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geqo_cx.c
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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"
39 #include "optimizer/geqo_random.h"
40 
41 #if defined(CX)
42 
43 /* cx
44  *
45  * cycle crossover
46  */
47 int
48 cx(PlannerInfo *root, Gene *tour1, Gene *tour2, Gene *offspring,
49  int num_gene, City *city_table)
50 {
51  int i,
52  start_pos,
53  curr_pos;
54  int count = 0;
55  int num_diffs = 0;
56 
57  /* initialize city table */
58  for (i = 1; i <= num_gene; i++)
59  {
60  city_table[i].used = 0;
61  city_table[tour2[i - 1]].tour2_position = i - 1;
62  city_table[tour1[i - 1]].tour1_position = i - 1;
63  }
64 
65  /* choose random cycle starting position */
66  start_pos = geqo_randint(root, num_gene - 1, 0);
67 
68  /* child inherits first city */
69  offspring[start_pos] = tour1[start_pos];
70 
71  /* begin cycle with tour1 */
72  curr_pos = start_pos;
73  city_table[(int) tour1[start_pos]].used = 1;
74 
75  count++;
76 
77  /* cx main part */
78 
79 
80 /* STEP 1 */
81 
82  while (tour2[curr_pos] != tour1[start_pos])
83  {
84  city_table[(int) tour2[curr_pos]].used = 1;
85  curr_pos = city_table[(int) tour2[curr_pos]].tour1_position;
86  offspring[curr_pos] = tour1[curr_pos];
87  count++;
88  }
89 
90 
91 /* STEP 2 */
92 
93  /* failed to create a complete tour */
94  if (count < num_gene)
95  {
96  for (i = 1; i <= num_gene; i++)
97  {
98  if (!city_table[i].used)
99  {
100  offspring[city_table[i].tour2_position] =
101  tour2[(int) city_table[i].tour2_position];
102  count++;
103  }
104  }
105  }
106 
107 
108 /* STEP 3 */
109 
110  /* still failed to create a complete tour */
111  if (count < num_gene)
112  {
113 
114  /* count the number of differences between mom and offspring */
115  for (i = 0; i < num_gene; i++)
116  if (tour1[i] != offspring[i])
117  num_diffs++;
118 
119  }
120 
121  return num_diffs;
122 }
123 
124 #endif /* defined(CX) */
#define geqo_randint(root, upper, lower)
Definition: geqo_random.h:38
int Gene
Definition: geqo_gene.h:30
int cx(PlannerInfo *root, Gene *tour1, Gene *tour2, Gene *offspring, int num_gene, City *city_table)
int tour1_position
int tour2_position
int i