1 /*------------------------------------------------------------------------
2 *
3 * geqo_cx.c
4 *
5 * cycle crossover [CX] routines;
6 * CX operator according to Oliver et al
7 * (Proc 2nd Int'l Conf on GA's)
8 *
9 * src/backend/optimizer/geqo/geqo_cx.c
10 *
11 *-------------------------------------------------------------------------
12 */
13
14 /* contributed by:
15 =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
16 * Martin Utesch * Institute of Automatic Control *
17 = = University of Mining and Technology =
18 * utesch@aut.tu-freiberg.de * Freiberg, Germany *
19 =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
20 */
21
22 /* the cx algorithm is adopted from Genitor : */
23 /*************************************************************/
24 /* */
25 /* Copyright (c) 1990 */
26 /* Darrell L. Whitley */
27 /* Computer Science Department */
28 /* Colorado State University */
29 /* */
30 /* Permission is hereby granted to copy all or any part of */
31 /* this program for free distribution. The author's name */
32 /* and this copyright notice must be included in any copy. */
33 /* */
34 /*************************************************************/
35
36
37 #include "postgres.h"
38 #include "optimizer/geqo_recombination.h"
39 #include "optimizer/geqo_random.h"
40
41
42 /* cx
43 *
44 * cycle crossover
45 */
46 int
cx(PlannerInfo * root,Gene * tour1,Gene * tour2,Gene * offspring,int num_gene,City * city_table)47 cx(PlannerInfo *root, Gene *tour1, Gene *tour2, Gene *offspring,
48 int num_gene, City *city_table)
49 {
50 int i,
51 start_pos,
52 curr_pos;
53 int count = 0;
54 int num_diffs = 0;
55
56 /* initialize city table */
57 for (i = 1; i <= num_gene; i++)
58 {
59 city_table[i].used = 0;
60 city_table[tour2[i - 1]].tour2_position = i - 1;
61 city_table[tour1[i - 1]].tour1_position = i - 1;
62 }
63
64 /* choose random cycle starting position */
65 start_pos = geqo_randint(root, num_gene - 1, 0);
66
67 /* child inherits first city */
68 offspring[start_pos] = tour1[start_pos];
69
70 /* begin cycle with tour1 */
71 curr_pos = start_pos;
72 city_table[(int) tour1[start_pos]].used = 1;
73
74 count++;
75
76 /* cx main part */
77
78
79 /* STEP 1 */
80
81 while (tour2[curr_pos] != tour1[start_pos])
82 {
83 city_table[(int) tour2[curr_pos]].used = 1;
84 curr_pos = city_table[(int) tour2[curr_pos]].tour1_position;
85 offspring[curr_pos] = tour1[curr_pos];
86 count++;
87 }
88
89
90 /* STEP 2 */
91
92 /* failed to create a complete tour */
93 if (count < num_gene)
94 {
95 for (i = 1; i <= num_gene; i++)
96 {
97 if (!city_table[i].used)
98 {
99 offspring[city_table[i].tour2_position] =
100 tour2[(int) city_table[i].tour2_position];
101 count++;
102 }
103 }
104 }
105
106
107 /* STEP 3 */
108
109 /* still failed to create a complete tour */
110 if (count < num_gene)
111 {
112
113 /* count the number of differences between mom and offspring */
114 for (i = 0; i < num_gene; i++)
115 if (tour1[i] != offspring[i])
116 num_diffs++;
117
118 }
119
120 return num_diffs;
121 }
122