Thanks to John Cummings.

src/cmd/upas/bayes/bayes.c

@@ -0,0 +1,232 @@
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+#include <regexp.h>
+#include "hash.h"
+
+enum
+{
+	MAXTAB = 256,
+	MAXBEST = 32,
+};
+
+typedef struct Table Table;
+struct Table
+{
+	char *file;
+	Hash *hash;
+	int nmsg;
+};
+
+typedef struct Word Word;
+struct Word
+{
+	Stringtab *s;	/* from hmsg */
+	int count[MAXTAB];	/* counts from each table */
+	double p[MAXTAB];	/* probabilities from each table */
+	double mp;	/* max probability */
+	int mi;		/* w.p[w.mi] = w.mp */
+};
+
+Table tab[MAXTAB];
+int ntab;
+
+Word best[MAXBEST];
+int mbest;
+int nbest;
+
+int debug;
+
+void
+usage(void)
+{
+	fprint(2, "usage: bayes [-D] [-m maxword] boxhash ... ~ msghash ...\n");
+	exits("usage");
+}
+
+void*
+emalloc(int n)
+{
+	void *v;
+
+	v = mallocz(n, 1);
+	if(v == nil)
+		sysfatal("out of memory");
+	return v;
+}
+
+void
+noteword(Word *w)
+{
+	int i;
+
+	for(i=nbest-1; i>=0; i--)
+		if(w->mp < best[i].mp)
+			break;
+	i++;
+
+	if(i >= mbest)
+		return;
+	if(nbest == mbest)
+		nbest--;
+	if(i < nbest)
+		memmove(&best[i+1], &best[i], (nbest-i)*sizeof(best[0]));
+	best[i] = *w;
+	nbest++;
+}
+
+Hash*
+hread(char *s)
+{
+	Hash *h;
+	Biobuf *b;
+
+	if((b = Bopenlock(s, OREAD)) == nil)
+		sysfatal("open %s: %r", s);
+
+	h = emalloc(sizeof(Hash));
+	Breadhash(b, h, 1);
+	Bterm(b);
+	return h;
+}
+
+void
+main(int argc, char **argv)
+{
+	int i, j, a, mi, oi, tot, keywords;
+	double totp, p, xp[MAXTAB];
+	Hash *hmsg;
+	Word w;
+	Stringtab *s, *t;
+	Biobuf bout;
+
+	mbest = 15;
+	keywords = 0;
+	ARGBEGIN{
+	case 'D':
+		debug = 1;
+		break;
+	case 'k':
+		keywords = 1;
+		break;
+	case 'm':
+		mbest = atoi(EARGF(usage()));
+		if(mbest > MAXBEST)
+			sysfatal("cannot keep more than %d words", MAXBEST);
+		break;
+	default:
+		usage();
+	}ARGEND
+
+	for(i=0; i<argc; i++)
+		if(strcmp(argv[i], "~") == 0)
+			break;
+
+	if(i > MAXTAB)
+		sysfatal("cannot handle more than %d tables", MAXTAB);
+
+	if(i+1 >= argc)
+		usage();
+
+	for(i=0; i<argc; i++){
+		if(strcmp(argv[i], "~") == 0)
+			break;
+		tab[ntab].file = argv[i];
+		tab[ntab].hash = hread(argv[i]);
+		s = findstab(tab[ntab].hash, "*nmsg*", 6, 1);
+		if(s == nil || s->count == 0)
+			tab[ntab].nmsg = 1;
+		else
+			tab[ntab].nmsg = s->count;
+		ntab++;
+	}
+
+	Binit(&bout, 1, OWRITE);
+
+	oi = ++i;
+	for(a=i; a<argc; a++){
+		hmsg = hread(argv[a]);
+		nbest = 0;
+		for(s=hmsg->all; s; s=s->link){
+			w.s = s;
+			tot = 0;
+			totp = 0.0;
+			for(i=0; i<ntab; i++){
+				t = findstab(tab[i].hash, s->str, s->n, 0);
+				if(t == nil)
+					w.count[i] = 0;
+				else
+					w.count[i] = t->count;
+				tot += w.count[i];
+				p = w.count[i]/(double)tab[i].nmsg;
+				if(p >= 1.0)
+					p = 1.0;
+				w.p[i] = p;
+				totp += p;
+			}
+
+			if(tot < 5){		/* word does not appear enough; give to box 0 */
+				w.p[0] = 0.5;
+				for(i=1; i<ntab; i++)
+					w.p[i] = 0.1;
+				w.mp = 0.5;
+				w.mi = 0;
+				noteword(&w);
+				continue;
+			}
+
+			w.mp = 0.0;
+			for(i=0; i<ntab; i++){
+				p = w.p[i];
+				p /= totp;
+				if(p < 0.01)
+					p = 0.01;
+				else if(p > 0.99)
+					p = 0.99;
+				if(p > w.mp){
+					w.mp = p;
+					w.mi = i;
+				}
+				w.p[i] = p;
+			}
+			noteword(&w);
+		}
+
+		totp = 0.0;
+		for(i=0; i<ntab; i++){
+			p = 1.0;
+			for(j=0; j<nbest; j++)
+				p *= best[j].p[i];
+			xp[i] = p;
+			totp += p;
+		}
+		for(i=0; i<ntab; i++)
+			xp[i] /= totp;
+		mi = 0;
+		for(i=1; i<ntab; i++)
+			if(xp[i] > xp[mi])
+				mi = i;
+		if(oi != argc-1)
+			Bprint(&bout, "%s: ", argv[a]);
+		Bprint(&bout, "%s %f", tab[mi].file, xp[mi]);
+		if(keywords){
+			for(i=0; i<nbest; i++){
+				Bprint(&bout, " ");
+				Bwrite(&bout, best[i].s->str, best[i].s->n);
+				Bprint(&bout, " %f", best[i].p[mi]);
+			}
+		}
+		freehash(hmsg);
+		Bprint(&bout, "\n");
+		if(debug){
+			for(i=0; i<nbest; i++){
+				Bwrite(&bout, best[i].s->str, best[i].s->n);
+				Bprint(&bout, " %f", best[i].p[mi]);
+				if(best[i].p[mi] < best[i].mp)
+					Bprint(&bout, " (%f %s)", best[i].mp, tab[best[i].mi].file);
+				Bprint(&bout, "\n");
+			}
+		}
+	}
+	Bterm(&bout);
+}