Line data Source code
1 : /*------------------------------------------------------------------------
2 : *
3 : * geqo_erx.c
4 : * edge recombination crossover [ER]
5 : *
6 : * src/backend/optimizer/geqo/geqo_erx.c
7 : *
8 : *-------------------------------------------------------------------------
9 : */
10 :
11 : /*
12 : * contributed by:
13 : * =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
14 : * * Martin Utesch * Institute of Automatic Control *
15 : * = = University of Mining and Technology =
16 : * * utesch@aut.tu-freiberg.de * Freiberg, Germany *
17 : * =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
18 : */
19 :
20 : /* the edge recombination algorithm is adopted from Genitor : */
21 : /*************************************************************/
22 : /* */
23 : /* Copyright (c) 1990 */
24 : /* Darrell L. Whitley */
25 : /* Computer Science Department */
26 : /* Colorado State University */
27 : /* */
28 : /* Permission is hereby granted to copy all or any part of */
29 : /* this program for free distribution. The author's name */
30 : /* and this copyright notice must be included in any copy. */
31 : /* */
32 : /*************************************************************/
33 :
34 :
35 : #include "postgres.h"
36 : #include "optimizer/geqo.h"
37 :
38 : #if defined(ERX)
39 :
40 : #include "optimizer/geqo_random.h"
41 : #include "optimizer/geqo_recombination.h"
42 :
43 : static int gimme_edge(PlannerInfo *root, Gene gene1, Gene gene2, Edge *edge_table);
44 : static void remove_gene(PlannerInfo *root, Gene gene, Edge edge, Edge *edge_table);
45 : static Gene gimme_gene(PlannerInfo *root, Edge edge, Edge *edge_table);
46 :
47 : static Gene edge_failure(PlannerInfo *root, Gene *gene, int index, Edge *edge_table, int num_gene);
48 :
49 :
50 : /*
51 : * alloc_edge_table
52 : *
53 : * allocate memory for edge table
54 : *
55 : */
56 :
57 : Edge *
58 35 : alloc_edge_table(PlannerInfo *root, int num_gene)
59 : {
60 : Edge *edge_table;
61 :
62 : /*
63 : * palloc one extra location so that nodes numbered 1..n can be indexed
64 : * directly; 0 will not be used
65 : */
66 :
67 35 : edge_table = palloc_array(Edge, num_gene + 1);
68 :
69 35 : return edge_table;
70 : }
71 :
72 : /*
73 : * free_edge_table
74 : *
75 : * deallocate memory of edge table
76 : *
77 : */
78 : void
79 35 : free_edge_table(PlannerInfo *root, Edge *edge_table)
80 : {
81 35 : pfree(edge_table);
82 35 : }
83 :
84 : /*
85 : * gimme_edge_table
86 : *
87 : * fills a data structure which represents the set of explicit
88 : * edges between points in the (2) input genes
89 : *
90 : * assumes circular tours and bidirectional edges
91 : *
92 : * gimme_edge() will set "shared" edges to negative values
93 : *
94 : * returns average number edges/city in range 2.0 - 4.0
95 : * where 2.0=homogeneous; 4.0=diverse
96 : *
97 : */
98 : float
99 1820 : gimme_edge_table(PlannerInfo *root, Gene *tour1, Gene *tour2,
100 : int num_gene, Edge *edge_table)
101 : {
102 : int i,
103 : index1,
104 : index2;
105 : int edge_total; /* total number of unique edges in two genes */
106 :
107 : /* at first clear the edge table's old data */
108 6420 : for (i = 1; i <= num_gene; i++)
109 : {
110 4600 : edge_table[i].total_edges = 0;
111 4600 : edge_table[i].unused_edges = 0;
112 : }
113 :
114 : /* fill edge table with new data */
115 :
116 1820 : edge_total = 0;
117 :
118 6420 : for (index1 = 0; index1 < num_gene; index1++)
119 : {
120 : /*
121 : * presume the tour is circular, i.e. 1->2, 2->3, 3->1 this operation
122 : * maps n back to 1
123 : */
124 :
125 4600 : index2 = (index1 + 1) % num_gene;
126 :
127 : /*
128 : * edges are bidirectional, i.e. 1->2 is same as 2->1 call gimme_edge
129 : * twice per edge
130 : */
131 :
132 4600 : edge_total += gimme_edge(root, tour1[index1], tour1[index2], edge_table);
133 4600 : gimme_edge(root, tour1[index2], tour1[index1], edge_table);
134 :
135 4600 : edge_total += gimme_edge(root, tour2[index1], tour2[index2], edge_table);
136 4600 : gimme_edge(root, tour2[index2], tour2[index1], edge_table);
137 : }
138 :
139 : /* return average number of edges per index */
140 1820 : return ((float) (edge_total * 2) / (float) num_gene);
141 : }
142 :
143 : /*
144 : * gimme_edge
145 : *
146 : * registers edge from city1 to city2 in input edge table
147 : *
148 : * no assumptions about directionality are made;
149 : * therefore it is up to the calling routine to
150 : * call gimme_edge twice to make a bi-directional edge
151 : * between city1 and city2;
152 : * uni-directional edges are possible as well (just call gimme_edge
153 : * once with the direction from city1 to city2)
154 : *
155 : * returns 1 if edge was not already registered and was just added;
156 : * 0 if edge was already registered and edge_table is unchanged
157 : */
158 : static int
159 18400 : gimme_edge(PlannerInfo *root, Gene gene1, Gene gene2, Edge *edge_table)
160 : {
161 : int i;
162 : int edges;
163 18400 : int city1 = (int) gene1;
164 18400 : int city2 = (int) gene2;
165 :
166 :
167 : /* check whether edge city1->city2 already exists */
168 18400 : edges = edge_table[city1].total_edges;
169 :
170 23265 : for (i = 0; i < edges; i++)
171 : {
172 16095 : if ((Gene) abs(edge_table[city1].edge_list[i]) == city2)
173 : {
174 :
175 : /* mark shared edges as negative */
176 11230 : edge_table[city1].edge_list[i] = 0 - city2;
177 :
178 11230 : return 0;
179 : }
180 : }
181 :
182 : /* add city1->city2; */
183 7170 : edge_table[city1].edge_list[edges] = city2;
184 :
185 : /* increment the number of edges from city1 */
186 7170 : edge_table[city1].total_edges++;
187 7170 : edge_table[city1].unused_edges++;
188 :
189 7170 : return 1;
190 : }
191 :
192 : /*
193 : * gimme_tour
194 : *
195 : * creates a new tour using edges from the edge table.
196 : * priority is given to "shared" edges (i.e. edges which
197 : * all parent genes possess and are marked as negative
198 : * in the edge table.)
199 : *
200 : */
201 : int
202 1820 : gimme_tour(PlannerInfo *root, Edge *edge_table, Gene *new_gene, int num_gene)
203 : {
204 : int i;
205 1820 : int edge_failures = 0;
206 :
207 : /* choose int between 1 and num_gene */
208 1820 : new_gene[0] = (Gene) geqo_randint(root, num_gene, 1);
209 :
210 4600 : for (i = 1; i < num_gene; i++)
211 : {
212 : /*
213 : * as each point is entered into the tour, remove it from the edge
214 : * table
215 : */
216 :
217 2780 : remove_gene(root, new_gene[i - 1], edge_table[(int) new_gene[i - 1]], edge_table);
218 :
219 : /* find destination for the newly entered point */
220 :
221 2780 : if (edge_table[new_gene[i - 1]].unused_edges > 0)
222 2780 : new_gene[i] = gimme_gene(root, edge_table[(int) new_gene[i - 1]], edge_table);
223 :
224 : else
225 : { /* cope with fault */
226 0 : edge_failures++;
227 :
228 0 : new_gene[i] = edge_failure(root, new_gene, i - 1, edge_table, num_gene);
229 : }
230 :
231 : /* mark this node as incorporated */
232 2780 : edge_table[(int) new_gene[i - 1]].unused_edges = -1;
233 : } /* for (i=1; i<num_gene; i++) */
234 :
235 1820 : return edge_failures;
236 : }
237 :
238 : /*
239 : * remove_gene
240 : *
241 : * removes input gene from edge_table.
242 : * input edge is used
243 : * to identify deletion locations within edge table.
244 : *
245 : */
246 : static void
247 2780 : remove_gene(PlannerInfo *root, Gene gene, Edge edge, Edge *edge_table)
248 : {
249 : int i,
250 : j;
251 : int possess_edge;
252 : int genes_remaining;
253 :
254 : /*
255 : * do for every gene known to have an edge to input gene (i.e. in
256 : * edge_list for input edge)
257 : */
258 :
259 6365 : for (i = 0; i < edge.unused_edges; i++)
260 : {
261 3585 : possess_edge = abs(edge.edge_list[i]);
262 3585 : genes_remaining = edge_table[possess_edge].unused_edges;
263 :
264 : /* find the input gene in all edge_lists and delete it */
265 4805 : for (j = 0; j < genes_remaining; j++)
266 : {
267 :
268 4805 : if ((Gene) abs(edge_table[possess_edge].edge_list[j]) == gene)
269 : {
270 :
271 3585 : edge_table[possess_edge].unused_edges--;
272 :
273 3585 : edge_table[possess_edge].edge_list[j] =
274 3585 : edge_table[possess_edge].edge_list[genes_remaining - 1];
275 :
276 3585 : break;
277 : }
278 : }
279 : }
280 2780 : }
281 :
282 : /*
283 : * gimme_gene
284 : *
285 : * priority is given to "shared" edges
286 : * (i.e. edges which both genes possess)
287 : *
288 : */
289 : static Gene
290 2780 : gimme_gene(PlannerInfo *root, Edge edge, Edge *edge_table)
291 : {
292 : int i;
293 : Gene friend;
294 : int minimum_edges;
295 2780 : int minimum_count = -1;
296 : int rand_decision;
297 :
298 : /*
299 : * no point has edges to more than 4 other points thus, this contrived
300 : * minimum will be replaced
301 : */
302 :
303 2780 : minimum_edges = 5;
304 :
305 : /* consider candidate destination points in edge list */
306 :
307 3535 : for (i = 0; i < edge.unused_edges; i++)
308 : {
309 3210 : friend = (Gene) edge.edge_list[i];
310 :
311 : /*
312 : * give priority to shared edges that are negative; so return 'em
313 : */
314 :
315 : /*
316 : * negative values are caught here so we need not worry about
317 : * converting to absolute values
318 : */
319 3210 : if (friend < 0)
320 2455 : return (Gene) abs(friend);
321 :
322 :
323 : /*
324 : * give priority to candidates with fewest remaining unused edges;
325 : * find out what the minimum number of unused edges is
326 : * (minimum_edges); if there is more than one candidate with the
327 : * minimum number of unused edges keep count of this number
328 : * (minimum_count);
329 : */
330 :
331 : /*
332 : * The test for minimum_count can probably be removed at some point
333 : * but comments should probably indicate exactly why it is guaranteed
334 : * that the test will always succeed the first time around. If it can
335 : * fail then the code is in error
336 : */
337 :
338 :
339 755 : if (edge_table[(int) friend].unused_edges < minimum_edges)
340 : {
341 415 : minimum_edges = edge_table[(int) friend].unused_edges;
342 415 : minimum_count = 1;
343 : }
344 340 : else if (minimum_count == -1)
345 0 : elog(ERROR, "minimum_count not set");
346 340 : else if (edge_table[(int) friend].unused_edges == minimum_edges)
347 340 : minimum_count++;
348 : } /* for (i=0; i<edge.unused_edges; i++) */
349 :
350 :
351 : /* random decision of the possible candidates to use */
352 325 : rand_decision = geqo_randint(root, minimum_count - 1, 0);
353 :
354 :
355 475 : for (i = 0; i < edge.unused_edges; i++)
356 : {
357 475 : friend = (Gene) edge.edge_list[i];
358 :
359 : /* return the chosen candidate point */
360 475 : if (edge_table[(int) friend].unused_edges == minimum_edges)
361 : {
362 475 : minimum_count--;
363 :
364 475 : if (minimum_count == rand_decision)
365 325 : return friend;
366 : }
367 : }
368 :
369 : /* ... should never be reached */
370 0 : elog(ERROR, "neither shared nor minimum number nor random edge found");
371 : return 0; /* to keep the compiler quiet */
372 : }
373 :
374 : /*
375 : * edge_failure
376 : *
377 : * routine for handling edge failure
378 : *
379 : */
380 : static Gene
381 0 : edge_failure(PlannerInfo *root, Gene *gene, int index, Edge *edge_table, int num_gene)
382 : {
383 : int i;
384 0 : Gene fail_gene = gene[index];
385 0 : int remaining_edges = 0;
386 0 : int four_count = 0;
387 : int rand_decision;
388 :
389 :
390 : /*
391 : * how many edges remain? how many gene with four total (initial) edges
392 : * remain?
393 : */
394 :
395 0 : for (i = 1; i <= num_gene; i++)
396 : {
397 0 : if ((edge_table[i].unused_edges != -1) && (i != (int) fail_gene))
398 : {
399 0 : remaining_edges++;
400 :
401 0 : if (edge_table[i].total_edges == 4)
402 0 : four_count++;
403 : }
404 : }
405 :
406 : /*
407 : * random decision of the gene with remaining edges and whose total_edges
408 : * == 4
409 : */
410 :
411 0 : if (four_count != 0)
412 : {
413 :
414 0 : rand_decision = geqo_randint(root, four_count - 1, 0);
415 :
416 0 : for (i = 1; i <= num_gene; i++)
417 : {
418 :
419 0 : if ((Gene) i != fail_gene &&
420 0 : edge_table[i].unused_edges != -1 &&
421 0 : edge_table[i].total_edges == 4)
422 : {
423 :
424 0 : four_count--;
425 :
426 0 : if (rand_decision == four_count)
427 0 : return (Gene) i;
428 : }
429 : }
430 :
431 0 : elog(LOG, "no edge found via random decision and total_edges == 4");
432 : }
433 0 : else if (remaining_edges != 0)
434 : {
435 : /* random decision of the gene with remaining edges */
436 0 : rand_decision = geqo_randint(root, remaining_edges - 1, 0);
437 :
438 0 : for (i = 1; i <= num_gene; i++)
439 : {
440 :
441 0 : if ((Gene) i != fail_gene &&
442 0 : edge_table[i].unused_edges != -1)
443 : {
444 :
445 0 : remaining_edges--;
446 :
447 0 : if (rand_decision == remaining_edges)
448 0 : return i;
449 : }
450 : }
451 :
452 0 : elog(LOG, "no edge found via random decision with remaining edges");
453 : }
454 :
455 : /*
456 : * edge table seems to be empty; this happens sometimes on the last point
457 : * due to the fact that the first point is removed from the table even
458 : * though only one of its edges has been determined
459 : */
460 :
461 : else
462 : { /* occurs only at the last point in the tour;
463 : * simply look for the point which is not yet
464 : * used */
465 :
466 0 : for (i = 1; i <= num_gene; i++)
467 0 : if (edge_table[i].unused_edges >= 0)
468 0 : return (Gene) i;
469 :
470 0 : elog(LOG, "no edge found via looking for the last unused point");
471 : }
472 :
473 :
474 : /* ... should never be reached */
475 0 : elog(ERROR, "no edge found");
476 : return 0; /* to keep the compiler quiet */
477 : }
478 :
479 : #endif /* defined(ERX) */
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