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Diffstat (limited to 'glpk-5.0/src/misc/wclique1.c')
| -rw-r--r-- | glpk-5.0/src/misc/wclique1.c | 315 |
1 files changed, 315 insertions, 0 deletions
diff --git a/glpk-5.0/src/misc/wclique1.c b/glpk-5.0/src/misc/wclique1.c new file mode 100644 index 0000000..c0cb082 --- /dev/null +++ b/glpk-5.0/src/misc/wclique1.c @@ -0,0 +1,315 @@ +/* wclique1.c (maximum weight clique, greedy heuristic) */ + +/*********************************************************************** +* This code is part of GLPK (GNU Linear Programming Kit). +* Copyright (C) 2012-2018 Free Software Foundation, Inc. +* Written by Andrew Makhorin <mao@gnu.org>. +* +* GLPK is free software: you can redistribute it and/or modify it +* under the terms of the GNU General Public License as published by +* the Free Software Foundation, either version 3 of the License, or +* (at your option) any later version. +* +* GLPK is distributed in the hope that it will be useful, but WITHOUT +* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY +* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public +* License for more details. +* +* You should have received a copy of the GNU General Public License +* along with GLPK. If not, see <http://www.gnu.org/licenses/>. +***********************************************************************/ + +#include "env.h" +#include "wclique1.h" + +/*********************************************************************** +* NAME +* +* wclique1 - find maximum weight clique with greedy heuristic +* +* SYNOPSIS +* +* #include "wclique1.h" +* int wclique1(int n, const double w[], +* int (*func)(void *info, int i, int ind[]), void *info, int c[]); +* +* DESCRIPTION +* +* The routine wclique1 implements a sequential greedy heuristic to +* find maximum weight clique in a given (undirected) graph G = (V, E). +* +* The parameter n specifies the number of vertices |V| in the graph, +* n >= 0. +* +* The array w specifies vertex weights in locations w[i], i = 1,...,n. +* All weights must be non-negative. +* +* The formal routine func specifies the graph. For a given vertex i, +* 1 <= i <= n, it stores indices of all vertices adjacent to vertex i +* in locations ind[1], ..., ind[deg], where deg is the degree of +* vertex i, 0 <= deg < n, returned on exit. Note that self-loops and +* multiple edges are not allowed. +* +* The parameter info is a cookie passed to the routine func. +* +* On exit the routine wclique1 stores vertex indices included in +* the clique found to locations c[1], ..., c[size], where size is the +* clique size returned by the routine, 0 <= size <= n. +* +* RETURNS +* +* The routine wclique1 returns the size of the clique found. */ + +struct vertex { int i; double cw; }; + +static int CDECL fcmp(const void *xx, const void *yy) +{ const struct vertex *x = xx, *y = yy; + if (x->cw > y->cw) return -1; + if (x->cw < y->cw) return +1; + return 0; +} + +int wclique1(int n, const double w[], + int (*func)(void *info, int i, int ind[]), void *info, int c[]) +{ struct vertex *v_list; + int deg, c_size, d_size, i, j, k, kk, l, *ind, *c_list, *d_list, + size = 0; + double c_wght, d_wght, *sw, best = 0.0; + char *d_flag, *skip; + /* perform sanity checks */ + xassert(n >= 0); + for (i = 1; i <= n; i++) + xassert(w[i] >= 0.0); + /* if the graph is empty, nothing to do */ + if (n == 0) goto done; + /* allocate working arrays */ + ind = xcalloc(1+n, sizeof(int)); + v_list = xcalloc(1+n, sizeof(struct vertex)); + c_list = xcalloc(1+n, sizeof(int)); + d_list = xcalloc(1+n, sizeof(int)); + d_flag = xcalloc(1+n, sizeof(char)); + skip = xcalloc(1+n, sizeof(char)); + sw = xcalloc(1+n, sizeof(double)); + /* build the vertex list */ + for (i = 1; i <= n; i++) + { v_list[i].i = i; + /* compute the cumulative weight of each vertex i, which is + * cw[i] = w[i] + sum{j : (i,j) in E} w[j] */ + v_list[i].cw = w[i]; + deg = func(info, i, ind); + xassert(0 <= deg && deg < n); + for (k = 1; k <= deg; k++) + { j = ind[k]; + xassert(1 <= j && j <= n && j != i); + v_list[i].cw += w[j]; + } + } + /* sort the vertex list to access vertices in descending order of + * cumulative weights */ + qsort(&v_list[1], n, sizeof(struct vertex), fcmp); + /* initially all vertices are unmarked */ + memset(&skip[1], 0, sizeof(char) * n); + /* clear flags of all vertices */ + memset(&d_flag[1], 0, sizeof(char) * n); + /* look through all vertices of the graph */ + for (l = 1; l <= n; l++) + { /* take vertex i */ + i = v_list[l].i; + /* if this vertex was already included in one of previosuly + * constructed cliques, skip it */ + if (skip[i]) continue; + /* use vertex i as the initial clique vertex */ + c_size = 1; /* size of current clique */ + c_list[1] = i; /* list of vertices in current clique */ + c_wght = w[i]; /* weight of current clique */ + /* determine the candidate set D = { j : (i,j) in E } */ + d_size = func(info, i, d_list); + xassert(0 <= d_size && d_size < n); + d_wght = 0.0; /* weight of set D */ + for (k = 1; k <= d_size; k++) + { j = d_list[k]; + xassert(1 <= j && j <= n && j != i); + xassert(!d_flag[j]); + d_flag[j] = 1; + d_wght += w[j]; + } + /* check an upper bound to the final clique weight */ + if (c_wght + d_wght < best + 1e-5 * (1.0 + fabs(best))) + { /* skip constructing the current clique */ + goto next; + } + /* compute the summary weight of each vertex i in D, which is + * sw[i] = w[i] + sum{j in D and (i,j) in E} w[j] */ + for (k = 1; k <= d_size; k++) + { i = d_list[k]; + sw[i] = w[i]; + /* consider vertices adjacent to vertex i */ + deg = func(info, i, ind); + xassert(0 <= deg && deg < n); + for (kk = 1; kk <= deg; kk++) + { j = ind[kk]; + xassert(1 <= j && j <= n && j != i); + if (d_flag[j]) sw[i] += w[j]; + } + } + /* grow the current clique by adding vertices from D */ + while (d_size > 0) + { /* check an upper bound to the final clique weight */ + if (c_wght + d_wght < best + 1e-5 * (1.0 + fabs(best))) + { /* skip constructing the current clique */ + goto next; + } + /* choose vertex i in D having maximal summary weight */ + i = d_list[1]; + for (k = 2; k <= d_size; k++) + { j = d_list[k]; + if (sw[i] < sw[j]) i = j; + } + /* include vertex i in the current clique */ + c_size++; + c_list[c_size] = i; + c_wght += w[i]; + /* remove all vertices not adjacent to vertex i, including + * vertex i itself, from the candidate set D */ + deg = func(info, i, ind); + xassert(0 <= deg && deg < n); + for (k = 1; k <= deg; k++) + { j = ind[k]; + xassert(1 <= j && j <= n && j != i); + /* vertex j is adjacent to vertex i */ + if (d_flag[j]) + { xassert(d_flag[j] == 1); + /* mark vertex j to keep it in D */ + d_flag[j] = 2; + } + } + kk = d_size, d_size = 0; + for (k = 1; k <= kk; k++) + { j = d_list[k]; + if (d_flag[j] == 1) + { /* remove vertex j from D */ + d_flag[j] = 0; + d_wght -= w[j]; + } + else if (d_flag[j] == 2) + { /* keep vertex j in D */ + d_list[++d_size] = j; + d_flag[j] = 1; + } + else + xassert(d_flag != d_flag); + } + } + /* the current clique has been completely constructed */ + if (best < c_wght) + { best = c_wght; + size = c_size; + xassert(1 <= size && size <= n); + memcpy(&c[1], &c_list[1], size * sizeof(int)); + } +next: /* mark the current clique vertices in order not to use them + * as initial vertices anymore */ + for (k = 1; k <= c_size; k++) + skip[c_list[k]] = 1; + /* set D can be non-empty, so clean up vertex flags */ + for (k = 1; k <= d_size; k++) + d_flag[d_list[k]] = 0; + } + /* free working arrays */ + xfree(ind); + xfree(v_list); + xfree(c_list); + xfree(d_list); + xfree(d_flag); + xfree(skip); + xfree(sw); +done: /* return to the calling program */ + return size; +} + +/**********************************************************************/ + +#ifdef GLP_TEST +#include "glpk.h" +#include "rng.h" + +typedef struct { double w; } v_data; + +#define weight(v) (((v_data *)((v)->data))->w) + +glp_graph *G; + +char *flag; + +int func(void *info, int i, int ind[]) +{ glp_arc *e; + int j, k, deg = 0; + xassert(info == NULL); + xassert(1 <= i && i <= G->nv); + /* look through incoming arcs */ + for (e = G->v[i]->in; e != NULL; e = e->h_next) + { j = e->tail->i; /* j->i */ + if (j != i && !flag[j]) ind[++deg] = j, flag[j] = 1; + } + /* look through outgoing arcs */ + for (e = G->v[i]->out; e != NULL; e = e->t_next) + { j = e->head->i; /* i->j */ + if (j != i && !flag[j]) ind[++deg] = j, flag[j] = 1; + } + /* clear the flag array */ + xassert(deg < G->nv); + for (k = 1; k <= deg; k++) flag[ind[k]] = 0; + return deg; +} + +int main(int argc, char *argv[]) +{ RNG *rand; + int i, k, kk, size, *c, *ind, deg; + double *w, sum, t; + /* read graph in DIMACS format */ + G = glp_create_graph(sizeof(v_data), 0); + xassert(argc == 2); + xassert(glp_read_ccdata(G, offsetof(v_data, w), argv[1]) == 0); + /* print the number of connected components */ + xprintf("nc = %d\n", glp_weak_comp(G, -1)); + /* assign random weights unformly distributed in [1,100] */ + w = xcalloc(1+G->nv, sizeof(double)); + rand = rng_create_rand(); + for (i = 1; i <= G->nv; i++) +#if 0 + w[i] = weight(G->v[i]) = 1.0; +#else + w[i] = weight(G->v[i]) = rng_unif_rand(rand, 100) + 1; +#endif + /* write graph in DIMACS format */ + xassert(glp_write_ccdata(G, offsetof(v_data, w), "graph") == 0); + /* find maximum weight clique */ + c = xcalloc(1+G->nv, sizeof(int)); + flag = xcalloc(1+G->nv, sizeof(char)); + memset(&flag[1], 0, G->nv); + t = xtime(); + size = wclique1(G->nv, w, func, NULL, c); + xprintf("Time used: %.1f s\n", xdifftime(xtime(), t)); + /* check the clique found */ + ind = xcalloc(1+G->nv, sizeof(int)); + for (k = 1; k <= size; k++) + { i = c[k]; + deg = func(NULL, i, ind); + for (kk = 1; kk <= size; kk++) + flag[c[kk]] = 1; + flag[i] = 0; + for (kk = 1; kk <= deg; kk++) + flag[ind[kk]] = 0; + for (kk = 1; kk <= size; kk++) + xassert(flag[c[kk]] == 0); + } + /* compute the clique weight */ + sum = 0.0; + for (i = 1; i <= size; i++) + sum += w[c[i]]; + xprintf("size = %d; sum = %g\n", size, sum); + return 0; +} +#endif + +/* eof */ |