/* $Id: zvrank.c,v 1.7.2.1 2004/11/04 12:49:36 heikki Exp $
Copyright (C) 1995,1996,1997,1998,1999,2000,2001,2002,2003
Index Data Aps
This file is part of the Zebra server.
Zebra is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 2, or (at your option) any later
version.
Zebra is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received a copy of the GNU General Public License
along with Zebra; see the file LICENSE.zebra. If not, write to the
Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.
*/
/*
Zvrank: an experimental ranking algorithm. See doc/zvrank.txt and
source in index/zvrank.c. Enable this by using rank: zvrank in zebra.cfg.
Contributed by Johannes Leveling <Johannes.Leveling at
fernuni-hagen.de>
*/
/* Zebra Vector Space Model RANKing
**
** six (seven) letter identifier for weighting scheme
** best document weighting:
** tfc nfc (tpc npc) [original naming]
** ntc atc npc apc [SMART naming, used here]
** best query weighting:
** nfx tfx bfx (npx tpx bpx) [original naming]
** atn ntn btn apn npn bpn [SMART naming]
** -> should set zvrank.weighting-scheme to one of
** "ntc-atn", "atc-atn", etc.
*/
#include <math.h> /* for log */
#include <stdio.h>
#include <assert.h>
#ifdef WIN32
#include <io.h>
#else
#include <unistd.h>
#endif
#include "index.h"
static double blog(double x) {
/* log_2, log_e or log_10 is used, best to change it here if necessary */
if (x <= 0)
return 0.0;
return log(x); /* / log(base) */
}
/* structures */
struct rank_class_info { /* now we need this */
int dummy;
char rscheme[8]; /* name of weighting scheme */
};
struct rs_info { /* for result set */
int db_docs; /* number of documents in database (collection) */
int db_terms; /* number of distinct terms in database (debugging?) */
int db_f_max; /* maximum of f_t in database (debugging?) */
char *db_f_max_str; /* string (most frequent term) - for debugging */
/**/
char rscheme[8]; /* name of weighting scheme */
/**/
int veclen;
void (*d_tf_fct)(void *, void *); /* doc term frequency function */
void (*d_idf_fct)(void *, void *); /* doc idf function */
void (*d_norm_fct)(void *, void *); /* doc normalization function */
/**/
void (*q_tf_fct)(void *, void *); /* query term frequency function */
void (*q_idf_fct)(void *, void *); /* query idf function */
void (*q_norm_fct)(void *, void *); /* query normalization function */
double (*sim_fct)(void *, void *); /* similarity function (scoring function) */
struct ds_info *qdoc;
struct ds_info *rdoc;
};
typedef struct rs_info *RS;
static void prn_rs(RS rs) { /* for debugging */
yaz_log(LOG_DEBUG, "* RS:");
yaz_log(LOG_DEBUG, " db_docs: %d", rs->db_docs);
yaz_log(LOG_DEBUG, " db_terms: %d", rs->db_terms);
yaz_log(LOG_DEBUG, " f_max: %d", rs->db_f_max);
yaz_log(LOG_DEBUG, " f_max_str: %s", rs->db_f_max_str);
yaz_log(LOG_DEBUG, " veclen: %d", rs->veclen);
/* rscheme implies functions */
yaz_log(LOG_DEBUG, " rscheme: %s", rs->rscheme);
return;
}
struct ds_info { /* document info */
char *docid; /* unique doc identifier */
int docno; /* doc number */
int doclen; /* document length */
int d_f_max; /* maximum number of any term in doc (needed) */
char *d_f_max_str; /* most frequent term in d - for debugging */
int veclen; /* vector length */
struct ts_info *terms;
double docsim; /* similarity in [0, ..., 1] (= score/1000) */
};
typedef struct ds_info* DS;
#if 0
static void prn_ds(DS ds) { /* for debugging */
yaz_log(LOG_DEBUG, " * DS:");
yaz_log(LOG_DEBUG, " docid: %s", ds->docid);
yaz_log(LOG_DEBUG, " docno: %d", ds->docno);
yaz_log(LOG_DEBUG, " doclen: %d", ds->doclen);
yaz_log(LOG_DEBUG, " d_f_max: %d", ds->d_f_max);
yaz_log(LOG_DEBUG, " d_f_max_str:%s", ds->d_f_max_str);
yaz_log(LOG_DEBUG, " veclen: %d", ds->veclen);
return;
}
#endif
struct ts_info { /* term info */
char *name;
int *id;
/**/
int gocc;
int locc;
double tf;
double idf;
double wt;
};
typedef struct ts_info *TS;
#if 0
static void prn_ts(TS ts) { /* for debugging */
yaz_log(LOG_DEBUG, " * TERM:%s gocc:%d locc:%d tf:%f idf:%f wt:%f",
ts->name, ts->gocc, ts->locc, ts->tf, ts->idf, ts->wt);
return;
}
#endif
/* end structures */
/* *** */
/*
** weighting functions
** check: RS is not needed anymore
*/
/* calculate and store new term frequency vector */
static void tf_none(void *rsi, void *dsi) {
DS ds=(DS)dsi;
int i, veclen, freq;
/* no conversion. 1 <= tf */
veclen=ds->veclen;
for (i=0; i < veclen; i++) {
freq=ds->terms[i].locc;
ds->terms[i].tf=freq;
}
return;
}
static void tf_binary(void *rsi, void *dsi) {
DS ds=(DS)dsi;
int i, veclen, freq;
/* tf in {0, 1} */
veclen=ds->veclen;
for (i=0; i < veclen; i++) {
freq=ds->terms[i].locc;
if (freq > 0)
ds->terms[i].tf=1.0;
else
ds->terms[i].tf=0.0;
}
return;
}
static void tf_max_norm(void *rsi, void *dsi) {
DS ds=(DS)dsi;
double tf_max;
int i, veclen, freq;
/* divide each term by max, so 0 <= tf <= 1 */
tf_max=ds->d_f_max; /* largest frequency of t in document */
veclen=ds->veclen;
for (i=0; i < veclen; i++) {
freq=ds->terms[i].locc;
if ((freq > 0) &&
(tf_max > 0.0))
ds->terms[i].tf=freq/tf_max;
else
ds->terms[i].tf=0.0;
}
return;
}
static void tf_aug_norm(void *rsi, void *dsi) {
DS ds=(DS)dsi;
double K;
double tf_max;
int i, veclen, freq;
/* augmented normalized tf. 0.5 <= tf <= 1 for K = 0.5 */
tf_max=ds->d_f_max; /* largest frequency of t in document */
veclen=ds->veclen;
K=0.5; /* zvrank.const-K */
for (i=0; i < veclen; i++) {
freq=ds->terms[i].locc;
if ((freq > 0) &&
(tf_max > 0.0))
ds->terms[i].tf=K+(1.0-K)*(freq/tf_max);
else
ds->terms[i].tf=0.0;
}
return;
}
static void tf_square(void *rsi, void *dsi) {
DS ds=(DS)dsi;
int i, veclen, freq;
/* tf ^ 2 */
veclen=ds->veclen;
for (i=0; i < veclen; i++) {
freq=ds->terms[i].locc;
if (freq > 0)
ds->terms[i].tf=freq*freq;
else
ds->terms[i].tf=0.0;
}
return;
}
static void tf_log(void *rsi, void *dsi) {
DS ds=(DS)dsi;
int i, veclen, freq;
/* logarithmic tf */
veclen=ds->veclen;
for (i=0; i < veclen; i++) {
freq=ds->terms[i].locc;
if (freq > 0)
ds->terms[i].tf=1.0+blog(freq);
else
ds->terms[i].tf=0.0;
}
return;
}
/* calculate and store inverse document frequency vector */
static void idf_none(void *rsi, void *dsi) {
DS ds=(DS)dsi;
int i, veclen;
/* no conversion */
veclen=ds->veclen;
for (i=0; i < veclen; i++) {
ds->terms[i].idf=1.0;
}
return;
}
static void idf_tfidf(void *rsi, void *dsi) {
RS rs=(RS)rsi;
DS ds=(DS)dsi;
int num_docs, gocc;
int i, veclen;
double idf;
/* normal tfidf weight */
veclen=ds->veclen;
num_docs=rs->db_docs;
for (i=0; i < veclen; i++) {
gocc=ds->terms[i].gocc;
if (gocc==0)
idf=0.0;
else
idf=blog(num_docs/gocc);
ds->terms[i].idf=idf;
}
return;
}
static void idf_prob(void *rsi, void *dsi) {
RS rs=(RS)rsi;
DS ds=(DS)dsi;
int num_docs, gocc;
int i, veclen;
double idf;
/* probabilistic formulation */
veclen=ds->veclen;
num_docs=rs->db_docs;
for (i=0; i < veclen; i++) {
gocc=ds->terms[i].gocc;
if (gocc==0)
idf=0.0;
else
idf=blog((num_docs-gocc)/gocc);
ds->terms[i].idf=idf;
}
return;
}
static void idf_freq(void *rsi, void *dsi) {
RS rs=(RS)rsi;
DS ds=(DS)dsi;
int num_docs;
int i, veclen;
double idf;
/* frequency formulation */
veclen=ds->veclen;
num_docs=rs->db_docs;
if (num_docs==0)
idf=0.0;
else
idf=1.0/num_docs;
for (i=0; i < veclen; i++) {
ds->terms[i].idf=idf;
}
return;
}
static void idf_squared(void *rsi, void *dsi) {
RS rs=(RS)rsi;
DS ds=(DS)dsi;
int num_docs, gocc;
int i, veclen;
double idf;
/* idf ^ 2 */
veclen=ds->veclen;
num_docs=rs->db_docs;
yaz_log(LOG_DEBUG, "idf_squared: db_docs required");
for (i=0; i < veclen; i++) {
gocc=ds->terms[i].gocc;
if (gocc==0)
idf=0.0;
else
idf=blog(num_docs/gocc);
idf=idf*idf;
ds->terms[i].idf=idf;
}
return;
}
/* calculate and store normalized weight (tf-idf) vector */
static void norm_none(void *rsi, void *dsi) {
DS ds=(DS)dsi;
int i, veclen;
/* no normalization */
veclen=ds->veclen;
for (i=0; i < veclen; i++) {
ds->terms[i].wt=ds->terms[i].tf*ds->terms[i].idf;
}
return;
}
static void norm_sum(void *rsi, void *dsi) {
DS ds=(DS)dsi;
int i, veclen;
double tfs=0.0;
/**/
veclen=ds->veclen;
for (i=0; i < veclen; i++) {
ds->terms[i].wt=ds->terms[i].tf*ds->terms[i].idf;
tfs+=ds->terms[i].wt;
}
if (tfs > 0.0)
for (i=0; i < veclen; i++) {
ds->terms[i].wt=ds->terms[i].wt/tfs;
}
/* else: tfs==0 && ds->terms[i].wt==0 */
return;
}
static void norm_cosine(void *rsi, void *dsi) {
DS ds=(DS)dsi;
int i, veclen;
double tfs=0.0;
/**/
veclen=ds->veclen;
for (i=0; i < veclen; i++) {
ds->terms[i].wt=ds->terms[i].tf*ds->terms[i].idf;
tfs+=(ds->terms[i].wt*ds->terms[i].wt);
}
tfs=sqrt(tfs);
if (tfs > 0.0)
for (i=0; i < veclen; i++) {
ds->terms[i].wt=ds->terms[i].wt/tfs;
}
/* else: tfs==0 && ds->terms[i].wt==0 */
return;
}
static void norm_fourth(void *rsi, void *dsi) {
DS ds=(DS)dsi;
int i, veclen;
double tfs=0.0, fr;
/**/
veclen=ds->veclen;
for (i=0; i < veclen; i++) {
ds->terms[i].wt=ds->terms[i].tf*ds->terms[i].idf;
fr=(ds->terms[i].wt*ds->terms[i].wt);
fr=fr*fr; /* ^ 4 */
tfs+=fr;
}
if (tfs > 0.0)
for (i=0; i < veclen; i++) {
ds->terms[i].wt=ds->terms[i].wt/tfs;
}
/* else: tfs==0 && ds->terms[i].wt==0 */
return;
}
static void norm_max(void *rsi, void *dsi) {
DS ds=(DS)dsi;
int i, veclen;
double tfm=0.0;
/**/
veclen=ds->veclen;
for (i=0; i < veclen; i++) {
ds->terms[i].wt=ds->terms[i].tf*ds->terms[i].idf;
if (ds->terms[i].wt > tfm)
tfm=ds->terms[i].wt;
}
if (tfm > 0.0)
for (i=0; i < veclen; i++) {
ds->terms[i].wt=ds->terms[i].wt/tfm;
}
/* else: tfs==0 && ds->terms[i].wt==0 */
return;
}
/* add: norm_pivot, ... */
static double sim_cosine(void *dsi1, void *dsi2) {
DS ds1=(DS)dsi1;
DS ds2=(DS)dsi2;
int i, veclen;
double smul=0.0, sdiv=0.0, sqr11=0.0, sqr22=0.0;
double v1, v2;
/**/
veclen=ds1->veclen; /* and ds2->veclen */
for (i=0; i < veclen; i++) {
v1=ds1->terms[i].wt;
v2=ds2->terms[i].wt;
smul +=(v1*v2);
sqr11+=(v1*v1);
sqr22+=(v2*v2);
}
sdiv=sqrt(sqr11*sqr22);
if (sdiv==0.0)
return 0.0;
return (smul/sdiv);
}
/* add: norm_jaccard, norm_dice, ... */
/* end weighting functions */
/* *** */
static void zv_init_scheme(RS rs, const char *sname) {
int slen;
char c0, c1, c2, c3, c4, c5, c6;
const char *def_rscheme="ntc-atn"; /* a good default */
/**/
yaz_log(LOG_DEBUG, "zv_init_scheme");
slen=strlen(sname);
if (slen < 7)
yaz_log(LOG_LOG, "zvrank: invalid weighting-scheme \"%s\"", sname);
if (slen > 0) c0=sname[0]; else c0=def_rscheme[0];
if (slen > 1) c1=sname[1]; else c1=def_rscheme[1];
if (slen > 2) c2=sname[2]; else c2=def_rscheme[2];
c3='-';
if (slen > 4) c4=sname[4]; else c4=def_rscheme[4];
if (slen > 5) c5=sname[5]; else c5=def_rscheme[5];
if (slen > 6) c6=sname[6]; else c6=def_rscheme[6];
/**/
/* assign doc functions */
switch (c0) {
case 'b':
rs->d_tf_fct=tf_binary;
rs->rscheme[0]='b';
break;
case 'm':
rs->d_tf_fct=tf_max_norm;
rs->rscheme[0]='m';
yaz_log(LOG_DEBUG, "tf_max_norm: d_f_max required");
break;
case 'a':
rs->d_tf_fct=tf_aug_norm;
rs->rscheme[0]='a';
yaz_log(LOG_DEBUG, "tf_aug_norm: d_f_max required");
break;
case 's':
rs->d_tf_fct=tf_square;
rs->rscheme[0]='s';
break;
case 'l':
rs->d_tf_fct=tf_log;
rs->rscheme[0]='l';
break;
default: /* 'n' */
rs->d_tf_fct=tf_none;
rs->rscheme[0]='n';
}
switch (c1) {
case 't':
rs->d_idf_fct=idf_tfidf;
rs->rscheme[1]='t';
yaz_log(LOG_DEBUG, "idf_tfidf: db_docs required");
break;
case 'p':
rs->d_idf_fct=idf_prob;
rs->rscheme[1]='p';
yaz_log(LOG_DEBUG, "idf_prob: db_docs required");
break;
case 'f':
rs->d_idf_fct=idf_freq;
rs->rscheme[1]='f';
yaz_log(LOG_DEBUG, "idf_freq: db_docs required");
break;
case 's':
rs->d_idf_fct=idf_squared;
rs->rscheme[1]='s';
yaz_log(LOG_DEBUG, "idf_squared: db_docs required");
break;
default: /* 'n' */
rs->d_idf_fct=idf_none;
rs->rscheme[1]='n';
}
switch (c2) {
case 's':
rs->d_norm_fct=norm_sum;
rs->rscheme[2]='s';
break;
case 'c':
rs->d_norm_fct=norm_cosine;
rs->rscheme[2]='c';
break;
case 'f':
rs->d_norm_fct=norm_fourth;
rs->rscheme[2]='t';
break;
case 'm':
rs->d_norm_fct=norm_max;
rs->rscheme[2]='m';
break;
default: /* 'n' */
rs->d_norm_fct=norm_none;
rs->rscheme[2]='n';
}
/**/
rs->rscheme[3]='-';
/* assign query functions */
switch (c4) {
case 'b':
rs->q_tf_fct=tf_binary;
rs->rscheme[4]='b';
break;
case 'm':
rs->q_tf_fct=tf_max_norm;
yaz_log(LOG_DEBUG, "tf_max_norm: d_f_max required");
rs->rscheme[4]='m';
break;
case 'a':
rs->q_tf_fct=tf_aug_norm;
rs->rscheme[4]='a';
yaz_log(LOG_DEBUG, "tf_aug_norm: d_f_max required");
break;
case 's':
rs->q_tf_fct=tf_square;
rs->rscheme[4]='s';
break;
case 'l':
rs->q_tf_fct=tf_log;
rs->rscheme[4]='l';
break;
default: /* 'n' */
rs->q_tf_fct=tf_none;
rs->rscheme[4]='n';
}
switch (c5) {
case 't':
rs->q_idf_fct=idf_tfidf;
rs->rscheme[5]='t';
yaz_log(LOG_DEBUG, "idf_tfidf: db_docs required");
break;
case 'p':
rs->q_idf_fct=idf_prob;
rs->rscheme[5]='p';
yaz_log(LOG_DEBUG, "idf_prob: db_docs required");
break;
case 'f':
rs->q_idf_fct=idf_freq;
rs->rscheme[5]='f';
yaz_log(LOG_DEBUG, "idf_freq: db_docs required");
break;
case 's':
rs->q_idf_fct=idf_squared;
rs->rscheme[5]='s';
yaz_log(LOG_DEBUG, "idf_squared: db_docs required");
break;
default: /* 'n' */
rs->q_idf_fct=idf_none;
rs->rscheme[5]='n';
}
switch (c6) {
case 's':
rs->q_norm_fct=norm_sum;
rs->rscheme[6]='s';
break;
case 'c':
rs->q_norm_fct=norm_cosine;
rs->rscheme[6]='c';
break;
case 'f':
rs->q_norm_fct=norm_fourth;
rs->rscheme[6]='f';
break;
case 'm':
rs->q_norm_fct=norm_max;
rs->rscheme[6]='m';
break;
default: /* 'n' */
rs->q_norm_fct=norm_none;
rs->rscheme[6]='n';
}
rs->rscheme[7]='\0';
/**/
rs->sim_fct=sim_cosine;
yaz_log(LOG_DEBUG, "zv_scheme %s", rs->rscheme);
return;
}
static void zv_init(RS rs, const char *rscheme) {
yaz_log(LOG_DEBUG, "zv_init");
/**/
rs->db_docs=100000; /* assign correct value here */
rs->db_terms=500000; /* assign correct value here (for debugging) */
rs->db_f_max=50; /* assign correct value here */
rs->db_f_max_str="a"; /* assign correct value here (for debugging) */
zv_init_scheme(rs, rscheme);
return;
}
/******/
/*
* zv_create: Creates/Initialises this rank handler. This routine is
* called exactly once. The routine returns the class_handle.
*/
static void *zv_create (ZebraHandle zh) {
int i;
Res res = zh->res;
const char *wscheme;
struct rank_class_info *ci = (struct rank_class_info *)
xmalloc (sizeof(*ci));
yaz_log(LOG_DEBUG, "zv_create");
wscheme=res_get_def(res, "zvrank.weighting-scheme", "");
for (i=0; wscheme[i] && i < 8; i++)
ci->rscheme[i]=wscheme[i];
ci->rscheme[i] = '\0';
return ci;
}
/*
* zv_destroy: Destroys this rank handler. This routine is called
* when the handler is no longer needed - i.e. when the server
* dies. The class_handle was previously returned by create.
*/
static void zv_destroy (struct zebra_register *reg, void *class_handle) {
struct rank_class_info *ci = (struct rank_class_info *) class_handle;
yaz_log(LOG_DEBUG, "zv_destroy");
xfree (ci);
}
/*
* zv_begin: Prepares beginning of "real" ranking. Called once for
* each result set. The returned handle is a "set handle" and
* will be used in each of the handlers below.
*/
static void *zv_begin(struct zebra_register *reg, void *class_handle, RSET rset)
{
struct rs_info *rs=(struct rs_info *)xmalloc(sizeof(*rs));
struct rank_class_info *ci=(struct rank_class_info *)class_handle;
int i;
int veclen, gocc;
/**/
yaz_log(LOG_DEBUG, "zv_begin");
veclen=rset->no_rset_terms; /* smaller vector here */
zv_init(rs, ci->rscheme);
rs->veclen=veclen;
prn_rs(rs);
rs->qdoc=(struct ds_info *)xmalloc(sizeof(*rs->qdoc));
rs->qdoc->terms=(struct ts_info *)xmalloc(sizeof(*rs->qdoc->terms)*rs->veclen);
rs->qdoc->veclen=veclen;
rs->qdoc->d_f_max=1; /* no duplicates */
rs->qdoc->d_f_max_str="";
rs->rdoc=(struct ds_info *)xmalloc(sizeof(*rs->rdoc));
rs->rdoc->terms=(struct ts_info *)xmalloc(sizeof(*rs->rdoc->terms)*rs->veclen);
rs->rdoc->veclen=veclen;
rs->rdoc->d_f_max=10; /* just a guess */
rs->rdoc->d_f_max_str="";
/* yaz_log(LOG_DEBUG, "zv_begin_init"); */
for (i = 0; i < rs->veclen; i++)
{
gocc=rset->rset_terms[i]->nn;
/* yaz_log(LOG_DEBUG, "zv_begin_init i=%d gocc=%d", i, gocc); */
rs->qdoc->terms[i].gocc=gocc;
rs->qdoc->terms[i].locc=1; /* assume query has no duplicate terms */
rs->rdoc->terms[i].gocc=gocc;
rs->rdoc->terms[i].locc=0;
}
(*rs->q_tf_fct)(rs, rs->qdoc); /* we do this once only */
(*rs->q_idf_fct)(rs, rs->qdoc);
(*rs->q_norm_fct)(rs, rs->qdoc);
return rs;
}
/*
* zv_end: Terminates ranking process. Called after a result set
* has been ranked.
*/
static void zv_end (struct zebra_register *reg, void *rsi)
{
RS rs=(RS)rsi;
yaz_log(LOG_DEBUG, "zv_end");
xfree(rs->qdoc->terms);
xfree(rs->rdoc->terms);
xfree(rs->qdoc);
xfree(rs->rdoc);
xfree(rs);
return;
}
/*
* zv_add: Called for each word occurence in a result set. This routine
* should be as fast as possible. This routine should "incrementally"
* update the score.
*/
static void zv_add (void *rsi, int seqno, int i) {
RS rs=(RS)rsi;
/* yaz_log(LOG_DEBUG, "zvrank zv_add seqno=%d term_index=%d", seqno, term_index);*/
rs->rdoc->terms[i].locc++;
}
/*
* zv_calc: Called for each document in a result. This handler should
* produce a score based on previous call(s) to the add handler. The
* score should be between 0 and 1000. If score cannot be obtained
* -1 should be returned.
*/
static int zv_calc (void *rsi, int sysno)
{
int i, veclen;
int score=0;
double dscore=0.0;
RS rs=(RS)rsi;
/* yaz_log(LOG_DEBUG, "zv_calc"); */
/**/
veclen=rs->veclen;
if (veclen==0)
return -1;
for (i = 0; i < veclen; i++) {
/* qdoc weight has already been calculated */
(*rs->d_tf_fct)(rs, rs->rdoc);
(*rs->d_idf_fct)(rs, rs->rdoc);
(*rs->d_norm_fct)(rs, rs->rdoc);
dscore=rs->sim_fct(rs->qdoc, rs->rdoc);
}
score = dscore * 1000;
yaz_log (LOG_LOG, "sysno=%d score=%d", sysno, score);
if (score > 1000) /* should not happen */
score = 1000;
/* reset counts for the next record */
for (i = 0; i < rs->veclen; i++)
rs->rdoc->terms[i].locc=0;
return score;
}
/*
* Pseudo-meta code with sequence of calls as they occur in a
* server. Handlers are prefixed by --:
*
* server init
* -- create
* foreach search
* rank result set
* -- begin
* foreach record
* foreach word
* -- add
* -- calc
* -- end
* -- destroy
* server close
*/
static struct rank_control rank_control_vsm = {
"zvrank",
zv_create,
zv_destroy,
zv_begin,
zv_end,
zv_calc,
zv_add,
};
struct rank_control *rankzv_class = &rank_control_vsm;
/* EOF */
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