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Stemmer and a query interface.

Changeset d556e745d230

Parent f651a75b0efa

by Rup Palchowdhury

Changes to 4 files · Browse files at d556e745d230 Showing diff from parent f651a75b0efa Diff from another changeset...

Change 1 of 1 Show Entire File porter.c Stacked
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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+ +/* This is the Porter stemming algorithm, coded up as thread-safe ANSI C + by the author. + + It may be be regarded as cononical, in that it follows the algorithm + presented in + + Porter, 1980, An algorithm for suffix stripping, Program, Vol. 14, + no. 3, pp 130-137, + + only differing from it at the points marked --DEPARTURE-- below. + + See also http://www.tartarus.org/~martin/PorterStemmer + + The algorithm as described in the paper could be exactly replicated + by adjusting the points of DEPARTURE, but this is barely necessary, + because (a) the points of DEPARTURE are definitely improvements, and + (b) no encoding of the Porter stemmer I have seen is anything like + as exact as this version, even with the points of DEPARTURE! + + You can compile it on Unix with 'gcc -O3 -o stem stem.c' after which + 'stem' takes a list of inputs and sends the stemmed equivalent to + stdout. + + The algorithm as encoded here is particularly fast. + + Release 1: the basic non-thread safe version + + Release 2: this thread-safe version + + Release 3: 11 Apr 2013, fixes the bug noted by Matt Patenaude (see the + basic version for details) + + Release 4: 25 Mar 2014, fixes the bug noted by Klemens Baum (see the + basic version for details) +*/ + +#include <stdlib.h> /* for malloc, free */ +#include <string.h> /* for memcmp, memmove */ +#include "stemmer.h" + +/* The main part of the stemming algorithm starts here. +*/ + +#define TRUE 1 +#define FALSE 0 + +/* stemmer is a structure for a few local bits of data, +*/ + +struct stemmer { + char * b; /* buffer for word to be stemmed */ + int k; /* offset to the end of the string */ + int j; /* a general offset into the string */ +}; + + +/* Member b is a buffer holding a word to be stemmed. The letters are in + b[0], b[1] ... ending at b[z->k]. Member k is readjusted downwards as + the stemming progresses. Zero termination is not in fact used in the + algorithm. + + Note that only lower case sequences are stemmed. Forcing to lower case + should be done before stem(...) is called. + + + Typical usage is: + + struct stemmer * z = create_stemmer(); + char b[] = "pencils"; + int res = stem(z, b, 6); + /- stem the 7 characters of b[0] to b[6]. The result, res, + will be 5 (the 's' is removed). -/ + free_stemmer(z); +*/ + + +extern struct stemmer * create_stemmer(void) +{ + return (struct stemmer *) malloc(sizeof(struct stemmer)); + /* assume malloc succeeds */ +} + +extern void free_stemmer(struct stemmer * z) +{ + free(z); +} + + +/* cons(z, i) is TRUE <=> b[i] is a consonant. ('b' means 'z->b', but here + and below we drop 'z->' in comments. +*/ + +static int cons(struct stemmer * z, int i) +{ switch (z->b[i]) + { case 'a': case 'e': case 'i': case 'o': case 'u': return FALSE; + case 'y': return (i == 0) ? TRUE : !cons(z, i - 1); + default: return TRUE; + } +} + +/* m(z) measures the number of consonant sequences between 0 and j. if c is + a consonant sequence and v a vowel sequence, and <..> indicates arbitrary + presence, + + <c><v> gives 0 + <c>vc<v> gives 1 + <c>vcvc<v> gives 2 + <c>vcvcvc<v> gives 3 + .... +*/ + +static int m(struct stemmer * z) +{ int n = 0; + int i = 0; + int j = z->j; + while(TRUE) + { if (i > j) return n; + if (! cons(z, i)) break; i++; + } + i++; + while(TRUE) + { while(TRUE) + { if (i > j) return n; + if (cons(z, i)) break; + i++; + } + i++; + n++; + while(TRUE) + { if (i > j) return n; + if (! cons(z, i)) break; + i++; + } + i++; + } +} + +/* vowelinstem(z) is TRUE <=> 0,...j contains a vowel */ + +static int vowelinstem(struct stemmer * z) +{ + int j = z->j; + int i; for (i = 0; i <= j; i++) if (! cons(z, i)) return TRUE; + return FALSE; +} + +/* doublec(z, j) is TRUE <=> j,(j-1) contain a double consonant. */ + +static int doublec(struct stemmer * z, int j) +{ + char * b = z->b; + if (j < 1) return FALSE; + if (b[j] != b[j - 1]) return FALSE; + return cons(z, j); +} + +/* cvc(z, i) is TRUE <=> i-2,i-1,i has the form consonant - vowel - consonant + and also if the second c is not w,x or y. this is used when trying to + restore an e at the end of a short word. e.g. + + cav(e), lov(e), hop(e), crim(e), but + snow, box, tray. + +*/ + +static int cvc(struct stemmer * z, int i) +{ if (i < 2 || !cons(z, i) || cons(z, i - 1) || !cons(z, i - 2)) return FALSE; + { int ch = z->b[i]; + if (ch == 'w' || ch == 'x' || ch == 'y') return FALSE; + } + return TRUE; +} + +/* ends(z, s) is TRUE <=> 0,...k ends with the string s. */ + +static int ends(struct stemmer * z, char * s) +{ int length = s[0]; + char * b = z->b; + int k = z->k; + if (s[length] != b[k]) return FALSE; /* tiny speed-up */ + if (length > k + 1) return FALSE; + if (memcmp(b + k - length + 1, s + 1, length) != 0) return FALSE; + z->j = k-length; + return TRUE; +} + +/* setto(z, s) sets (j+1),...k to the characters in the string s, readjusting + k. */ + +static void setto(struct stemmer * z, char * s) +{ int length = s[0]; + int j = z->j; + memmove(z->b + j + 1, s + 1, length); + z->k = j+length; +} + +/* r(z, s) is used further down. */ + +static void r(struct stemmer * z, char * s) { if (m(z) > 0) setto(z, s); } + +/* step1ab(z) gets rid of plurals and -ed or -ing. e.g. + + caresses -> caress + ponies -> poni + ties -> ti + caress -> caress + cats -> cat + + feed -> feed + agreed -> agree + disabled -> disable + + matting -> mat + mating -> mate + meeting -> meet + milling -> mill + messing -> mess + + meetings -> meet + +*/ + +static void step1ab(struct stemmer * z) +{ + char * b = z->b; + if (b[z->k] == 's') + { if (ends(z, "\04" "sses")) z->k -= 2; else + if (ends(z, "\03" "ies")) setto(z, "\01" "i"); else + if (b[z->k - 1] != 's') z->k--; + } + if (ends(z, "\03" "eed")) { if (m(z) > 0) z->k--; } else + if ((ends(z, "\02" "ed") || ends(z, "\03" "ing")) && vowelinstem(z)) + { z->k = z->j; + if (ends(z, "\02" "at")) setto(z, "\03" "ate"); else + if (ends(z, "\02" "bl")) setto(z, "\03" "ble"); else + if (ends(z, "\02" "iz")) setto(z, "\03" "ize"); else + if (doublec(z, z->k)) + { z->k--; + { int ch = b[z->k]; + if (ch == 'l' || ch == 's' || ch == 'z') z->k++; + } + } + else if (m(z) == 1 && cvc(z, z->k)) setto(z, "\01" "e"); + } +} + +/* step1c(z) turns terminal y to i when there is another vowel in the stem. */ + +static void step1c(struct stemmer * z) +{ + if (ends(z, "\01" "y") && vowelinstem(z)) z->b[z->k] = 'i'; +} + + +/* step2(z) maps double suffices to single ones. so -ization ( = -ize plus + -ation) maps to -ize etc. note that the string before the suffix must give + m(z) > 0. */ + +static void step2(struct stemmer * z) { switch (z->b[z->k-1]) +{ + case 'a': if (ends(z, "\07" "ational")) { r(z, "\03" "ate"); break; } + if (ends(z, "\06" "tional")) { r(z, "\04" "tion"); break; } + break; + case 'c': if (ends(z, "\04" "enci")) { r(z, "\04" "ence"); break; } + if (ends(z, "\04" "anci")) { r(z, "\04" "ance"); break; } + break; + case 'e': if (ends(z, "\04" "izer")) { r(z, "\03" "ize"); break; } + break; + case 'l': if (ends(z, "\03" "bli")) { r(z, "\03" "ble"); break; } /*-DEPARTURE-*/ + + /* To match the published algorithm, replace this line with + case 'l': if (ends(z, "\04" "abli")) { r(z, "\04" "able"); break; } */ + + if (ends(z, "\04" "alli")) { r(z, "\02" "al"); break; } + if (ends(z, "\05" "entli")) { r(z, "\03" "ent"); break; } + if (ends(z, "\03" "eli")) { r(z, "\01" "e"); break; } + if (ends(z, "\05" "ousli")) { r(z, "\03" "ous"); break; } + break; + case 'o': if (ends(z, "\07" "ization")) { r(z, "\03" "ize"); break; } + if (ends(z, "\05" "ation")) { r(z, "\03" "ate"); break; } + if (ends(z, "\04" "ator")) { r(z, "\03" "ate"); break; } + break; + case 's': if (ends(z, "\05" "alism")) { r(z, "\02" "al"); break; } + if (ends(z, "\07" "iveness")) { r(z, "\03" "ive"); break; } + if (ends(z, "\07" "fulness")) { r(z, "\03" "ful"); break; } + if (ends(z, "\07" "ousness")) { r(z, "\03" "ous"); break; } + break; + case 't': if (ends(z, "\05" "aliti")) { r(z, "\02" "al"); break; } + if (ends(z, "\05" "iviti")) { r(z, "\03" "ive"); break; } + if (ends(z, "\06" "biliti")) { r(z, "\03" "ble"); break; } + break; + case 'g': if (ends(z, "\04" "logi")) { r(z, "\03" "log"); break; } /*-DEPARTURE-*/ + + /* To match the published algorithm, delete this line */ + +} } + +/* step3(z) deals with -ic-, -full, -ness etc. similar strategy to step2. */ + +static void step3(struct stemmer * z) { switch (z->b[z->k]) +{ + case 'e': if (ends(z, "\05" "icate")) { r(z, "\02" "ic"); break; } + if (ends(z, "\05" "ative")) { r(z, "\00" ""); break; } + if (ends(z, "\05" "alize")) { r(z, "\02" "al"); break; } + break; + case 'i': if (ends(z, "\05" "iciti")) { r(z, "\02" "ic"); break; } + break; + case 'l': if (ends(z, "\04" "ical")) { r(z, "\02" "ic"); break; } + if (ends(z, "\03" "ful")) { r(z, "\00" ""); break; } + break; + case 's': if (ends(z, "\04" "ness")) { r(z, "\00" ""); break; } + break; +} } + +/* step4(z) takes off -ant, -ence etc., in context <c>vcvc<v>. */ + +static void step4(struct stemmer * z) +{ switch (z->b[z->k-1]) + { case 'a': if (ends(z, "\02" "al")) break; return; + case 'c': if (ends(z, "\04" "ance")) break; + if (ends(z, "\04" "ence")) break; return; + case 'e': if (ends(z, "\02" "er")) break; return; + case 'i': if (ends(z, "\02" "ic")) break; return; + case 'l': if (ends(z, "\04" "able")) break; + if (ends(z, "\04" "ible")) break; return; + case 'n': if (ends(z, "\03" "ant")) break; + if (ends(z, "\05" "ement")) break; + if (ends(z, "\04" "ment")) break; + if (ends(z, "\03" "ent")) break; return; + case 'o': if (ends(z, "\03" "ion") && z->j >= 0 && (z->b[z->j] == 's' || z->b[z->j] == 't')) break; + if (ends(z, "\02" "ou")) break; return; + /* takes care of -ous */ + case 's': if (ends(z, "\03" "ism")) break; return; + case 't': if (ends(z, "\03" "ate")) break; + if (ends(z, "\03" "iti")) break; return; + case 'u': if (ends(z, "\03" "ous")) break; return; + case 'v': if (ends(z, "\03" "ive")) break; return; + case 'z': if (ends(z, "\03" "ize")) break; return; + default: return; + } + if (m(z) > 1) z->k = z->j; +} + +/* step5(z) removes a final -e if m(z) > 1, and changes -ll to -l if + m(z) > 1. */ + +static void step5(struct stemmer * z) +{ + char * b = z->b; + z->j = z->k; + if (b[z->k] == 'e') + { int a = m(z); + if (a > 1 || a == 1 && !cvc(z, z->k - 1)) z->k--; + } + if (b[z->k] == 'l' && doublec(z, z->k) && m(z) > 1) z->k--; +} + +/* In stem(z, b, k), b is a char pointer, and the string to be stemmed is + from b[0] to b[k] inclusive. Possibly b[k+1] == '\0', but it is not + important. The stemmer adjusts the characters b[0] ... b[k] and returns + the new end-point of the string, k'. Stemming never increases word + length, so 0 <= k' <= k. +*/ + +extern int stem(struct stemmer * z, char * b, int k) +{ + if (k <= 1) return k; /*-DEPARTURE-*/ + z->b = b; z->k = k; /* copy the parameters into z */ + + /* With this line, strings of length 1 or 2 don't go through the + stemming process, although no mention is made of this in the + published algorithm. Remove the line to match the published + algorithm. */ + + step1ab(z); + if (z->k > 0) { + step1c(z); step2(z); step3(z); step4(z); step5(z); + } + return z->k; +} + +/*--------------------stemmer definition ends here------------------------*/ + +#include <stdio.h> +#include <stdlib.h> /* for malloc, free */ +#include <ctype.h> /* for isupper, islower, tolower */ + +static char * s; /* buffer for words tobe stemmed */ + +#define INC 50 /* size units in which s is increased */ +static int i_max = INC; /* maximum offset in s */ + +#define LETTER(ch) (isupper(ch) || islower(ch)) + +void stemfile(struct stemmer * z, FILE * f) +{ while(TRUE) + { int ch = getc(f); + if (ch == EOF) return; + if (LETTER(ch)) + { int i = 0; + while(TRUE) + { if (i == i_max) + { i_max += INC; + s = realloc(s, i_max + 1); + } + ch = tolower(ch); /* forces lower case */ + + s[i] = ch; i++; + ch = getc(f); + if (!LETTER(ch)) { ungetc(ch,f); break; } + } + s[stem(z, s, i - 1) + 1] = 0; + /* the previous line calls the stemmer and uses its result to + zero-terminate the string in s */ + printf("%s",s); + } + else putchar(ch); + } +} + +/* +int main(int argc, char * argv[]) +{ int i; + + struct stemmer * z = create_stemmer(); + + s = (char *) malloc(i_max + 1); + for (i = 1; i < argc; i++) + { FILE * f = fopen(argv[i],"r"); + if (f == 0) { fprintf(stderr,"File %s not found\n",argv[i]); exit(1); } + stemfile(z, f); + } + free(s); + + free_stemmer(z); + + return 0; +} +*/
Change 1 of 1 Show Entire File query.c Stacked
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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+#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include "kak/klist.h" +#include "post.h" +#include "term.h" +#include "query.h" + +Query *newquery(char *id) +{ + Query *q; + q = (Query *)malloc(sizeof(Query)); + q->id = strdup(id); + q->n_term = 0; + q->n_uterm = 0; + q->tlist = NULL; + return q; +} +void freequery(void *data) +{ + if (data == NULL) + return; + free(((Query *)data)->id); + freelist(((Query *)data)->tlist, freepost); + free(data); +} + +int cmpquery(void *d1, void *d2) +{ + return strcmp(((Query *)d1)->id, ((Query *)d2)->id); +} + +unsigned hashquery(void *data, unsigned hsize) +{ + static unsigned MULTIPLIER = 31; + unsigned h; + h = 0; + for (char *p = ((Post *)data)->id; *p != '\0'; p++) + h = MULTIPLIER * h + *p; + return h % hsize; +} + +void fprintquery(FILE *stream, void *data) +{ + Query *q; + q = (Query *)data; + fprintf(stream, " %s:%u:%u", q->id, q->n_term, q->n_uterm); + for (Node *np = q->tlist; np != NULL; np = np->next) + fprintpost(stream, np->data); +}
Change 1 of 1 Show Entire File query.h Stacked
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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+typedef struct Query Query; + +struct Query { + char *id; + uint32_t n_term; + uint32_t n_uterm; + Node *tlist; +}; + +Query *newquery(char*); +void freequery(void*); +int cmpquery(void*, void*); +unsigned hashquery(void*, unsigned); +void fprintquery(FILE*, void*);
Change 1 of 1 Show Entire File stemmer.h Stacked
 
 
 
 
 
 
 
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+typedef struct stemmer Stemmer; + +Stemmer *create_stemmer(void); +void free_stemmer(Stemmer*); +int stem(Stemmer*, char*, int);