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
31 #include "bipartite.h"
39 bipartite_t *bipartite_new(int n_left, int n_right)
41 bipartite_t *gr = XMALLOCFZ(bipartite_t, adj, n_left);
45 gr->n_right = n_right;
47 for (i = 0; i < n_left; ++i)
48 gr->adj[i] = bitset_malloc(n_right);
53 void bipartite_free(bipartite_t *gr)
56 for (i = 0; i < gr->n_left; ++i)
57 bitset_free(gr->adj[i]);
61 void bipartite_add(bipartite_t *gr, int i, int j)
63 assert(i < gr->n_left && j < gr->n_right);
64 bitset_set(gr->adj[i], j);
67 void bipartite_remv(bipartite_t *gr, int i, int j)
69 assert(i < gr->n_left && j < gr->n_right);
70 bitset_clear(gr->adj[i], j);
73 int bipartite_adj(const bipartite_t *gr, int i, int j)
75 assert(i < gr->n_left && j < gr->n_right);
76 return bitset_is_set(gr->adj[i], j);
79 static int apply_alternating_path(const bipartite_t *gr, int *matching,
80 bitset_t *matched_left, bitset_t *matched_right)
83 int done_something = 0;
84 bitset_t *tmp = bitset_alloca(gr->n_right);
86 for (left = 0; left < gr->n_left; ++left) {
87 bitset_t *left_adj = gr->adj[left];
90 bitset_copy(tmp, left_adj);
92 if (matching[left] >= 0) {
93 int old_right = matching[left];
95 /* Check of all neighbors of the left node are already matched.
96 * We cannot improve this edge then. */
97 if (bitset_contains(left_adj, matched_right))
100 bitset_andnot(tmp, matched_right);
101 right = bitset_next_set(tmp, 0);
106 We have to find another left node which has the old right one as a neighbor.
107 This node must not be part of a matching
109 for (i = 0; i < gr->n_left; ++i)
110 if (i != left && bitset_is_set(gr->adj[i], old_right) && !bitset_is_set(matched_left, i))
113 /* If no such node can be found, exit. */
117 /* Else, we can improve this edge. */
118 matching[left] = right;
119 matching[i] = old_right;
120 bitset_set(matched_left, i);
121 bitset_set(matched_right, right);
126 /* We have to create a new single edge */
128 assert(!bitset_is_set(matched_left, left));
130 bitset_andnot(tmp, matched_right);
131 if (bitset_is_empty(tmp))
134 right = bitset_next_set(tmp, 0);
135 assert(!bitset_is_set(matched_right, right));
136 matching[left] = right;
137 bitset_set(matched_left, left);
138 bitset_set(matched_right, right);
143 return done_something;
146 void bipartite_matching(const bipartite_t *gr, int *matching)
148 bitset_t *matched_left = bitset_alloca(gr->n_left);
149 bitset_t *matched_right = bitset_alloca(gr->n_right);
151 memset(matching, -1, gr->n_left * sizeof(int));
152 while (apply_alternating_path(gr, matching, matched_left, matched_right)) {
156 void bipartite_dump_f(FILE *f, const bipartite_t *gr)
160 for (i = 0; i < gr->n_left; ++i) {
161 fprintf(f, "%d: ", i);
162 bitset_fprint(f, gr->adj[i]);
167 void bipartite_dump(const char *name, const bipartite_t *gr)
169 FILE *f = fopen(name, "w");
172 bipartite_dump_f(f, gr);