->s_nforce[WHITE],
+			sp2->s_combo[BLACK].s, sp2->s_level[BLACK],
+			sp2->s_nforce[BLACK], sp2->s_wval);
+		dlog(fmtbuf);
+		/*
+		 * Check for more than one force that can't
+		 * all be blocked with one move.
+		 */
+		sp = (us == BLACK) ? sp2 : sp1;
+		m = sp - board;
+		if (sp->s_combo[!us].c.a == 1 && !BIT_TEST(forcemap, m))
+			dlog("*** Can't be blocked");
+	}
+	if (us == BLACK) {
+		Ocp = &sp1->s_combo[BLACK];
+		Tcp = &sp2->s_combo[WHITE];
+	} else {
+		Tcp = &sp1->s_combo[BLACK];
+		Ocp = &sp2->s_combo[WHITE];
+		sp = sp1;
+		sp1 = sp2;
+		sp2 = sp;
+	}
+	/*
+	 * Block their combo only if we have to (i.e., if they are one move
+	 * away from completing a force and we don't have a force that
+	 * we can complete which takes fewer moves to win).
+	 */
+	if (Tcp->c.a <= 1 && (Ocp->c.a > 1 ||
+	    Tcp->c.a + Tcp->c.b < Ocp->c.a + Ocp->c.b))
+		return (sp2 - board);
+	return (sp1 - board);
+}
+
+/*
+ * Return true if spot 'sp' is better than spot 'sp1' for color 'us'.
+ */
+better(sp, sp1, us)
+	struct spotstr *sp;
+	struct spotstr *sp1;
+	int us;
+{
+	int them, s, s1;
+
+	if (sp->s_combo[us].s < sp1->s_combo[us].s)
+		return (1);
+	if (sp->s_combo[us].s != sp1->s_combo[us].s)
+		return (0);
+	if (sp->s_level[us] < sp1->s_level[us])
+		return (1);
+	if (sp->s_level[us] != sp1->s_level[us])
+		return (0);
+	if (sp->s_nforce[us] > sp1->s_nforce[us])
+		return (1);
+	if (sp->s_nforce[us] != sp1->s_nforce[us])
+		return (0);
+
+	them = !us;
+	s = sp - board;
+	s1 = sp1 - board;
+	if (BIT_TEST(forcemap, s) && !BIT_TEST(forcemap, s1))
+		return (1);
+	if (!BIT_TEST(forcemap, s) && BIT_TEST(forcemap, s1))
+		return (0);
+	if (sp->s_combo[them].s < sp1->s_combo[them].s)
+		return (1);
+	if (sp->s_combo[them].s != sp1->s_combo[them].s)
+		return (0);
+	if (sp->s_level[them] < sp1->s_level[them])
+		return (1);
+	if (sp->s_level[them] != sp1->s_level[them])
+		return (0);
+	if (sp->s_nforce[them] > sp1->s_nforce[them])
+		return (1);
+	if (sp->s_nforce[them] != sp1->s_nforce[them])
+		return (0);
+
+	if (sp->s_wval > sp1->s_wval)
+		return (1);
+	if (sp->s_wval != sp1->s_wval)
+		return (0);
+
+#ifdef SVR4
+	return (rand() & 1);
+#else
+	return (random() & 1);
+#endif
+}
+
+int	curcolor;	/* implicit parameter to makecombo() */
+int	curlevel;	/* implicit parameter to makecombo() */
+
+/*
+ * Scan the sorted list of non-empty frames and
+ * update the minimum combo values for each empty spot.
+ * Also, try to combine frames to find more complex (chained) moves.
+ */
+scanframes(color)
+	int color;
+{
+	register struct combostr *cbp, *ecbp;
+	register struct spotstr *sp;
+	register union comboval *cp;
+	register struct elist *ep, *nep;
+	register int i, r, d, n;
+	union comboval cb;
+
+	curcolor = color;
+
+	/* check for empty list of frames */
+	cbp = sortframes[color];
+	if (cbp == (struct combostr *)0)
+		return;
+
+	/* quick check for four in a row */
+	sp = &board[cbp->c_vertex];
+	cb.s = sp->s_fval[color][d = cbp->c_dir].s;
+	if (cb.s < 0x101) {
+		d = dd[d];
+		for (i = 5 + cb.c.b; --i >= 0; sp += d) {
+			if (sp->s_occ != EMPTY)
+				continue;
+			sp->s_combo[color].s = cb.s;
+			sp->s_level[color] = 1;
+		}
+		return;
+	}
+
+	/*
+	 * Update the minimum combo value for each spot in the frame
+	 * and try making all combinations of two frames intersecting at
+	 * an empty spot.
+	 */
+	n = combolen;
+	ecbp = cbp;
+	do {
+		sp = &board[cbp->c_vertex];
+		cp = &sp->s_fval[color][r = cbp->c_dir];
+		d = dd[r];
+		if (cp->c.b) {
+			/*
+			 * Since this is the first spot of an open ended
+			 * frame, we treat it as a closed frame.
+			 */
+			cb.c.a = cp->c.a + 1;
+			cb.c.b = 0;
+			if (cb.s < sp->s_combo[color].s) {
+				sp->s_combo[color].s = cb.s;
+				sp->s_level[color] = 1;
+			}
+			/*
+			 * Try combining other frames that intersect
+			 * at this spot.
+			 */
+			makecombo2(cbp, sp, 0, cb.s);
+			if (cp->s != 0x101)
+				cb.s = cp->s;
+			else if (color != nextcolor)
+				memset(tmpmap, 0, sizeof(tmpmap));
+			sp += d;
+			i = 1;
+		} else {
+			cb.s = cp->s;
+			i = 0;
+		}
+		for (; i < 5; i++, sp += d) {	/* for each spot */
+			if (sp->s_occ != EMPTY)
+				continue;
+			if (cp->s < sp->s_combo[color].s) {
+				sp->s_combo[color].s = cp->s;
+				sp->s_level[color] = 1;
+			}
+			if (cp->s == 0x101) {
+				sp->s_nforce[color]++;
+				if (color != nextcolor) {
+					n = sp - board;
+					BIT_SET(tmpmap, n);
+				}
+			}
+			/*
+			 * Try combining other frames that intersect
+			 * at this spot.
+			 */
+			makecombo2(cbp, sp, i, cb.s);
+		}
+		if (cp->s == 0x101 && color != nextcolor) {
+			if (nforce == 0)
+				memcpy(forcemap, tmpmap, sizeof(tmpmap));
+			else {
+				for (i = 0; i < MAPSZ; i++)
+					forcemap[i] &= tmpmap[i];
+			}
+		}
+		/* mark frame as having been processed */
+		board[cbp->c_vertex].s_flg |= MFLAG << r;
+	} while ((cbp = cbp->c_next) != ecbp);
+
+	/*
+	 * Try to make new 3rd level combos, 4th level, etc.
+	 * Limit the search depth early in the game.
+	 */
+	d = 2;
+	while (d <= ((movenum + 1) >> 1) && combolen > n) {
+		if (debug) {
+			sprintf(fmtbuf, "%cL%d %d %d %d", "BW"[color],
+				d, combolen - n, combocnt, elistcnt);
+			dlog(fmtbuf);
+			refresh();
+		}
+		n = combolen;
+		addframes(d);
+		d++;
+	}
+
+	/* scan for combos at empty spots */
+	for (sp = &board[PT(T,20)]; --sp >= &board[PT(A,1)]; ) {
+		for (ep = sp->s_empty; ep; ep = nep) {
+			cbp = ep->e_combo;
+			if (cbp->c_combo.s <= sp->s_combo[color].s) {
+				if (cbp->c_combo.s != sp->s_combo[color].s) {
+					sp->s_combo[color].s = cbp->c_combo.s;
+					sp->s_level[color] = cbp->c_nframes;
+				} else if (cbp->c_nframes < sp->s_level[color])
+					sp->s_level[color] = cbp->c_nframes;
+			}
+			nep = ep->e_next;
+			free(ep);
+			elistcnt--;
+		}
+		sp->s_empty = (struct elist *)0;
+		for (ep = sp->s_nempty; ep; ep = nep) {
+			cbp = ep->e_combo;
+			if (cbp->c_combo.s <= sp->s_combo[color].s) {
+				if (cbp->c_combo.s != sp->s_combo[color].s) {
+					sp->s_combo[color].s = cbp->c_combo.s;
+					sp->s_level[color] = cbp->c_nframes;
+				} else if (cbp->c_nframes < sp->s_level[color])
+					sp->s_level[color] = cbp->c_nframes;
+			}
+			nep = ep->e_next;
+			free(ep);
+			elistcnt--;
+		}
+		sp->s_nempty = (struct elist *)0;
+	}
+
+	/* remove old combos */
+	if ((cbp = sortcombos) != (struct combostr *)0) {
+		struct combostr *ncbp;
+
+		/* scan the list */
+		ecbp = cbp;
+		do {
+			ncbp = cbp->c_next;
+			free(cbp);
+			combocnt--;
+		} while ((cbp = ncbp) != ecbp);
+		sortcombos = (struct combostr *)0;
+	}
+	combolen = 0;
+
+#ifdef DEBUG
+	if (combocnt) {
+		sprintf(fmtbuf, "scanframes: %c combocnt %d", "BW"[color],
+			combocnt);
+		dlog(fmtbuf);
+		whatsup(0);
+	}
+	if (elistcnt) {
+		sprintf(fmtbuf, "scanframes: %c elistcnt %d", "BW"[color],
+			elistcnt);
+		dlog(fmtbuf);
+		whatsup(0);
+	}
+#endif
+}
+
+/*
+ * Compute all level 2 combos of frames intersecting spot 'osp'
+ * within the frame 'ocbp' and combo value 's'.
+ */
+makecombo2(ocbp, osp, off, s)
+	struct combostr *ocbp;
+	struct spotstr *osp;
+	int off;
+	int s;
+{
+	register struct spotstr *sp, *fsp;
+	register struct combostr *ncbp;
+	register int f, r, d, c;
+	int baseB, fcnt, emask, bmask, n;
+	union comboval ocb, fcb;
+	struct combostr **scbpp, *fcbp;
+
+	/* try to combine a new frame with those found so far */
+	ocb.s = s;
+	baseB = ocb.c.a + ocb.c.b - 1;
+	fcnt = ocb.c.a - 2;
+	emask = fcnt ? ((ocb.c.b ? 0x1E : 0x1F) & ~(1 << off)) : 0;
+	for (r = 4; --r >= 0; ) {			/* for each direction */
+	    /* don't include frames that overlap in the same direction */
+	    if (r == ocbp->c_dir)
+		continue;
+	    d = dd[r];
+	    /*
+	     * Frame A combined with B is the same value as B combined with A
+	     * so skip frames that have already been processed (MFLAG).
+	     * Also skip blocked frames (BFLAG) and frames that are <1,x>
+	     * since combining another frame with it isn't valid.
+	     */
+	    bmask = (BFLAG | FFLAG | MFLAG) << r;
+	    fsp = osp;
+	    for (f = 0; f < 5; f++, fsp -= d) {		/* for each frame */
+		if (fsp->s_occ == BORDER)
+		    break;
+		if (fsp->s_flg & bmask)
+		    continue;
+
+		/* don't include frames of the wrong color */
+		fcb.s = fsp->s_fval[curcolor][r].s;
+		if (fcb.c.a >= MAXA)
+		    continue;
+
+		/*
+		 * Get the combo value for this frame.
+		 * If this is the end point of the frame,
+		 * use the closed ended value for the frame.
+		 */
+		if (f == 0 && fcb.c.b || fcb.s == 0x101) {
+		    fcb.c.a++;
+		    fcb.c.b = 0;
+		}
+
+		/* compute combo value */
+		c = fcb.c.a + ocb.c.a - 3;
+		if (c > 4)
+		    continue;
+		n = fcb.c.a + fcb.c.b - 1;
+		if (baseB < n)
+		    n = baseB;
+
+		/* make a new combo! */
+		ncbp = (struct combostr *)malloc(sizeof(struct combostr) +
+		    2 * sizeof(struct combostr *));
+		scbpp = (struct combostr **)(ncbp + 1);
+		fcbp = fsp->s_frame[r];
+		if (ocbp < fcbp) {
+		    scbpp[0] = ocbp;
+		    scbpp[1] = fcbp;
+		} else {
+		    scbpp[0] = fcbp;
+		    scbpp[1] = ocbp;
+		}
+		ncbp->c_combo.c.a = c;
+		ncbp->c_combo.c.b = n;
+		ncbp->c_link[0] = ocbp;
+		ncbp->c_link[1] = fcbp;
+		ncbp->c_linkv[0].s = ocb.s;
+		ncbp->c_linkv[1].s = fcb.s;
+		ncbp->c_voff[0] = off;
+		ncbp->c_voff[1] = f;
+		ncbp->c_vertex = osp - board;
+		ncbp->c_nframes = 2;
+		ncbp->c_dir = 0;
+		ncbp->c_frameindex = 0;
+		ncbp->c_flg = (ocb.c.b) ? C_OPEN_0 : 0;
+		if (fcb.c.b)
+		    ncbp->c_flg |= C_OPEN_1;
+		ncbp->c_framecnt[0] = fcnt;
+		ncbp->c_emask[0] = emask;
+		ncbp->c_framecnt[1] = fcb.c.a - 2;
+		ncbp->c_emask[1] = ncbp->c_framecnt[1] ?
+		    ((fcb.c.b ? 0x1E : 0x1F) & ~(1 << f)) : 0;
+		combocnt++;
+
+		if (c == 1 && debug > 1 || debug > 3) {
+		    sprintf(fmtbuf, "%c c %d %d m %x %x o %d %d",
+			"bw"[curcolor],
+			ncbp->c_framecnt[0], ncbp->c_framecnt[1],
+			ncbp->c_emask[0], ncbp->c_emask[1],
+			ncbp->c_voff[0], ncbp->c_voff[1]);
+		    dlog(fmtbuf);
+		    printcombo(ncbp, fmtbuf);
+		    dlog(fmtbuf);
+		}
+		if (c > 1) {
+		    /* record the empty spots that will complete this combo */
+		    makeempty(ncbp);
+
+		    /* add the new combo to the end of the list */
+		    appendcombo(ncbp, curcolor);
+		} else {
+		    updatecombo(ncbp, curcolor);
+		    free(ncbp);
+		    combocnt--;
+		}
+#ifdef DEBUG
+		if (c == 1 && debug > 1 || debug > 5) {
+		    markcombo(ncbp);
+		    bdisp();
+		    whatsup(0);
+		    clearcombo(ncbp, 0);
+		}
+#endif /* DEBUG */
+	    }
+	}
+}
+
+/*
+ * Scan the sorted list of frames and try to add a frame to
+ * combinations of 'level' number of frames.
+ */
+addframes(level)
+	int level;
+{
+	register struct combostr *cbp, *ecbp;
+	register struct spotstr *sp, *fsp;
+	register struct elist *ep, *nep;
+	register int i, r, d;
+	struct combostr **cbpp, *pcbp;
+	union comboval fcb, cb;
+
+	curlevel = level;
+
+	/* scan for combos at empty spots */
+	i = curcolor;
+	for (sp = &board[PT(T,20)]; --sp >= &board[PT(A,1)]; ) {
+		for (ep = sp->s_empty; ep; ep = nep) {
+			cbp = ep->e_combo;
+			if (cbp->c_combo.s <= sp->s_combo[i].s) {
+				if (cbp->c_combo.s != sp->s_combo[i].s) {
+					sp->s_combo[i].s = cbp->c_combo.s;
+					sp->s_level[i] = cbp->c_nframes;
+				} else if (cbp->c_nframes < sp->s_level[i])
+					sp->s_level[i] = cbp->c_nframes;
+			}
+			nep = ep->e_next;
+			free(ep);
+			elistcnt--;
+		}
+		sp->s_empty = sp->s_nempty;
+		sp->s_nempty = (struct elist *)0;
+	}
+
+	/* try to add frames to the uncompleted combos at level curlevel */
+	cbp = ecbp = sortframes[curcolor];
+	do {
+		fsp = &board[cbp->c_vertex];
+		r = cbp->c_dir;
+		/* skip frames that are part of a <1,x> combo */
+		if (fsp->s_flg & (FFLAG << r))
+			continue;
+
+		/*
+		 * Don't include <1,x> combo frames,
+		 * treat it as a closed three in a row instead.
+		 */
+		fcb.s = fsp->s_fval[curcolor][r].s;
+		if (fcb.s == 0x101)
+			fcb.s = 0x200;
+
+		/*
+		 * If this is an open ended frame, use
+		 * the combo value with the end closed.
+		 */
+		if (fsp->s_occ == EMPTY) {
+			if (fcb.c.b) {
+				cb.c.a = fcb.c.a + 1;
+				cb.c.b = 0;
+			} else
+				cb.s = fcb.s;
+			makecombo(cbp, fsp, 0, cb.s);
+		}
+
+		/*
+		 * The next four spots are handled the same for both
+		 * open and closed ended frames.
+		 */
+		d = dd[r];
+		sp = fsp + d;
+		for (i = 1; i < 5; i++, sp += d) {
+			if (sp->s_occ != EMPTY)
+				continue;
+			makecombo(cbp, sp, i, fcb.s);
+		}
+	} while ((cbp = cbp->c_next) != ecbp);
+
+	/* put all the combos in the hash list on the sorted list */
+	cbpp = &hashcombos[FAREA];
+	do {
+		cbp = *--cbpp;
+		if (cbp == (struct combostr *)0)
+			continue;
+		*cbpp = (struct combostr *)0;
+		ecbp = sortcombos;
+		if (ecbp == (struct combostr *)0)
+			sortcombos = cbp;
+		else {
+			/* append to sort list */
+			pcbp = ecbp->c_prev;
+			pcbp->c_next = cbp;
+			ecbp->c_prev = cbp->c_prev;
+			cbp->c_prev->c_next = ecbp;
+			cbp->c_prev = pcbp;
+		}
+	} while (cbpp != hashcombos);
+}
+
+/*
+ * Compute all level N combos of frames intersecting spot 'osp'
+ * within the frame 'ocbp' and combo value 's'.
+ */
+makecombo(ocbp, osp, off, s)
+	struct combostr *ocbp;
+	struct spotstr *osp;
+	int off;
+	int s;
+{
+	register struct combostr *cbp, *ncbp;
+	register struct spotstr *sp;
+	register struct elist *ep;
+	register int n, c;
+	struct elist *nep, **epp;
+	struct combostr **scbpp;
+	int baseB, fcnt, emask, verts, d;
+	union comboval ocb, cb;
+	struct ovlp_info vertices[1];
+
+	ocb.s = s;
+	baseB = ocb.c.a + ocb.c.b - 1;
+	fcnt = ocb.c.a - 2;
+	emask = fcnt ? ((ocb.c.b ? 0x1E : 0x1F) & ~(1 << off)) : 0;
+	for (ep = osp->s_empty; ep; ep = ep->e_next) {
+	    /* check for various kinds of overlap */
+	    cbp = ep->e_combo;
+	    verts = checkframes(cbp, ocbp, osp, s, vertices);
+	    if (verts < 0)
+		continue;
+
+	    /* check to see if this frame forms a valid loop */
+	    if (verts) {
+		sp = &board[vertices[0].o_intersect];
+#ifdef DEBUG
+		if (sp->s_occ != EMPTY) {
+		    sprintf(fmtbuf, "loop: %c %s", "BW"[curcolor],
+			stoc(sp - board));
+		    dlog(fmtbuf);
+		    whatsup(0);
+		}
+#endif
+		/*
+		 * It is a valid loop if the intersection spot
+		 * of the frame we are trying to attach is one
+		 * of the completion spots of the combostr
+		 * we are trying to attach the frame to.
+		 */
+		for (nep = sp->s_empty; nep; nep = nep->e_next) {
+		    if (nep->e_combo == cbp)
+			goto fnd;
+		    if (nep->e_combo->c_nframes < cbp->c_nframes)
+			break;
+		}
+		/* frame overlaps but not at a valid spot */
+		continue;
+	    fnd:
+		;
+	    }
+
+	    /* compute the first half of the combo value */
+	    c = cbp->c_combo.c.a + ocb.c.a - verts - 3;
+	    if (c > 4)
+		continue;
+
+	    /* compute the second half of the combo value */
+	    n = ep->e_fval.c.a + ep->e_fval.c.b - 1;
+	    if (baseB < n)
+		n = baseB;
+
+	    /* make a new combo! */
+	    ncbp = (struct combostr *)malloc(sizeof(struct combostr) +
+		(cbp->c_nframes + 1) * sizeof(struct combostr *));
+	    scbpp = (struct combostr **)(ncbp + 1);
+	    if (sortcombo(scbpp, (struct combostr **)(cbp + 1), ocbp)) {
+		free(ncbp);
+		continue;
+	    }
+	    combocnt++;
+
+	    ncbp->c_combo.c.a = c;
+	    ncbp->c_combo.c.b = n;
+	    ncbp->c_link[0] = cbp;
+	    ncbp->c_link[1] = ocbp;
+	    ncbp->c_linkv[1].s = ocb.s;
+	    ncbp->c_voff[1] = off;
+	    ncbp->c_vertex = osp - board;
+	    ncbp->c_nframes = cbp->c_nframes + 1;
+	    ncbp->c_flg = ocb.c.b ? C_OPEN_1 : 0;
+	    ncbp->c_frameindex = ep->e_frameindex;
+	    /*
+	     * Update the completion spot mask of the frame we
+	     * are attaching 'ocbp' to so the intersection isn't
+	     * listed twice.
+	     */
+	    ncbp->c_framecnt[0] = ep->e_framecnt;
+	    ncbp->c_emask[0] = ep->e_emask;
+	    if (verts) {
+		ncbp->c_flg |= C_LOOP;
+		ncbp->c_dir = vertices[0].o_frameindex;
+		ncbp->c_framecnt[1] = fcnt - 1;
+		if (ncbp->c_framecnt[1]) {
+		    n = (vertices[0].o_intersect - ocbp->c_vertex) /
+			dd[ocbp->c_dir];
+		    ncbp->c_emask[1] = emask & ~(1 << n);
+		} else
+		    ncbp->c_emask[1] = 0;
+		ncbp->c_voff[0] = vertices[0].o_off;
+	    } else {
+		ncbp->c_dir = 0;
+		ncbp->c_framecnt[1] = fcnt;
+		ncbp->c_emask[1] = emask;
+		ncbp->c_voff[0] = ep->e_off;
+	    }
+
+	    if (c == 1 && debug > 1 || debug > 3) {
+		sprintf(fmtbuf, "%c v%d i%d d%d c %d %d m %x %x o %d %d",
+		    "bw"[curcolor], verts, ncbp->c_frameindex, ncbp->c_dir,
+		    ncbp->c_framecnt[0], ncbp->c_framecnt[1],
+		    ncbp->c_emask[0], ncbp->c_emask[1],
+		    ncbp->c_voff[0], ncbp->c_voff[1]);
+		dlog(fmtbuf);
+		printcombo(ncbp, fmtbuf);
+		dlog(fmtbuf);
+	    }
+	    if (c > 1) {
+		/* record the empty spots that will complete this combo */
+		makeempty(ncbp);
+		combolen++;
+	    } else {
+		/* update board values */
+		updatecombo(ncbp, curcolor);
+	    }
+#ifdef DEBUG
+	    if (c == 1 && debug > 1 || debug > 4) {
+		markcombo(ncbp);
+		bdisp();
+		whatsup(0);
+		clearcombo(ncbp, 0);
+	    }
+#endif /* DEBUG */
+	}
+}
+
+#define MAXDEPTH	100
+struct elist	einfo[MAXDEPTH];
+struct combostr	*ecombo[MAXDEPTH];	/* separate from elist to save space */
+
+/*
+ * Add the combostr 'ocbp' to the empty spots list for each empty spot
+ * in 'ocbp' that will complete the combo.
+ */
+makeempty(ocbp)
+	struct combostr *ocbp;
+{
+	struct combostr *cbp, *tcbp, **cbpp;
+	struct elist *ep, *nep, **epp;
+	struct spotstr *sp;
+	int s, d, m, emask, i;
+	int nframes;
+
+	if (debug > 2) {
+		sprintf(fmtbuf, "E%c ", "bw"[curcolor]);
+		printcombo(ocbp, fmtbuf + 3);
+		dlog(fmtbuf);
+	}
+
+	/* should never happen but check anyway */
+	if ((nframes = ocbp->c_nframes) >= MAXDEPTH)
+		return;
+
+	/*
+	 * The lower level combo can be pointed to by more than one
+	 * higher level 'struct combostr' so we can't modify the
+	 * lower level. Therefore, higher level combos store the
+	 * real mask of the lower level frame in c_emask[0] and the
+	 * frame number in c_frameindex.
+	 *
+	 * First we traverse the tree from top to bottom and save the
+	 * connection info. Then we traverse the tree from bottom to
+	 * top overwriting lower levels with the newer emask information.
+	 */
+	ep = &einfo[nframes];
+	cbpp = &ecombo[nframes];
+	for (cbp = ocbp; tcbp = cbp->c_link[1]; cbp = cbp->c_link[0]) {
+		ep--;
+		ep->e_combo = cbp;
+		*--cbpp = cbp->c_link[1];
+		ep->e_off = cbp->c_voff[1];
+		ep->e_frameindex = cbp->c_frameindex;
+		ep->e_fval.s = cbp->c_linkv[1].s;
+		ep->e_framecnt = cbp->c_framecnt[1];
+		ep->e_emask = cbp->c_emask[1];
+	}
+	cbp = ep->e_combo;
+	ep--;
+	ep->e_combo = cbp;
+	*--cbpp = cbp->c_link[0];
+	ep->e_off = cbp->c_voff[0];
+	ep->e_frameindex = 0;
+	ep->e_fval.s = cbp->c_linkv[0].s;
+	ep->e_framecnt = cbp->c_framecnt[0];
+	ep->e_emask = cbp->c_emask[0];
+
+	/* now update the emask info */
+	s = 0;
+	for (i = 2, ep += 2; i < nframes; i++, ep++) {
+		cbp = ep->e_combo;
+		nep = &einfo[ep->e_frameindex];
+		nep->e_framecnt = cbp->c_framecnt[0];
+		nep->e_emask = cbp->c_emask[0];
+
+		if (cbp->c_flg & C_LOOP) {
+			s++;
+			/*
+			 * Account for the fact that this frame connects
+			 * to a previous one (thus forming a loop).
+			 */
+			nep = &einfo[cbp->c_dir];
+			if (--nep->e_framecnt)
+				nep->e_emask &= ~(1 << cbp->c_voff[0]);
+			else
+				nep->e_emask = 0;
+		}
+	}
+
+	/*
+	 * We only need to update the emask values of "complete" loops
+	 * to include the intersection spots.
+	 */
+	if (s && ocbp->c_combo.c.a == 2) {
+		/* process loops from the top down */
+		ep = &einfo[nframes];
+		do {
+			ep--;
+			cbp = ep->e_combo;
+			if (!(cbp->c_flg & C_LOOP))
+				continue;
+
+			/*
+			 * Update the emask values to include the
+			 * intersection spots.
+			 */
+			nep = &einfo[cbp->c_dir];
+			nep->e_framecnt = 1;
+			nep->e_emask = 1 << cbp->c_voff[0];
+			ep->e_framecnt = 1;
+			ep->e_emask = 1 << ep->e_off;
+			ep = &einfo[ep->e_frameindex];
+			do {
+				ep->e_framecnt = 1;
+				ep->e_emask = 1 << ep->e_off;
+				ep = &einfo[ep->e_frameindex];
+			} while (ep > nep);
+		} while (ep != einfo);
+	}
+
+	/* check all the frames for completion spots */
+	for (i = 0, ep = einfo, cbpp = ecombo; i < nframes; i++, ep++, cbpp++) {
+		/* skip this frame if there are no incomplete spots in it */
+		if ((emask = ep->e_emask) == 0)
+			continue;
+		cbp = *cbpp;
+		sp = &board[cbp->c_vertex];
+		d = dd[cbp->c_dir];
+		for (s = 0, m = 1; s < 5; s++, sp += d, m <<= 1) {
+			if (sp->s_occ != EMPTY || !(emask & m))
+				continue;
+
+			/* add the combo to the list of empty spots */
+			nep = (struct elist *)malloc(sizeof(struct elist));
+			nep->e_combo = ocbp;
+			nep->e_off = s;
+			nep->e_frameindex = i;
+			if (ep->e_framecnt > 1) {
+				nep->e_framecnt = ep->e_framecnt - 1;
+				nep->e_emask = emask & ~m;
+			} else {
+				nep->e_framecnt = 0;
+				nep->e_emask = 0;
+			}
+			nep->e_fval.s = ep->e_fval.s;
+			if (debug > 2) {
+				sprintf(fmtbuf, "e %s o%d i%d c%d m%x %x",
+					stoc(sp - board),
+					nep->e_off,
+					nep->e_frameindex,
+					nep->e_framecnt,
+					nep->e_emask,
+					nep->e_fval.s);
+				dlog(fmtbuf);
+			}
+
+			/* sort by the number of frames in the combo */
+			nep->e_next = sp->s_nempty;
+			sp->s_nempty = nep;
+			elistcnt++;
+		}
+	}
+}
+
+/*
+ * Update the board value based on the combostr.
+ * This is called only if 'cbp' is a <1,x> combo.
+ * We handle things differently depending on whether the next move
+ * would be trying to "complete" the combo or trying to block it.
+ */
+updatecombo(cbp, color)
+	struct combostr *cbp;
+	int color;
+{
+	register struct framestr *fp;
+	register struct spotstr *sp;
+	register struct combostr *tcbp;
+	register int i, d;
+	int nframes, flg, s;
+	union comboval cb;
+
+	/* save the top level value for the whole combo */
+	cb.c.a = cbp->c_combo.c.a;
+	nframes = cbp->c_nframes;
+
+	if (color != nextcolor)
+		memset(tmpmap, 0, sizeof(tmpmap));
+
+	for (; tcbp = cbp->c_link[1]; cbp = cbp->c_link[0]) {
+		flg = cbp->c_flg;
+		cb.c.b = cbp->c_combo.c.b;
+		if (color == nextcolor) {
+			/* update the board value for the vertex */
+			sp = &board[cbp->c_vertex];
+			sp->s_nforce[color]++;
+			if (cb.s <= sp->s_combo[color].s) {
+				if (cb.s != sp->s_combo[color].s) {
+					sp->s_combo[color].s = cb.s;
+					sp->s_level[color] = nframes;
+				} else if (nframes < sp->s_level[color])
+					sp->s_level[color] = nframes;
+			}
+		} else {
+			/* update the board values for each spot in frame */
+			sp = &board[s = tcbp->c_vertex];
+			d = dd[tcbp->c_dir];
+			i = (flg & C_OPEN_1) ? 6 : 5;
+			for (; --i >= 0; sp += d, s += d) {
+				if (sp->s_occ != EMPTY)
+					continue;
+				sp->s_nforce[color]++;
+				if (cb.s <= sp->s_combo[color].s) {
+					if (cb.s != sp->s_combo[color].s) {
+						sp->s_combo[color].s = cb.s;
+						sp->s_level[color] = nframes;
+					} else if (nframes < sp->s_level[color])
+						sp->s_level[color] = nframes;
+				}
+				BIT_SET(tmpmap, s);
+			}
+		}
+
+		/* mark the frame as being part of a <1,x> combo */
+		board[tcbp->c_vertex].s_flg |= FFLAG << tcbp->c_dir;
+	}
+
+	if (color != nextcolor) {
+		/* update the board values for each spot in frame */
+		sp = &board[s = cbp->c_vertex];
+		d = dd[cbp->c_dir];
+		i = (flg & C_OPEN_0) ? 6 : 5;
+		for (; --i >= 0; sp += d, s += d) {
+			if (sp->s_occ != EMPTY)
+				continue;
+			sp->s_nforce[color]++;
+			if (cb.s <= sp->s_combo[color].s) {
+				if (cb.s != sp->s_combo[color].s) {
+					sp->s_combo[color].s = cb.s;
+					sp->s_level[color] = nframes;
+				} else if (nframes < sp->s_level[color])
+					sp->s_level[color] = nframes;
+			}
+			BIT_SET(tmpmap, s);
+		}
+		if (nforce == 0)
+			memcpy(forcemap, tmpmap, sizeof(tmpmap));
+		else {
+			for (i = 0; i < MAPSZ; i++)
+				forcemap[i] &= tmpmap[i];
+		}
+		nforce++;
+	}
+
+	/* mark the frame as being part of a <1,x> combo */
+	board[cbp->c_vertex].s_flg |= FFLAG << cbp->c_dir;
+}
+
+/*
+ * Add combo to the end of the list.
+ */
+appendcombo(cbp, color)
+	struct combostr *cbp;
+	int color;
+{
+	struct combostr *pcbp, *ncbp;
+
+	combolen++;
+	ncbp = sortcombos;
+	if (ncbp == (struct combostr *)0) {
+		sortcombos = cbp;
+		cbp->c_next = cbp;
+		cbp->c_prev = cbp;
+		return;
+	}
+	pcbp = ncbp->c_prev;
+	cbp->c_next = ncbp;
+	cbp->c_prev = pcbp;
+	ncbp->c_prev = cbp;
+	pcbp->c_next = cbp;
+}
+
+/*
+ * Return zero if it is valid to combine frame 'fcbp' with the frames
+ * in 'cbp' and forms a linked chain of frames (i.e., a tree; no loops).
+ * Return positive if combining frame 'fcbp' to the frames in 'cbp'
+ * would form some kind of valid loop. Also return the intersection spots
+ * in 'vertices[]' beside the known intersection at spot 'osp'.
+ * Return -1 if 'fcbp' should not be combined with 'cbp'.
+ * 's' is the combo value for frame 'fcpb'.
+ */
+checkframes(cbp, fcbp, osp, s, vertices)
+	struct combostr *cbp;
+	struct combostr *fcbp;
+	struct spotstr *osp;
+	int s;
+	struct ovlp_info *vertices;
+{
+	struct combostr *tcbp, *lcbp;
+	int i, n, mask, flg, verts, loop, index, fcnt;
+	union comboval cb;
+	u_char *str;
+	short *ip;
+
+	cb.s = s;
+	fcnt = cb.c.a - 2;
+	verts = 0;
+	loop = 0;
+	index = cbp->c_nframes;
+	n = (fcbp - frames) * FAREA;
+	str = &overlap[n];
+	ip = &intersect[n];
+	/*
+	 * i == which overlap bit to test based on whether 'fcbp' is
+	 * an open or closed frame.
+	 */
+	i = cb.c.b ? 2 : 0;
+	for (; tcbp = cbp->c_link[1]; lcbp = cbp, cbp = cbp->c_link[0]) {
+		if (tcbp == fcbp)
+			return (-1);	/* fcbp is already included */
+
+		/* check for intersection of 'tcbp' with 'fcbp' */
+		index--;
+		mask = str[tcbp - frames];
+		flg = cbp->c_flg;
+		n = i + ((flg & C_OPEN_1) != 0);
+		if (mask & (1 << n)) {
+			/*
+			 * The two frames are not independent if they
+			 * both lie in the same line and intersect at
+			 * more than one point.
+			 */
+			if (tcbp->c_dir == fcbp->c_dir && (mask & (0x10 << n)))
+				return (-1);
+			/*
+			 * If this is not the spot we are attaching
+			 * 'fcbp' to and it is a reasonable intersection
+			 * spot, then there might be a loop.
+			 */
+			n = ip[tcbp - frames];
+			if (osp != &board[n]) {
+				/* check to see if this is a valid loop */
+				if (verts)
+					return (-1);
+				if (fcnt == 0 || cbp->c_framecnt[1] == 0)
+					return (-1);
+				/*
+				 * Check to be sure the intersection is not
+				 * one of the end points if it is an open
+				 * ended frame.
+				 */
+				if ((flg & C_OPEN_1) &&
+				    (n == tcbp->c_vertex ||
+				     n == tcbp->c_vertex + 5 * dd[tcbp->c_dir]))
+					return (-1);	/* invalid overlap */
+				if (cb.c.b &&
+				    (n == fcbp->c_vertex ||
+				     n == fcbp->c_vertex + 5 * dd[fcbp->c_dir]))
+					return (-1);	/* invalid overlap */
+
+				vertices->o_intersect = n;
+				vertices->o_fcombo = cbp;
+				vertices->o_link = 1;
+				vertices->o_off = (n - tcbp->c_vertex) /
+					dd[tcbp->c_dir];
+				vertices->o_frameindex = index;
+				verts++;
+			}
+		}
+		n = i + ((flg & C_OPEN_0) != 0);
+	}
+	if (cbp == fcbp)
+		return (-1);	/* fcbp is already included */
+
+	/* check for intersection of 'cbp' with 'fcbp' */
+	mask = str[cbp - frames];
+	if (mask & (1 << n)) {
+		/*
+		 * The two frames are not independent if they
+		 * both lie in the same line and intersect at
+		 * more than one point.
+		 */
+		if (cbp->c_dir == fcbp->c_dir && (mask & (0x10 << n)))
+			return (-1);
+		/*
+		 * If this is not the spot we are attaching
+		 * 'fcbp' to and it is a reasonable intersection
+		 * spot, then there might be a loop.
+		 */
+		n = ip[cbp - frames];
+		if (osp != &board[n]) {
+			/* check to see if this is a valid loop */
+			if (verts)
+				return (-1);
+			if (fcnt == 0 || lcbp->c_framecnt[0] == 0)
+				return (-1);
+			/*
+			 * Check to be sure the intersection is not
+			 * one of the end points if it is an open
+			 * ended frame.
+			 */
+			if ((flg & C_OPEN_0) &&
+			    (n == cbp->c_vertex ||
+			     n == cbp->c_vertex + 5 * dd[cbp->c_dir]))
+				return (-1);	/* invalid overlap */
+			if (cb.c.b &&
+			    (n == fcbp->c_vertex ||
+			     n == fcbp->c_vertex + 5 * dd[fcbp->c_dir]))
+				return (-1);	/* invalid overlap */
+
+			vertices->o_intersect = n;
+			vertices->o_fcombo = lcbp;
+			vertices->o_link = 0;
+			vertices->o_off = (n - cbp->c_vertex) /
+				dd[cbp->c_dir];
+			vertices->o_frameindex = 0;
+			verts++;
+		}
+	}
+	return (verts);
+}
+
+/*
+ * Merge sort the frame 'fcbp' and the sorted list of frames 'cbpp' and
+ * store the result in 'scbpp'. 'curlevel' is the size of the 'cbpp' array.
+ * Return true if this list of frames is already in the hash list.
+ * Otherwise, add the new combo to the hash list.
+ */
+sortcombo(scbpp, cbpp, fcbp)
+	struct combostr **scbpp;
+	struct combostr **cbpp;
+	struct combostr *fcbp;
+{
+	struct combostr **spp, **cpp;
+	struct combostr *cbp, *ecbp;
+	int n, inx;
+
+#ifdef DEBUG
+	if (debug > 3) {
+		char *str;
+
+		sprintf(fmtbuf, "sortc: %s%c l%d", stoc(fcbp->c_vertex),
+			pdir[fcbp->c_dir], curlevel);
+		dlog(fmtbuf);
+		str = fmtbuf;
+		for (cpp = cbpp; cpp < cbpp + curlevel; cpp++) {
+			sprintf(str, " %s%c", stoc((*cpp)->c_vertex),
+				pdir[(*cpp)->c_dir]);
+			str += strlen(str);
+		}
+		dlog(fmtbuf);
+	}
+#endif /* DEBUG */
+
+	/* first build the new sorted list */
+	n = curlevel + 1;
+	spp = scbpp + n;
+	cpp = cbpp + curlevel;
+	do {
+		cpp--;
+		if (fcbp > *cpp) {
+			*--spp = fcbp;
+			do
+				*--spp = *cpp;
+			while (cpp-- != cbpp);
+			goto inserted;
+		}
+		*--spp = *cpp;
+	} while (cpp != cbpp);
+	*--spp = fcbp;
+inserted:
+
+	/* now check to see if this list of frames has already been seen */
+	cbp = hashcombos[inx = *scbpp - frames];
+	if (cbp == (struct combostr *)0) {
+		/*
+		 * Easy case, this list hasn't been seen.
+		 * Add it to the hash list.
+		 */
+		fcbp = (struct combostr *)
+			((char *)scbpp - sizeof(struct combostr));
+		hashcombos[inx] = fcbp;
+		fcbp->c_next = fcbp->c_prev = fcbp;
+		return (0);
+	}
+	ecbp = cbp;
+	do {
+		cbpp = (struct combostr **)(cbp + 1);
+		cpp = cbpp + n;
+		spp = scbpp + n;
+		cbpp++;	/* first frame is always the same */
+		do {
+			if (*--spp != *--cpp)
+				goto next;
+		} while (cpp != cbpp);
+		/* we found a match */
+#ifdef DEBUG
+		if (debug > 3) {
+			char *str;
+
+			sprintf(fmtbuf, "sort1: n%d", n);
+			dlog(fmtbuf);
+			str = fmtbuf;
+			for (cpp = scbpp; cpp < scbpp + n; cpp++) {
+				sprintf(str, " %s%c", stoc((*cpp)->c_vertex),
+					pdir[(*cpp)->c_dir]);
+				str += strlen(str);
+			}
+			dlog(fmtbuf);
+			printcombo(cbp, fmtbuf);
+			dlog(fmtbuf);
+			str = fmtbuf;
+			cbpp--;
+			for (cpp = cbpp; cpp < cbpp + n; cpp++) {
+				sprintf(str, " %s%c", stoc((*cpp)->c_vertex),
+					pdir[(*cpp)->c_dir]);
+				str += strlen(str);
+			}
+			dlog(fmtbuf);
+		}
+#endif /* DEBUG */
+		return (1);
+	next:
+		;
+	} while ((cbp = cbp->c_next) != ecbp);
+	/*
+	 * This list of frames hasn't been seen.
+	 * Add it to the hash list.
+	 */
+	ecbp = cbp->c_prev;
+	fcbp = (struct combostr *)((char *)scbpp - sizeof(struct combostr));
+	fcbp->c_next = cbp;
+	fcbp->c_prev = ecbp;
+	cbp->c_prev = fcbp;
+	ecbp->c_next = fcbp;
+	return (0);
+}
+
+/*
+ * Print the combo into string 'str'.
+ */
+printcombo(cbp, str)
+	struct combostr *cbp;
+	char *str;
+{
+	struct combostr *tcbp;
+
+	sprintf(str, "%x/%d", cbp->c_combo.s, cbp->c_nframes);
+	str += strlen(str);
+	for (; tcbp = cbp->c_link[1]; cbp = cbp->c_link[0]) {
+		sprintf(str, " %s%c%x", stoc(tcbp->c_vertex), pdir[tcbp->c_dir],
+			cbp->c_flg);
+		str += strlen(str);
+	}
+	sprintf(str, " %s%c", stoc(cbp->c_vertex), pdir[cbp->c_dir]);
+}
+
+#ifdef DEBUG
+markcombo(ocbp)
+	struct combostr *ocbp;
+{
+	struct combostr *cbp, *tcbp, **cbpp;
+	struct elist *ep, *nep, **epp;
+	struct spotstr *sp;
+	int s, d, m, i;
+	int nframes;
+	int r, n, flg, cmask, omask;
+
+	/* should never happen but check anyway */
+	if ((nframes = ocbp->c_nframes) >= MAXDEPTH)
+		return;
+
+	/*
+	 * The lower level combo can be pointed to by more than one
+	 * higher level 'struct combostr' so we can't modify the
+	 * lower level. Therefore, higher level combos store the
+	 * real mask of the lower level frame in c_emask[0] and the
+	 * frame number in c_frameindex.
+	 *
+	 * First we traverse the tree from top to bottom and save the
+	 * connection info. Then we traverse the tree from bottom to
+	 * top overwriting lower levels with the newer emask information.
+	 */
+	ep = &einfo[nframes];
+	cbpp = &ecombo[nframes];
+	for (cbp = ocbp; tcbp = cbp->c_link[1]; cbp = cbp->c_link[0]) {
+		ep--;
+		ep->e_combo = cbp;
+		*--cbpp = cbp->c_link[1];
+		ep->e_off = cbp->c_voff[1];
+		ep->e_frameindex = cbp->c_frameindex;
+		ep->e_fval.s = cbp->c_linkv[1].s;
+		ep->e_framecnt = cbp->c_framecnt[1];
+		ep->e_emask = cbp->c_emask[1];
+	}
+	cbp = ep->e_combo;
+	ep--;
+	ep->e_combo = cbp;
+	*--cbpp = cbp->c_link[0];
+	ep->e_off = cbp->c_voff[0];
+	ep->e_frameindex = 0;
+	ep->e_fval.s = cbp->c_linkv[0].s;
+	ep->e_framecnt = cbp->c_framecnt[0];
+	ep->e_emask = cbp->c_emask[0];
+
+	/* now update the emask info */
+	s = 0;
+	for (i = 2, ep += 2; i < nframes; i++, ep++) {
+		cbp = ep->e_combo;
+		nep = &einfo[ep->e_frameindex];
+		nep->e_framecnt = cbp->c_framecnt[0];
+		nep->e_emask = cbp->c_emask[0];
+
+		if (cbp->c_flg & C_LOOP) {
+			s++;
+			/*
+			 * Account for the fact that this frame connects
+			 * to a previous one (thus forming a loop).
+			 */
+			nep = &einfo[cbp->c_dir];
+			if (--nep->e_framecnt)
+				nep->e_emask &= ~(1 << cbp->c_voff[0]);
+			else
+				nep->e_emask = 0;
+		}
+	}
+
+	/*
+	 * We only need to update the emask values of "complete" loops
+	 * to include the intersection spots.
+	 */
+	if (s && ocbp->c_combo.c.a == 2) {
+		/* process loops from the top down */
+		ep = &einfo[nframes];
+		do {
+			ep--;
+			cbp = ep->e_combo;
+			if (!(cbp->c_flg & C_LOOP))
+				continue;
+
+			/*
+			 * Update the emask values to include the
+			 * intersection spots.
+			 */
+			nep = &einfo[cbp->c_dir];
+			nep->e_framecnt = 1;
+			nep->e_emask = 1 << cbp->c_voff[0];
+			ep->e_framecnt = 1;
+			ep->e_emask = 1 << ep->e_off;
+			ep = &einfo[ep->e_frameindex];
+			do {
+				ep->e_framecnt = 1;
+				ep->e_emask = 1 << ep->e_off;
+				ep = &einfo[ep->e_frameindex];
+			} while (ep > nep);
+		} while (ep != einfo);
+	}
+
+	/* mark all the frames with the completion spots */
+	for (i = 0, ep = einfo, cbpp = ecombo; i < nframes; i++, ep++, cbpp++) {
+		m = ep->e_emask;
+		cbp = *cbpp;
+		sp = &board[cbp->c_vertex];
+		d = dd[s = cbp->c_dir];
+		cmask = CFLAG << s;
+		omask = (IFLAG | CFLAG) << s;
+		s = ep->e_fval.c.b ? 6 : 5;
+		for (; --s >= 0; sp += d, m >>= 1)
+			sp->s_flg |= (m & 1) ? omask : cmask;
+	}
+}
+
+clearcombo(cbp, open)
+	struct combostr *cbp;
+	int open;
+{
+	register struct spotstr *sp;
+	struct combostr *tcbp;
+	int d, n, mask;
+
+	for (; tcbp = cbp->c_link[1]; cbp = cbp->c_link[0]) {
+		clearcombo(tcbp, cbp->c_flg & C_OPEN_1);
+		open = cbp->c_flg & C_OPEN_0;
+	}
+	sp = &board[cbp->c_vertex];
+	d = dd[n = cbp->c_dir];
+	mask = ~((IFLAG | CFLAG) << n);
+	n = open ? 6 : 5;
+	for (; --n >= 0; sp += d)
+		sp->s_flg &= mask;
+}
+
+list_eq(scbpp, cbpp, n)
+	struct combostr **scbpp;
+	struct combostr **cbpp;
+	int n;
+{
+	struct combostr **spp, **cpp;
+
+	spp = scbpp + n;
+	cpp = cbpp + n;
+	do {
+		if (*--spp != *--cpp)
+			return (0);
+	} while (cpp != cbpp);
+	/* we found a match */
+	return (1);
+}
+#endif /* DEBUG */