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geqo_erx.c
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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"
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 *
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  edge_table = (Edge *) palloc((num_gene + 1) * sizeof(Edge));
66 
67  return edge_table;
68 }
69 
70 /* free_edge_table
71  *
72  * deallocate memory of edge table
73  *
74  */
75 void
77 {
78  pfree(edge_table);
79 }
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
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  for (i = 1; i <= num_gene; i++)
105  {
106  edge_table[i].total_edges = 0;
107  edge_table[i].unused_edges = 0;
108  }
109 
110  /* fill edge table with new data */
111 
112  edge_total = 0;
113 
114  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  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  edge_total += gimme_edge(root, tour1[index1], tour1[index2], edge_table);
129  gimme_edge(root, tour1[index2], tour1[index1], edge_table);
130 
131  edge_total += gimme_edge(root, tour2[index1], tour2[index2], edge_table);
132  gimme_edge(root, tour2[index2], tour2[index1], edge_table);
133  }
134 
135  /* return average number of edges per index */
136  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 gimme_edge(PlannerInfo *root, Gene gene1, Gene gene2, Edge *edge_table)
155 {
156  int i;
157  int edges;
158  int city1 = (int) gene1;
159  int city2 = (int) gene2;
160 
161 
162  /* check whether edge city1->city2 already exists */
163  edges = edge_table[city1].total_edges;
164 
165  for (i = 0; i < edges; i++)
166  {
167  if ((Gene) abs(edge_table[city1].edge_list[i]) == city2)
168  {
169 
170  /* mark shared edges as negative */
171  edge_table[city1].edge_list[i] = 0 - city2;
172 
173  return 0;
174  }
175  }
176 
177  /* add city1->city2; */
178  edge_table[city1].edge_list[edges] = city2;
179 
180  /* increment the number of edges from city1 */
181  edge_table[city1].total_edges++;
182  edge_table[city1].unused_edges++;
183 
184  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 gimme_tour(PlannerInfo *root, Edge *edge_table, Gene *new_gene, int num_gene)
197 {
198  int i;
199  int edge_failures = 0;
200 
201  /* choose int between 1 and num_gene */
202  new_gene[0] = (Gene) geqo_randint(root, num_gene, 1);
203 
204  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  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  if (edge_table[new_gene[i - 1]].unused_edges > 0)
216  new_gene[i] = gimme_gene(root, edge_table[(int) new_gene[i - 1]], edge_table);
217 
218  else
219  { /* cope with fault */
220  edge_failures++;
221 
222  new_gene[i] = edge_failure(root, new_gene, i - 1, edge_table, num_gene);
223  }
224 
225  /* mark this node as incorporated */
226  edge_table[(int) new_gene[i - 1]].unused_edges = -1;
227  } /* for (i=1; i<num_gene; i++) */
228 
229  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 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  for (i = 0; i < edge.unused_edges; i++)
253  {
254  possess_edge = abs(edge.edge_list[i]);
255  genes_remaining = edge_table[possess_edge].unused_edges;
256 
257  /* find the input gene in all edge_lists and delete it */
258  for (j = 0; j < genes_remaining; j++)
259  {
260 
261  if ((Gene) abs(edge_table[possess_edge].edge_list[j]) == gene)
262  {
263 
264  edge_table[possess_edge].unused_edges--;
265 
266  edge_table[possess_edge].edge_list[j] =
267  edge_table[possess_edge].edge_list[genes_remaining - 1];
268 
269  break;
270  }
271  }
272  }
273 }
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 gimme_gene(PlannerInfo *root, Edge edge, Edge *edge_table)
283 {
284  int i;
285  Gene friend;
286  int minimum_edges;
287  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  minimum_edges = 5;
296 
297  /* consider candidate destination points in edge list */
298 
299  for (i = 0; i < edge.unused_edges; i++)
300  {
301  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  if (friend < 0)
312  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  if (edge_table[(int) friend].unused_edges < minimum_edges)
332  {
333  minimum_edges = edge_table[(int) friend].unused_edges;
334  minimum_count = 1;
335  }
336  else if (minimum_count == -1)
337  elog(ERROR, "minimum_count not set");
338  else if (edge_table[(int) friend].unused_edges == minimum_edges)
339  minimum_count++;
340  } /* for (i=0; i<edge.unused_edges; i++) */
341 
342 
343  /* random decision of the possible candidates to use */
344  rand_decision = geqo_randint(root, minimum_count - 1, 0);
345 
346 
347  for (i = 0; i < edge.unused_edges; i++)
348  {
349  friend = (Gene) edge.edge_list[i];
350 
351  /* return the chosen candidate point */
352  if (edge_table[(int) friend].unused_edges == minimum_edges)
353  {
354  minimum_count--;
355 
356  if (minimum_count == rand_decision)
357  return friend;
358  }
359  }
360 
361  /* ... should never be reached */
362  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 edge_failure(PlannerInfo *root, Gene *gene, int index, Edge *edge_table, int num_gene)
373 {
374  int i;
375  Gene fail_gene = gene[index];
376  int remaining_edges = 0;
377  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  for (i = 1; i <= num_gene; i++)
387  {
388  if ((edge_table[i].unused_edges != -1) && (i != (int) fail_gene))
389  {
390  remaining_edges++;
391 
392  if (edge_table[i].total_edges == 4)
393  four_count++;
394  }
395  }
396 
397  /*
398  * random decision of the gene with remaining edges and whose total_edges
399  * == 4
400  */
401 
402  if (four_count != 0)
403  {
404 
405  rand_decision = geqo_randint(root, four_count - 1, 0);
406 
407  for (i = 1; i <= num_gene; i++)
408  {
409 
410  if ((Gene) i != fail_gene &&
411  edge_table[i].unused_edges != -1 &&
412  edge_table[i].total_edges == 4)
413  {
414 
415  four_count--;
416 
417  if (rand_decision == four_count)
418  return (Gene) i;
419  }
420  }
421 
422  elog(LOG, "no edge found via random decision and total_edges == 4");
423  }
424  else if (remaining_edges != 0)
425  {
426  /* random decision of the gene with remaining edges */
427  rand_decision = geqo_randint(root, remaining_edges - 1, 0);
428 
429  for (i = 1; i <= num_gene; i++)
430  {
431 
432  if ((Gene) i != fail_gene &&
433  edge_table[i].unused_edges != -1)
434  {
435 
436  remaining_edges--;
437 
438  if (rand_decision == remaining_edges)
439  return i;
440  }
441  }
442 
443  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  for (i = 1; i <= num_gene; i++)
458  if (edge_table[i].unused_edges >= 0)
459  return (Gene) i;
460 
461  elog(LOG, "no edge found via looking for the last unused point");
462  }
463 
464 
465  /* ... should never be reached */
466  elog(ERROR, "no edge found");
467  return 0; /* to keep the compiler quiet */
468 }
469 
470 #endif /* defined(ERX) */
#define LOG
Definition: elog.h:31
#define ERROR
Definition: elog.h:39
#define elog(elevel,...)
Definition: elog.h:224
static int gimme_edge(PlannerInfo *root, Gene gene1, Gene gene2, Edge *edge_table)
Definition: geqo_erx.c:154
float gimme_edge_table(PlannerInfo *root, Gene *tour1, Gene *tour2, int num_gene, Edge *edge_table)
Definition: geqo_erx.c:95
void free_edge_table(PlannerInfo *root, Edge *edge_table)
Definition: geqo_erx.c:76
static Gene gimme_gene(PlannerInfo *root, Edge edge, Edge *edge_table)
Definition: geqo_erx.c:282
int gimme_tour(PlannerInfo *root, Edge *edge_table, Gene *new_gene, int num_gene)
Definition: geqo_erx.c:196
static Gene edge_failure(PlannerInfo *root, Gene *gene, int index, Edge *edge_table, int num_gene)
Definition: geqo_erx.c:372
static void remove_gene(PlannerInfo *root, Gene gene, Edge edge, Edge *edge_table)
Definition: geqo_erx.c:240
Edge * alloc_edge_table(PlannerInfo *root, int num_gene)
Definition: geqo_erx.c:56
int Gene
Definition: geqo_gene.h:30
int geqo_randint(PlannerInfo *root, int upper, int lower)
Definition: geqo_random.c:36
struct Edge Edge
int j
Definition: isn.c:74
int i
Definition: isn.c:73
if(TABLE==NULL||TABLE_index==NULL)
Definition: isn.c:77
void pfree(void *pointer)
Definition: mcxt.c:1520
void * palloc(Size size)
Definition: mcxt.c:1316
tree ctl root
Definition: radixtree.h:1880
int unused_edges
Gene edge_list[4]
int total_edges
Definition: type.h:95