nsz Git - libfirm/blob - ir/adt/bipartite.c

   1
   2 #include <stdio.h>
   3 #include <assert.h>
   4
   5 #include "bitset.h"
   6 #include "bipartite.h"
   7
   8 struct _bipartite_t {
   9         int n_left, n_right;
  10         bitset_t **adj;
  11 };
  12
  13 bipartite_t *bipartite_new(int n_left, int n_right)
  14 {
  15         int i;
  16         bipartite_t *gr = malloc(sizeof(*gr));
  17         memset(gr, 0, sizeof(*gr));
  18
  19         gr->n_left = n_left;
  20         gr->n_right = n_right;
  21         gr->adj = malloc(n_left * sizeof(void *));
  22
  23         for(i = 0; i < n_left; ++i)
  24                 gr->adj[i] = bitset_malloc(n_right);
  25
  26         return gr;
  27 }
  28
  29 void bipartite_free(bipartite_t *gr)
  30 {
  31         int i;
  32         for(i = 0; i < gr->n_left; ++i)
  33                 bitset_free(gr->adj[i]);
  34
  35         free(gr->adj);
  36         free(gr);
  37 }
  38
  39 void bipartite_add(bipartite_t *gr, int i, int j)
  40 {
  41         assert(i < gr->n_left && j < gr->n_right);
  42         bitset_set(gr->adj[i], j);
  43 }
  44
  45 void bipartite_remv(bipartite_t *gr, int i, int j)
  46 {
  47         assert(i < gr->n_left && j < gr->n_right);
  48         bitset_clear(gr->adj[i], j);
  49 }
  50
  51 int bipartite_adj(const bipartite_t *gr, int i, int j)
  52 {
  53         assert(i < gr->n_left && j < gr->n_right);
  54         return bitset_is_set(gr->adj[i], j);
  55 }
  56
  57 static int apply_alternating_path(const bipartite_t *gr, int *matching,
  58                 bitset_t *matched_left, bitset_t *matched_right)
  59 {
  60         int left, right;
  61         int done_something = 0;
  62         bitset_t *tmp = bitset_malloc(gr->n_left);
  63
  64         for(left = 0; left < gr->n_left; ++left) {
  65                 bitset_t *left_adj = gr->adj[left];
  66                 int i;
  67
  68                 bitset_copy(tmp, left_adj);
  69
  70                 if(matching[left] >= 0) {
  71                         int old_right = matching[left];
  72
  73                         /* Check of all neighbors of the left node are already matched.
  74                          * We cannot improve this edge then. */
  75                         if(bitset_contains(left_adj, matched_right))
  76                                 continue;
  77
  78                         bitset_andnot(tmp, matched_right);
  79                         right = bitset_next_set(tmp, 0);
  80
  81                         assert(right != -1);
  82
  83                         /* We have to find another left node which has the old right
  84                          * one as a neighbor. */
  85                         for(i = 0; i < gr->n_left; ++i)
  86                                 if(i != left && bitset_is_set(gr->adj[i], old_right))
  87                                         break;
  88
  89                         /* If no such node can be found, exit. */
  90                         if(i >= gr->n_left)
  91                                 continue;
  92
  93                         /* Else, we can improve this edge. */
  94                         matching[left] = right;
  95                         matching[i] = old_right;
  96                         bitset_set(matched_left, i);
  97                         bitset_set(matched_right, right);
  98                         done_something = 1;
  99                 }
 100
 101
 102                 /* We have to create a new single edge */
 103                 else {
 104                         assert(!bitset_is_set(matched_left, left));
 105
 106                         bitset_andnot(tmp, matched_right);
 107                         if(bitset_popcnt(tmp) == 0)
 108                                 continue;
 109
 110                         right = bitset_min(tmp);
 111                         assert(!bitset_is_set(matched_right, right));
 112                         matching[left] = right;
 113                         bitset_set(matched_left, left);
 114                         bitset_set(matched_right, right);
 115                         done_something = 1;
 116                 }
 117         }
 118
 119         bitset_free(tmp);
 120
 121         return done_something;
 122 }
 123
 124 void bipartite_matching(const bipartite_t *gr, int *matching)
 125 {
 126         bitset_t *matched_left = bitset_malloc(gr->n_left);
 127         bitset_t *matched_right = bitset_malloc(gr->n_right);
 128
 129         memset(matching, -1, gr->n_left * sizeof(int));
 130         while(apply_alternating_path(gr, matching, matched_left, matched_right));
 131
 132         bitset_free(matched_left);
 133         bitset_free(matched_right);
 134 }