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 : /* contributed by:
12 : =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
13 : * Martin Utesch * Institute of Automatic Control *
14 : = = University of Mining and Technology =
15 : * utesch@aut.tu-freiberg.de * Freiberg, Germany *
16 : =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
17 : */
18 :
19 : /* the edge recombination algorithm is adopted from Genitor : */
20 : /*************************************************************/
21 : /* */
22 : /* Copyright (c) 1990 */
23 : /* Darrell L. Whitley */
24 : /* Computer Science Department */
25 : /* Colorado State University */
26 : /* */
27 : /* Permission is hereby granted to copy all or any part of */
28 : /* this program for free distribution. The author's name */
29 : /* and this copyright notice must be included in any copy. */
30 : /* */
31 : /*************************************************************/
32 :
33 :
34 : #include "postgres.h"
35 : #include "optimizer/geqo.h"
36 :
37 : #if defined(ERX)
38 :
39 : #include "optimizer/geqo_random.h"
40 : #include "optimizer/geqo_recombination.h"
41 :
42 : static int gimme_edge(PlannerInfo *root, Gene gene1, Gene gene2, Edge *edge_table);
43 : static void remove_gene(PlannerInfo *root, Gene gene, Edge edge, Edge *edge_table);
44 : static Gene gimme_gene(PlannerInfo *root, Edge edge, Edge *edge_table);
45 :
46 : static Gene edge_failure(PlannerInfo *root, Gene *gene, int index, Edge *edge_table, int num_gene);
47 :
48 :
49 : /* alloc_edge_table
50 : *
51 : * allocate memory for edge table
52 : *
53 : */
54 :
55 : Edge *
56 21 : alloc_edge_table(PlannerInfo *root, int num_gene)
57 : {
58 : Edge *edge_table;
59 :
60 : /*
61 : * palloc one extra location so that nodes numbered 1..n can be indexed
62 : * directly; 0 will not be used
63 : */
64 :
65 21 : edge_table = palloc_array(Edge, num_gene + 1);
66 :
67 21 : return edge_table;
68 : }
69 :
70 : /* free_edge_table
71 : *
72 : * deallocate memory of edge table
73 : *
74 : */
75 : void
76 21 : free_edge_table(PlannerInfo *root, Edge *edge_table)
77 : {
78 21 : pfree(edge_table);
79 21 : }
80 :
81 : /* gimme_edge_table
82 : *
83 : * fills a data structure which represents the set of explicit
84 : * edges between points in the (2) input genes
85 : *
86 : * assumes circular tours and bidirectional edges
87 : *
88 : * gimme_edge() will set "shared" edges to negative values
89 : *
90 : * returns average number edges/city in range 2.0 - 4.0
91 : * where 2.0=homogeneous; 4.0=diverse
92 : *
93 : */
94 : float
95 1092 : gimme_edge_table(PlannerInfo *root, Gene *tour1, Gene *tour2,
96 : int num_gene, Edge *edge_table)
97 : {
98 : int i,
99 : index1,
100 : index2;
101 : int edge_total; /* total number of unique edges in two genes */
102 :
103 : /* at first clear the edge table's old data */
104 3852 : for (i = 1; i <= num_gene; i++)
105 : {
106 2760 : edge_table[i].total_edges = 0;
107 2760 : edge_table[i].unused_edges = 0;
108 : }
109 :
110 : /* fill edge table with new data */
111 :
112 1092 : edge_total = 0;
113 :
114 3852 : for (index1 = 0; index1 < num_gene; index1++)
115 : {
116 : /*
117 : * presume the tour is circular, i.e. 1->2, 2->3, 3->1 this operation
118 : * maps n back to 1
119 : */
120 :
121 2760 : index2 = (index1 + 1) % num_gene;
122 :
123 : /*
124 : * edges are bidirectional, i.e. 1->2 is same as 2->1 call gimme_edge
125 : * twice per edge
126 : */
127 :
128 2760 : edge_total += gimme_edge(root, tour1[index1], tour1[index2], edge_table);
129 2760 : gimme_edge(root, tour1[index2], tour1[index1], edge_table);
130 :
131 2760 : edge_total += gimme_edge(root, tour2[index1], tour2[index2], edge_table);
132 2760 : gimme_edge(root, tour2[index2], tour2[index1], edge_table);
133 : }
134 :
135 : /* return average number of edges per index */
136 1092 : return ((float) (edge_total * 2) / (float) num_gene);
137 : }
138 :
139 : /* gimme_edge
140 : *
141 : * registers edge from city1 to city2 in input edge table
142 : *
143 : * no assumptions about directionality are made;
144 : * therefore it is up to the calling routine to
145 : * call gimme_edge twice to make a bi-directional edge
146 : * between city1 and city2;
147 : * uni-directional edges are possible as well (just call gimme_edge
148 : * once with the direction from city1 to city2)
149 : *
150 : * returns 1 if edge was not already registered and was just added;
151 : * 0 if edge was already registered and edge_table is unchanged
152 : */
153 : static int
154 11040 : gimme_edge(PlannerInfo *root, Gene gene1, Gene gene2, Edge *edge_table)
155 : {
156 : int i;
157 : int edges;
158 11040 : int city1 = (int) gene1;
159 11040 : int city2 = (int) gene2;
160 :
161 :
162 : /* check whether edge city1->city2 already exists */
163 11040 : edges = edge_table[city1].total_edges;
164 :
165 13959 : for (i = 0; i < edges; i++)
166 : {
167 9657 : if ((Gene) abs(edge_table[city1].edge_list[i]) == city2)
168 : {
169 :
170 : /* mark shared edges as negative */
171 6738 : edge_table[city1].edge_list[i] = 0 - city2;
172 :
173 6738 : return 0;
174 : }
175 : }
176 :
177 : /* add city1->city2; */
178 4302 : edge_table[city1].edge_list[edges] = city2;
179 :
180 : /* increment the number of edges from city1 */
181 4302 : edge_table[city1].total_edges++;
182 4302 : edge_table[city1].unused_edges++;
183 :
184 4302 : return 1;
185 : }
186 :
187 : /* gimme_tour
188 : *
189 : * creates a new tour using edges from the edge table.
190 : * priority is given to "shared" edges (i.e. edges which
191 : * all parent genes possess and are marked as negative
192 : * in the edge table.)
193 : *
194 : */
195 : int
196 1092 : gimme_tour(PlannerInfo *root, Edge *edge_table, Gene *new_gene, int num_gene)
197 : {
198 : int i;
199 1092 : int edge_failures = 0;
200 :
201 : /* choose int between 1 and num_gene */
202 1092 : new_gene[0] = (Gene) geqo_randint(root, num_gene, 1);
203 :
204 2760 : for (i = 1; i < num_gene; i++)
205 : {
206 : /*
207 : * as each point is entered into the tour, remove it from the edge
208 : * table
209 : */
210 :
211 1668 : remove_gene(root, new_gene[i - 1], edge_table[(int) new_gene[i - 1]], edge_table);
212 :
213 : /* find destination for the newly entered point */
214 :
215 1668 : if (edge_table[new_gene[i - 1]].unused_edges > 0)
216 1668 : new_gene[i] = gimme_gene(root, edge_table[(int) new_gene[i - 1]], edge_table);
217 :
218 : else
219 : { /* cope with fault */
220 0 : edge_failures++;
221 :
222 0 : new_gene[i] = edge_failure(root, new_gene, i - 1, edge_table, num_gene);
223 : }
224 :
225 : /* mark this node as incorporated */
226 1668 : edge_table[(int) new_gene[i - 1]].unused_edges = -1;
227 : } /* for (i=1; i<num_gene; i++) */
228 :
229 1092 : return edge_failures;
230 : }
231 :
232 : /* remove_gene
233 : *
234 : * removes input gene from edge_table.
235 : * input edge is used
236 : * to identify deletion locations within edge table.
237 : *
238 : */
239 : static void
240 1668 : remove_gene(PlannerInfo *root, Gene gene, Edge edge, Edge *edge_table)
241 : {
242 : int i,
243 : j;
244 : int possess_edge;
245 : int genes_remaining;
246 :
247 : /*
248 : * do for every gene known to have an edge to input gene (i.e. in
249 : * edge_list for input edge)
250 : */
251 :
252 3819 : for (i = 0; i < edge.unused_edges; i++)
253 : {
254 2151 : possess_edge = abs(edge.edge_list[i]);
255 2151 : genes_remaining = edge_table[possess_edge].unused_edges;
256 :
257 : /* find the input gene in all edge_lists and delete it */
258 2883 : for (j = 0; j < genes_remaining; j++)
259 : {
260 :
261 2883 : if ((Gene) abs(edge_table[possess_edge].edge_list[j]) == gene)
262 : {
263 :
264 2151 : edge_table[possess_edge].unused_edges--;
265 :
266 2151 : edge_table[possess_edge].edge_list[j] =
267 2151 : edge_table[possess_edge].edge_list[genes_remaining - 1];
268 :
269 2151 : break;
270 : }
271 : }
272 : }
273 1668 : }
274 :
275 : /* gimme_gene
276 : *
277 : * priority is given to "shared" edges
278 : * (i.e. edges which both genes possess)
279 : *
280 : */
281 : static Gene
282 1668 : gimme_gene(PlannerInfo *root, Edge edge, Edge *edge_table)
283 : {
284 : int i;
285 : Gene friend;
286 : int minimum_edges;
287 1668 : int minimum_count = -1;
288 : int rand_decision;
289 :
290 : /*
291 : * no point has edges to more than 4 other points thus, this contrived
292 : * minimum will be replaced
293 : */
294 :
295 1668 : minimum_edges = 5;
296 :
297 : /* consider candidate destination points in edge list */
298 :
299 2121 : for (i = 0; i < edge.unused_edges; i++)
300 : {
301 1926 : friend = (Gene) edge.edge_list[i];
302 :
303 : /*
304 : * give priority to shared edges that are negative; so return 'em
305 : */
306 :
307 : /*
308 : * negative values are caught here so we need not worry about
309 : * converting to absolute values
310 : */
311 1926 : if (friend < 0)
312 1473 : return (Gene) abs(friend);
313 :
314 :
315 : /*
316 : * give priority to candidates with fewest remaining unused edges;
317 : * find out what the minimum number of unused edges is
318 : * (minimum_edges); if there is more than one candidate with the
319 : * minimum number of unused edges keep count of this number
320 : * (minimum_count);
321 : */
322 :
323 : /*
324 : * The test for minimum_count can probably be removed at some point
325 : * but comments should probably indicate exactly why it is guaranteed
326 : * that the test will always succeed the first time around. If it can
327 : * fail then the code is in error
328 : */
329 :
330 :
331 453 : if (edge_table[(int) friend].unused_edges < minimum_edges)
332 : {
333 249 : minimum_edges = edge_table[(int) friend].unused_edges;
334 249 : minimum_count = 1;
335 : }
336 204 : else if (minimum_count == -1)
337 0 : elog(ERROR, "minimum_count not set");
338 204 : else if (edge_table[(int) friend].unused_edges == minimum_edges)
339 204 : minimum_count++;
340 : } /* for (i=0; i<edge.unused_edges; i++) */
341 :
342 :
343 : /* random decision of the possible candidates to use */
344 195 : rand_decision = geqo_randint(root, minimum_count - 1, 0);
345 :
346 :
347 285 : for (i = 0; i < edge.unused_edges; i++)
348 : {
349 285 : friend = (Gene) edge.edge_list[i];
350 :
351 : /* return the chosen candidate point */
352 285 : if (edge_table[(int) friend].unused_edges == minimum_edges)
353 : {
354 285 : minimum_count--;
355 :
356 285 : if (minimum_count == rand_decision)
357 195 : return friend;
358 : }
359 : }
360 :
361 : /* ... should never be reached */
362 0 : elog(ERROR, "neither shared nor minimum number nor random edge found");
363 : return 0; /* to keep the compiler quiet */
364 : }
365 :
366 : /* edge_failure
367 : *
368 : * routine for handling edge failure
369 : *
370 : */
371 : static Gene
372 0 : edge_failure(PlannerInfo *root, Gene *gene, int index, Edge *edge_table, int num_gene)
373 : {
374 : int i;
375 0 : Gene fail_gene = gene[index];
376 0 : int remaining_edges = 0;
377 0 : int four_count = 0;
378 : int rand_decision;
379 :
380 :
381 : /*
382 : * how many edges remain? how many gene with four total (initial) edges
383 : * remain?
384 : */
385 :
386 0 : for (i = 1; i <= num_gene; i++)
387 : {
388 0 : if ((edge_table[i].unused_edges != -1) && (i != (int) fail_gene))
389 : {
390 0 : remaining_edges++;
391 :
392 0 : if (edge_table[i].total_edges == 4)
393 0 : four_count++;
394 : }
395 : }
396 :
397 : /*
398 : * random decision of the gene with remaining edges and whose total_edges
399 : * == 4
400 : */
401 :
402 0 : if (four_count != 0)
403 : {
404 :
405 0 : rand_decision = geqo_randint(root, four_count - 1, 0);
406 :
407 0 : for (i = 1; i <= num_gene; i++)
408 : {
409 :
410 0 : if ((Gene) i != fail_gene &&
411 0 : edge_table[i].unused_edges != -1 &&
412 0 : edge_table[i].total_edges == 4)
413 : {
414 :
415 0 : four_count--;
416 :
417 0 : if (rand_decision == four_count)
418 0 : return (Gene) i;
419 : }
420 : }
421 :
422 0 : elog(LOG, "no edge found via random decision and total_edges == 4");
423 : }
424 0 : else if (remaining_edges != 0)
425 : {
426 : /* random decision of the gene with remaining edges */
427 0 : rand_decision = geqo_randint(root, remaining_edges - 1, 0);
428 :
429 0 : for (i = 1; i <= num_gene; i++)
430 : {
431 :
432 0 : if ((Gene) i != fail_gene &&
433 0 : edge_table[i].unused_edges != -1)
434 : {
435 :
436 0 : remaining_edges--;
437 :
438 0 : if (rand_decision == remaining_edges)
439 0 : return i;
440 : }
441 : }
442 :
443 0 : elog(LOG, "no edge found via random decision with remaining edges");
444 : }
445 :
446 : /*
447 : * edge table seems to be empty; this happens sometimes on the last point
448 : * due to the fact that the first point is removed from the table even
449 : * though only one of its edges has been determined
450 : */
451 :
452 : else
453 : { /* occurs only at the last point in the tour;
454 : * simply look for the point which is not yet
455 : * used */
456 :
457 0 : for (i = 1; i <= num_gene; i++)
458 0 : if (edge_table[i].unused_edges >= 0)
459 0 : return (Gene) i;
460 :
461 0 : elog(LOG, "no edge found via looking for the last unused point");
462 : }
463 :
464 :
465 : /* ... should never be reached */
466 0 : elog(ERROR, "no edge found");
467 : return 0; /* to keep the compiler quiet */
468 : }
469 :
470 : #endif /* defined(ERX) */
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