liquid_feedback_core
view lf_update_suggestion_order.c @ 413:e024c50cfe3d
Added tag v3.0.0 for changeset 399dc1a86398
| author | jbe |
|---|---|
| date | Fri Jan 31 12:46:17 2014 +0100 (2014-01-31) |
| parents | eda636259846 |
| children | 82387194519b |
line source
1 #include <stdlib.h>
2 #include <stdio.h>
3 #include <string.h>
4 #include <libpq-fe.h>
5 #include <search.h>
7 static int logging = 0;
9 static char *escapeLiteral(PGconn *conn, const char *str, size_t len) {
10 // provides compatibility for PostgreSQL versions prior 9.0
11 // in future: return PQescapeLiteral(conn, str, len);
12 char *res;
13 size_t res_len;
14 res = malloc(2*len+3);
15 if (!res) return NULL;
16 res[0] = '\'';
17 res_len = PQescapeStringConn(conn, res+1, str, len, NULL);
18 res[res_len+1] = '\'';
19 res[res_len+2] = 0;
20 return res;
21 }
23 static void freemem(void *ptr) {
24 // to be used for "escapeLiteral" function
25 // provides compatibility for PostgreSQL versions prior 9.0
26 // in future: PQfreemem(ptr);
27 free(ptr);
28 }
30 // column numbers when querying "individual_suggestion_ranking" view in function main():
31 #define COL_MEMBER_ID 0
32 #define COL_WEIGHT 1
33 #define COL_PREFERENCE 2
34 #define COL_SUGGESTION_ID 3
36 // data structure for a candidate (in this case a suggestion) to the proportional runoff system:
37 struct candidate {
38 char *key; // identifier of the candidate, which is the "suggestion_id" string
39 double score_per_step; // added score per step
40 double score; // current score of candidate; a score of 1.0 is needed to survive a round
41 int seat; // equals 0 for unseated candidates, or contains rank number
42 };
44 // compare two integers stored as strings (invocation like strcmp):
45 static int compare_id(char *id1, char *id2) {
46 int ldiff;
47 ldiff = strlen(id1) - strlen(id2);
48 if (ldiff) return ldiff;
49 else return strcmp(id1, id2);
50 }
52 // compare two candidates by their key (invocation like strcmp):
53 static int compare_candidate(struct candidate *c1, struct candidate *c2) {
54 return compare_id(c1->key, c2->key);
55 }
57 // candidates are stored as global variables due to the constrained twalk() interface:
58 static int candidate_count;
59 static struct candidate *candidates;
61 // function to be passed to twalk() to store candidates ordered in candidates[] array:
62 static void register_candidate(char **candidate_key, VISIT visit, int level) {
63 if (visit == postorder || visit == leaf) {
64 struct candidate *candidate;
65 candidate = candidates + (candidate_count++);
66 candidate->key = *candidate_key;
67 candidate->seat = 0;
68 if (logging) printf("Candidate #%i is suggestion #%s.\n", candidate_count, candidate->key);
69 }
70 }
72 // performs a binary search in candidates[] array to lookup a candidate by its key (which is the suggestion_id):
73 static struct candidate *candidate_by_key(char *candidate_key) {
74 struct candidate *candidate;
75 struct candidate compare;
76 compare.key = candidate_key;
77 candidate = bsearch(&compare, candidates, candidate_count, sizeof(struct candidate), (void *)compare_candidate);
78 if (!candidate) {
79 fprintf(stderr, "Candidate not found (should not happen).\n");
80 abort();
81 }
82 return candidate;
83 }
85 // section of a ballot with equally ranked candidates:
86 struct ballot_section {
87 int count;
88 struct candidate **candidates;
89 };
91 // ballot of the proportional runoff system:
92 struct ballot {
93 int weight; // if weight is greater than 1, then the ballot is counted multiple times
94 struct ballot_section sections[4]; // 4 sections, most preferred candidates first
95 };
97 // determine candidate, which is assigned the next seat (starting with the worst rank):
98 static struct candidate *loser(int round_number, struct ballot *ballots, int ballot_count) {
99 int i, j, k; // index variables for loops
100 int remaining; // remaining candidates to be seated
101 // reset scores of all candidates:
102 for (i=0; i<candidate_count; i++) {
103 candidates[i].score = 0.0;
104 }
105 // calculate remaining candidates to be seated:
106 remaining = candidate_count - round_number;
107 // repeat following loop, as long as there is more than one remaining candidate:
108 while (remaining > 1) {
109 if (logging) printf("There are %i remaining candidates.\n", remaining);
110 double scale; // factor to be later multiplied with score_per_step:
111 // reset score_per_step for all candidates:
112 for (i=0; i<candidate_count; i++) {
113 candidates[i].score_per_step = 0.0;
114 }
115 // calculate score_per_step for all candidates:
116 for (i=0; i<ballot_count; i++) {
117 for (j=0; j<4; j++) {
118 int matches = 0;
119 for (k=0; k<ballots[i].sections[j].count; k++) {
120 struct candidate *candidate;
121 candidate = ballots[i].sections[j].candidates[k];
122 if (candidate->score < 1.0 && !candidate->seat) matches++;
123 }
124 if (matches) {
125 double score_inc;
126 score_inc = (double)ballots[i].weight / (double)matches;
127 for (k=0; k<ballots[i].sections[j].count; k++) {
128 struct candidate *candidate;
129 candidate = ballots[i].sections[j].candidates[k];
130 if (candidate->score < 1.0 && !candidate->seat) {
131 candidate->score_per_step += score_inc;
132 }
133 }
134 break;
135 }
136 }
137 }
138 // calculate scale factor:
139 scale = (double)0.0; // 0.0 is used to indicate that there is no value yet
140 for (i=0; i<candidate_count; i++) {
141 double max_scale;
142 if (candidates[i].score_per_step > 0.0) {
143 max_scale = (1.0-candidates[i].score) / candidates[i].score_per_step;
144 if (scale == 0.0 || max_scale <= scale) {
145 scale = max_scale;
146 }
147 }
148 }
149 // add scale*score_per_step to each candidates score:
150 for (i=0; i<candidate_count; i++) {
151 int log_candidate = 0;
152 if (logging && candidates[i].score < 1.0 && !candidates[i].seat) log_candidate = 1;
153 if (log_candidate) printf("Score for suggestion #%s = %.4f+%.4f*%.4f", candidates[i].key, candidates[i].score, scale, candidates[i].score_per_step);
154 if (candidates[i].score_per_step > 0.0) {
155 double max_scale;
156 max_scale = (1.0-candidates[i].score) / candidates[i].score_per_step;
157 if (max_scale == scale) {
158 // score of 1.0 should be reached, so we set score directly to avoid floating point errors:
159 candidates[i].score = 1.0;
160 remaining--;
161 } else {
162 candidates[i].score += scale * candidates[i].score_per_step;
163 if (candidates[i].score >= 1.0) remaining--;
164 }
165 }
166 if (log_candidate) {
167 if (candidates[i].score >= 1.0) printf("=1\n");
168 else printf("=%.4f\n", candidates[i].score);
169 }
170 // when there is only one candidate remaining, then break inner (and thus outer) loop:
171 if (remaining <= 1) {
172 break;
173 }
174 }
175 }
176 // return remaining candidate:
177 for (i=0; i<candidate_count; i++) {
178 if (candidates[i].score < 1.0 && !candidates[i].seat) return candidates+i;
179 }
180 // if there is no remaining candidate, then something went wrong:
181 fprintf(stderr, "No remaining candidate (should not happen).");
182 abort();
183 }
185 // write results to database:
186 static int write_ranks(PGconn *db, char *escaped_initiative_id, int final) {
187 PGresult *res;
188 char *cmd;
189 int i;
190 if (final) {
191 if (asprintf(&cmd, "BEGIN; UPDATE \"initiative\" SET \"final_suggestion_order_calculated\" = TRUE WHERE \"id\" = %s; UPDATE \"suggestion\" SET \"proportional_order\" = NULL WHERE \"initiative_id\" = %s", escaped_initiative_id, escaped_initiative_id) < 0) {
192 fprintf(stderr, "Could not prepare query string in memory.\n");
193 abort();
194 }
195 } else {
196 if (asprintf(&cmd, "BEGIN; UPDATE \"suggestion\" SET \"proportional_order\" = NULL WHERE \"initiative_id\" = %s", escaped_initiative_id) < 0) {
197 fprintf(stderr, "Could not prepare query string in memory.\n");
198 abort();
199 }
200 }
201 res = PQexec(db, cmd);
202 free(cmd);
203 if (!res) {
204 fprintf(stderr, "Error in pqlib while sending SQL command to initiate suggestion update.\n");
205 return 1;
206 } else if (
207 PQresultStatus(res) != PGRES_COMMAND_OK &&
208 PQresultStatus(res) != PGRES_TUPLES_OK
209 ) {
210 fprintf(stderr, "Error while executing SQL command to initiate suggestion update:\n%s", PQresultErrorMessage(res));
211 PQclear(res);
212 return 1;
213 } else {
214 PQclear(res);
215 }
216 for (i=0; i<candidate_count; i++) {
217 char *escaped_suggestion_id;
218 escaped_suggestion_id = escapeLiteral(db, candidates[i].key, strlen(candidates[i].key));
219 if (!escaped_suggestion_id) {
220 fprintf(stderr, "Could not escape literal in memory.\n");
221 abort();
222 }
223 if (asprintf(&cmd, "UPDATE \"suggestion\" SET \"proportional_order\" = %i WHERE \"id\" = %s", candidates[i].seat, escaped_suggestion_id) < 0) {
224 fprintf(stderr, "Could not prepare query string in memory.\n");
225 abort();
226 }
227 freemem(escaped_suggestion_id);
228 res = PQexec(db, cmd);
229 free(cmd);
230 if (!res) {
231 fprintf(stderr, "Error in pqlib while sending SQL command to update suggestion order.\n");
232 } else if (
233 PQresultStatus(res) != PGRES_COMMAND_OK &&
234 PQresultStatus(res) != PGRES_TUPLES_OK
235 ) {
236 fprintf(stderr, "Error while executing SQL command to update suggestion order:\n%s", PQresultErrorMessage(res));
237 PQclear(res);
238 } else {
239 PQclear(res);
240 continue;
241 }
242 res = PQexec(db, "ROLLBACK");
243 if (res) PQclear(res);
244 return 1;
245 }
246 res = PQexec(db, "COMMIT");
247 if (!res) {
248 fprintf(stderr, "Error in pqlib while sending SQL command to commit transaction.\n");
249 return 1;
250 } else if (
251 PQresultStatus(res) != PGRES_COMMAND_OK &&
252 PQresultStatus(res) != PGRES_TUPLES_OK
253 ) {
254 fprintf(stderr, "Error while executing SQL command to commit transaction:\n%s", PQresultErrorMessage(res));
255 PQclear(res);
256 return 1;
257 } else {
258 PQclear(res);
259 return 0;
260 }
261 }
263 // calculate ordering of suggestions for an initiative and call write_ranks() to write it to database:
264 static int process_initiative(PGconn *db, PGresult *res, char *escaped_initiative_id, int final) {
265 int err; // variable to store an error condition (0 = success)
266 int ballot_count = 1; // number of ballots, must be initiatized to 1, due to loop below
267 struct ballot *ballots; // data structure containing the ballots
268 int i; // index variable for loops
269 // create candidates[] and ballots[] arrays:
270 {
271 void *candidate_tree = NULL; // temporary structure to create a sorted unique list of all candidate keys
272 int tuple_count; // number of tuples returned from the database
273 char *old_member_id = NULL; // old member_id to be able to detect a new ballot in loops
274 struct ballot *ballot; // pointer to current ballot
275 int candidates_in_sections[4] = {0, }; // number of candidates that have been placed in each section
276 // reset candidate count:
277 candidate_count = 0;
278 // determine number of tuples:
279 tuple_count = PQntuples(res);
280 // trivial case, when there are no tuples:
281 if (!tuple_count) {
282 if (final) {
283 if (logging) printf("No suggestions found, but marking initiative as finally calculated.\n");
284 err = write_ranks(db, escaped_initiative_id, final);
285 if (logging) printf("Done.\n");
286 return err;
287 } else {
288 if (logging) printf("Nothing to do.\n");
289 return 0;
290 }
291 }
292 // calculate ballot_count and generate set of candidate keys (suggestion_id is used as key):
293 for (i=0; i<tuple_count; i++) {
294 char *member_id, *suggestion_id;
295 member_id = PQgetvalue(res, i, COL_MEMBER_ID);
296 suggestion_id = PQgetvalue(res, i, COL_SUGGESTION_ID);
297 if (!candidate_tree || !tfind(suggestion_id, &candidate_tree, (void *)compare_id)) {
298 candidate_count++;
299 if (!tsearch(suggestion_id, &candidate_tree, (void *)compare_id)) {
300 fprintf(stderr, "Insufficient memory while inserting into candidate tree.\n");
301 abort();
302 }
303 }
304 if (old_member_id && strcmp(old_member_id, member_id)) ballot_count++;
305 old_member_id = member_id;
306 }
307 // allocate memory for candidates[] array:
308 candidates = malloc(candidate_count * sizeof(struct candidate));
309 if (!candidates) {
310 fprintf(stderr, "Insufficient memory while creating candidate list.\n");
311 abort();
312 }
313 // transform tree of candidate keys into sorted array:
314 candidate_count = 0; // needed by register_candidate()
315 twalk(candidate_tree, (void *)register_candidate);
316 // free memory of tree structure (tdestroy() is not available on all platforms):
317 while (candidate_tree) tdelete(*(void **)candidate_tree, &candidate_tree, (void *)compare_id);
318 // allocate memory for ballots[] array:
319 ballots = calloc(ballot_count, sizeof(struct ballot));
320 if (!ballots) {
321 fprintf(stderr, "Insufficient memory while creating ballot list.\n");
322 abort();
323 }
324 // set ballot weights, determine ballot section sizes, and verify preference values:
325 ballot = ballots;
326 old_member_id = NULL;
327 for (i=0; i<tuple_count; i++) {
328 char *member_id;
329 int weight, preference;
330 member_id = PQgetvalue(res, i, COL_MEMBER_ID);
331 weight = (int)strtol(PQgetvalue(res, i, COL_WEIGHT), (char **)NULL, 10);
332 if (weight <= 0) {
333 fprintf(stderr, "Unexpected weight value.\n");
334 free(ballots);
335 free(candidates);
336 return 1;
337 }
338 preference = (int)strtol(PQgetvalue(res, i, COL_PREFERENCE), (char **)NULL, 10);
339 if (preference < 1 || preference > 4) {
340 fprintf(stderr, "Unexpected preference value.\n");
341 free(ballots);
342 free(candidates);
343 return 1;
344 }
345 preference--;
346 if (old_member_id && strcmp(old_member_id, member_id)) ballot++;
347 ballot->weight = weight;
348 ballot->sections[preference].count++;
349 old_member_id = member_id;
350 }
351 // allocate memory for ballot sections:
352 for (i=0; i<ballot_count; i++) {
353 int j;
354 for (j=0; j<4; j++) {
355 if (ballots[i].sections[j].count) {
356 ballots[i].sections[j].candidates = malloc(ballots[i].sections[j].count * sizeof(struct candidate *));
357 if (!ballots[i].sections[j].candidates) {
358 fprintf(stderr, "Insufficient memory while creating ballot section.\n");
359 abort();
360 }
361 }
362 }
363 }
364 // fill ballot sections with candidate references:
365 old_member_id = NULL;
366 ballot = ballots;
367 for (i=0; i<tuple_count; i++) {
368 char *member_id, *suggestion_id;
369 int preference;
370 member_id = PQgetvalue(res, i, COL_MEMBER_ID);
371 suggestion_id = PQgetvalue(res, i, COL_SUGGESTION_ID);
372 preference = (int)strtol(PQgetvalue(res, i, COL_PREFERENCE), (char **)NULL, 10);
373 preference--;
374 if (old_member_id && strcmp(old_member_id, member_id)) {
375 ballot++;
376 candidates_in_sections[0] = 0;
377 candidates_in_sections[1] = 0;
378 candidates_in_sections[2] = 0;
379 candidates_in_sections[3] = 0;
380 }
381 ballot->sections[preference].candidates[candidates_in_sections[preference]++] = candidate_by_key(suggestion_id);
382 old_member_id = member_id;
383 }
384 // print ballots, if logging is enabled:
385 if (logging) {
386 for (i=0; i<ballot_count; i++) {
387 int j;
388 for (j=0; j<4; j++) {
389 int k;
390 printf("Ballot #%i, ", i+1);
391 if (j==0) printf("1st");
392 if (j==1) printf("2nd");
393 if (j==2) printf("3rd");
394 if (j==3) printf("4th");
395 printf(" preference: ");
396 for (k=0; k<ballots[i].sections[j].count; k++) {
397 if (!k) printf("suggestions ");
398 else printf(", ");
399 printf("#%s", ballots[i].sections[j].candidates[k]->key);
400 }
401 if (!k) printf("empty");
402 printf(".\n");
403 }
404 }
405 }
406 }
408 // calculate ranks based on constructed data structures:
409 for (i=0; i<candidate_count; i++) {
410 struct candidate *candidate = loser(i, ballots, ballot_count);
411 candidate->seat = candidate_count - i;
412 if (logging) printf("Assigning rank #%i to suggestion #%s.\n", candidate_count-i, candidate->key);
413 }
415 // free ballots[] array:
416 for (i=0; i<ballot_count; i++) {
417 int j;
418 for (j=0; j<4; j++) {
419 if (ballots[i].sections[j].count) {
420 free(ballots[i].sections[j].candidates);
421 }
422 }
423 }
424 free(ballots);
426 // write results to database:
427 if (final) {
428 if (logging) printf("Writing final ranks to database.\n");
429 } else {
430 if (logging) printf("Writing ranks to database.\n");
431 }
432 err = write_ranks(db, escaped_initiative_id, final);
433 if (logging) printf("Done.\n");
435 // free candidates[] array:
436 free(candidates);
438 // return error code of write_ranks() call
439 return err;
440 }
442 int main(int argc, char **argv) {
444 // variable declarations:
445 int err = 0;
446 int i, count;
447 char *conninfo;
448 PGconn *db;
449 PGresult *res;
451 // parse command line:
452 if (argc == 0) return 1;
453 if (argc == 1 || !strcmp(argv[1], "-h") || !strcmp(argv[1], "--help")) {
454 FILE *out;
455 out = argc == 1 ? stderr : stdout;
456 fprintf(out, "\n");
457 fprintf(out, "Usage: %s [-v|--verbose] <conninfo>\n", argv[0]);
458 fprintf(out, "\n");
459 fprintf(out, "<conninfo> is specified by PostgreSQL's libpq,\n");
460 fprintf(out, "see http://www.postgresql.org/docs/9.1/static/libpq-connect.html\n");
461 fprintf(out, "\n");
462 fprintf(out, "Example: %s dbname=liquid_feedback\n", argv[0]);
463 fprintf(out, "\n");
464 return argc == 1 ? 1 : 0;
465 }
466 {
467 size_t len = 0;
468 int argb = 1;
469 if (
470 argc >= 2 &&
471 (!strcmp(argv[1], "-v") || !strcmp(argv[1], "--verbose"))
472 ) {
473 argb = 2;
474 logging = 1;
475 }
476 for (i=argb; i<argc; i++) len += strlen(argv[i]) + 1;
477 conninfo = malloc(len * sizeof(char));
478 if (!conninfo) {
479 fprintf(stderr, "Error: Could not allocate memory for conninfo string.\n");
480 abort();
481 }
482 conninfo[0] = 0;
483 for (i=argb; i<argc; i++) {
484 if (i>argb) strcat(conninfo, " ");
485 strcat(conninfo, argv[i]);
486 }
487 }
489 // connect to database:
490 db = PQconnectdb(conninfo);
491 if (!db) {
492 fprintf(stderr, "Error: Could not create database handle.\n");
493 return 1;
494 }
495 if (PQstatus(db) != CONNECTION_OK) {
496 fprintf(stderr, "Could not open connection:\n%s", PQerrorMessage(db));
497 return 1;
498 }
500 // check initiatives:
501 res = PQexec(db, "SELECT \"initiative_id\", \"final\" FROM \"initiative_suggestion_order_calculation\"");
502 if (!res) {
503 fprintf(stderr, "Error in pqlib while sending SQL command selecting initiatives to process.\n");
504 err = 1;
505 } else if (PQresultStatus(res) != PGRES_TUPLES_OK) {
506 fprintf(stderr, "Error while executing SQL command selecting initiatives to process:\n%s", PQresultErrorMessage(res));
507 err = 1;
508 PQclear(res);
509 } else if (PQnfields(res) < 2) {
510 fprintf(stderr, "Too few columns returned by SQL command selecting initiatives to process.\n");
511 err = 1;
512 PQclear(res);
513 } else {
514 count = PQntuples(res);
515 if (logging) printf("Number of initiatives to process: %i\n", count);
516 for (i=0; i<count; i++) {
517 char *initiative_id, *escaped_initiative_id;
518 int final;
519 char *cmd;
520 PGresult *res2;
521 initiative_id = PQgetvalue(res, i, 0);
522 final = (PQgetvalue(res, i, 1)[0] == 't') ? 1 : 0;
523 if (logging) printf("Processing initiative #%s:\n", initiative_id);
524 escaped_initiative_id = escapeLiteral(db, initiative_id, strlen(initiative_id));
525 if (!escaped_initiative_id) {
526 fprintf(stderr, "Could not escape literal in memory.\n");
527 abort();
528 }
529 if (asprintf(&cmd, "SELECT \"member_id\", \"weight\", \"preference\", \"suggestion_id\" FROM \"individual_suggestion_ranking\" WHERE \"initiative_id\" = %s ORDER BY \"member_id\", \"preference\"", escaped_initiative_id) < 0) {
530 fprintf(stderr, "Could not prepare query string in memory.\n");
531 abort();
532 }
533 res2 = PQexec(db, cmd);
534 free(cmd);
535 if (!res2) {
536 fprintf(stderr, "Error in pqlib while sending SQL command selecting individual suggestion rankings.\n");
537 err = 1;
538 } else if (PQresultStatus(res2) != PGRES_TUPLES_OK) {
539 fprintf(stderr, "Error while executing SQL command selecting individual suggestion rankings:\n%s", PQresultErrorMessage(res));
540 err = 1;
541 PQclear(res2);
542 } else if (PQnfields(res2) < 4) {
543 fprintf(stderr, "Too few columns returned by SQL command selecting individual suggestion rankings.\n");
544 err = 1;
545 PQclear(res2);
546 } else {
547 if (process_initiative(db, res2, escaped_initiative_id, final)) err = 1;
548 PQclear(res2);
549 }
550 freemem(escaped_initiative_id);
551 }
552 PQclear(res);
553 }
555 // cleanup and exit:
556 PQfinish(db);
557 if (!err) {
558 if (logging) printf("Successfully terminated.\n");
559 } else {
560 fprintf(stderr, "Exiting with error code %i.\n", err);
561 }
562 return err;
564 }