2 * Copyright (C) 1995-2008 University of Karlsruhe. All right reserved.
4 * This file is part of libFirm.
6 * This file may be distributed and/or modified under the terms of the
7 * GNU General Public License version 2 as published by the Free Software
8 * Foundation and appearing in the file LICENSE.GPL included in the
9 * packaging of this file.
11 * Licensees holding valid libFirm Professional Edition licenses may use
12 * this file in accordance with the libFirm Commercial License.
13 * Agreement provided with the Software.
15 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
16 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * @brief Specialized implementation for perfect bipartite matching.
23 * @author Sebastian Hack
34 #include "bipartite.h"
42 bipartite_t *bipartite_new(int n_left, int n_right)
47 size = n_left > 0 ? n_left - 1 : 0;
48 gr = xmalloc(sizeof(*gr) + size * sizeof(void *));
49 memset(gr, 0, sizeof(*gr));
52 gr->n_right = n_right;
54 for(i = 0; i < n_left; ++i)
55 gr->adj[i] = bitset_malloc(n_right);
60 void bipartite_free(bipartite_t *gr)
63 for(i = 0; i < gr->n_left; ++i)
64 bitset_free(gr->adj[i]);
68 void bipartite_add(bipartite_t *gr, int i, int j)
70 assert(i < gr->n_left && j < gr->n_right);
71 bitset_set(gr->adj[i], j);
74 void bipartite_remv(bipartite_t *gr, int i, int j)
76 assert(i < gr->n_left && j < gr->n_right);
77 bitset_clear(gr->adj[i], j);
80 int bipartite_adj(const bipartite_t *gr, int i, int j)
82 assert(i < gr->n_left && j < gr->n_right);
83 return bitset_is_set(gr->adj[i], j);
86 static int apply_alternating_path(const bipartite_t *gr, int *matching,
87 bitset_t *matched_left, bitset_t *matched_right)
90 int done_something = 0;
91 bitset_t *tmp = bitset_alloca(gr->n_right);
93 for(left = 0; left < gr->n_left; ++left) {
94 bitset_t *left_adj = gr->adj[left];
97 bitset_copy(tmp, left_adj);
99 if(matching[left] >= 0) {
100 int old_right = matching[left];
102 /* Check of all neighbors of the left node are already matched.
103 * We cannot improve this edge then. */
104 if(bitset_contains(left_adj, matched_right))
107 bitset_andnot(tmp, matched_right);
108 right = bitset_next_set(tmp, 0);
113 We have to find another left node which has the old right one as a neighbor.
114 This node must not be part of a matching
116 for(i = 0; i < gr->n_left; ++i)
117 if(i != left && bitset_is_set(gr->adj[i], old_right) && !bitset_is_set(matched_left, i))
120 /* If no such node can be found, exit. */
124 /* Else, we can improve this edge. */
125 matching[left] = right;
126 matching[i] = old_right;
127 bitset_set(matched_left, i);
128 bitset_set(matched_right, right);
133 /* We have to create a new single edge */
135 assert(!bitset_is_set(matched_left, left));
137 bitset_andnot(tmp, matched_right);
138 if(bitset_popcnt(tmp) == 0)
141 right = bitset_next_set(tmp, 0);
142 assert(!bitset_is_set(matched_right, right));
143 matching[left] = right;
144 bitset_set(matched_left, left);
145 bitset_set(matched_right, right);
150 return done_something;
153 void bipartite_matching(const bipartite_t *gr, int *matching)
155 bitset_t *matched_left = bitset_alloca(gr->n_left);
156 bitset_t *matched_right = bitset_alloca(gr->n_right);
158 memset(matching, -1, gr->n_left * sizeof(int));
159 while(apply_alternating_path(gr, matching, matched_left, matched_right));
162 void bipartite_dump_f(FILE *f, const bipartite_t *gr)
166 for(i = 0; i < gr->n_left; ++i) {
167 fprintf(f, "%d: ", i);
168 bitset_fprint(f, gr->adj[i]);
173 void bipartite_dump(const char *name, const bipartite_t *gr) {
174 FILE *f = fopen(name, "w");
177 bipartite_dump_f(f, gr);