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Do all bigram processing here, instead of in updatedb.csh; saves 

a few cycles (it's runs like 2 seconds instead of 16) and the algorithm
is hopefully a bit more clear
This commit is contained in:
jdolecek 2000-03-20 19:17:35 +00:00
parent 41053184b6
commit a46f4702f8
1 changed files with 74 additions and 11 deletions
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85
usr.bin/locate/bigram/locate.bigram.c
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@ -1,4 +1,4 @@
/* $NetBSD: locate.bigram.c,v 1.6 1997/10/19 04:11:52 lukem Exp $ */ /* $NetBSD: locate.bigram.c,v 1.7 2000/03/20 19:17:35 jdolecek Exp $ */
/* /*
* Copyright (c) 1989, 1993 * Copyright (c) 1989, 1993
@ -46,7 +46,7 @@ __COPYRIGHT("@(#) Copyright (c) 1989, 1993\n\
#if 0 #if 0
static char sccsid[] = "@(#)locate.bigram.c 8.2 (Berkeley) 4/28/95"; static char sccsid[] = "@(#)locate.bigram.c 8.2 (Berkeley) 4/28/95";
#endif #endif
__RCSID("$NetBSD: locate.bigram.c,v 1.6 1997/10/19 04:11:52 lukem Exp $"); __RCSID("$NetBSD: locate.bigram.c,v 1.7 2000/03/20 19:17:35 jdolecek Exp $");
#endif /* not lint */ #endif /* not lint */
/* /*
@ -57,12 +57,53 @@ __RCSID("$NetBSD: locate.bigram.c,v 1.6 1997/10/19 04:11:52 lukem Exp $");
*/ */
#include <stdio.h> #include <stdio.h>
#include <stdlib.h>
#include <sys/param.h> /* for MAXPATHLEN */ #include <sys/param.h> /* for MAXPATHLEN */
char buf1[MAXPATHLEN] = " ";
char buf2[MAXPATHLEN];
int main __P((int, char **)); int main __P((int, char **));
static int compare_bigrams __P((const void *, const void *));
static void add_bigram __P((u_char, u_char));
static char buf1[MAXPATHLEN] = " ";
static char buf2[MAXPATHLEN];
struct bigram {
int count;
u_char b1, b2; /* needed for final sorting */
};
struct bigram bigrams[256 * 256];
static void
add_bigram(i1, i2)
u_char i1, i2;
{
if (i1 == '\n') {
bigrams[0].count++;
i1 = 0;
}
if (i2 == '\n') {
bigrams[0].count++;
i2 = i1;
i1 = 0;
}
bigrams[(i1<<8)+i2].count++;
}
static int
compare_bigrams(item1, item2)
const void *item1, *item2;
{
const struct bigram *it1=item1, *it2=item2;
if (it1->count != it2->count)
return it2->count - it1->count;
else if (it1->b1 != it2->b1)
return it2->b1 - it1->b1;
else
return it2->b2 - it2->b2;
}
int int
main(argc, argv) main(argc, argv)
@ -71,6 +112,15 @@ main(argc, argv)
{ {
char *cp; char *cp;
char *oldpath = buf1, *path = buf2; char *oldpath = buf1, *path = buf2;
struct bigram *bg;
int i;
/* initialize bigram array */
memset(bigrams, 0, sizeof(bigrams));
for(i=0; i < 65536; i++) {
bigrams[i].b1 = i / 256;
bigrams[i].b2 = i % 256;
}
while ( fgets ( path, sizeof(buf2), stdin ) != NULL ) { while ( fgets ( path, sizeof(buf2), stdin ) != NULL ) {
@ -78,18 +128,31 @@ main(argc, argv)
for ( cp = path; *cp == *oldpath; cp++, oldpath++ ) for ( cp = path; *cp == *oldpath; cp++, oldpath++ )
if ( *oldpath == '\0' ) if ( *oldpath == '\0' )
break; break;
/* /*
* output post-residue bigrams only * output post-residue bigrams only
*/ */
while ( *cp != '\0' && *(cp + 1) != '\0' ) { for(; cp[0] != '\0' && cp[1] != '\0'; cp += 2)
putchar ( *cp++ ); add_bigram((u_char)cp[0], (u_char)cp[1]);
putchar ( *cp++ );
putchar ( '\n' ); if (path == buf1) /* swap pointers */
}
if ( path == buf1 ) /* swap pointers */
path = buf2, oldpath = buf1; path = buf2, oldpath = buf1;
else else
path = buf1, oldpath = buf2; path = buf1, oldpath = buf2;
} }
/* sort the bigrams by how many times it appeared and their value */
heapsort((void *)bigrams, 256 * 256, sizeof(struct bigram),
compare_bigrams);
/* write 128 most frequent bigrams out */
bg = bigrams;
for (i = 0; i < 128 && bg->count > 0; i++, bg++) {
if (bg->b1 != '\0')
fputc(bg->b1, stdout);
if (bg->b2 != '\0')
fputc(bg->b2, stdout);
}
return (0); return (0);
} }