diff -r d59bea55db9b -r c445c931472f src/glpapi18.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/glpapi18.c	Mon Dec 06 13:09:21 2010 +0100
@@ -0,0 +1,122 @@
+/* glpapi18.c (maximum clique problem) */
+
+/***********************************************************************
+*  This code is part of GLPK (GNU Linear Programming Kit).
+*
+*  Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008,
+*  2009, 2010 Andrew Makhorin, Department for Applied Informatics,
+*  Moscow Aviation Institute, Moscow, Russia. All rights reserved.
+*  E-mail: <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 "glpapi.h"
+#include "glpnet.h"
+
+static void set_edge(int nv, unsigned char a[], int i, int j)
+{     int k;
+      xassert(1 <= j && j < i && i <= nv);
+      k = ((i - 1) * (i - 2)) / 2 + (j - 1);
+      a[k / CHAR_BIT] |=
+         (unsigned char)(1 << ((CHAR_BIT - 1) - k % CHAR_BIT));
+      return;
+}
+
+int glp_wclique_exact(glp_graph *G, int v_wgt, double *sol, int v_set)
+{     /* find maximum weight clique with exact algorithm */
+      glp_arc *e;
+      int i, j, k, len, x, *w, *ind, ret = 0;
+      unsigned char *a;
+      double s, t;
+      if (v_wgt >= 0 && v_wgt > G->v_size - (int)sizeof(double))
+         xerror("glp_wclique_exact: v_wgt = %d; invalid parameter\n",
+            v_wgt);
+      if (v_set >= 0 && v_set > G->v_size - (int)sizeof(int))
+         xerror("glp_wclique_exact: v_set = %d; invalid parameter\n",
+            v_set);
+      if (G->nv == 0)
+      {  /* empty graph has only empty clique */
+         if (sol != NULL) *sol = 0.0;
+         return 0;
+      }
+      /* allocate working arrays */
+      w = xcalloc(1+G->nv, sizeof(int));
+      ind = xcalloc(1+G->nv, sizeof(int));
+      len = G->nv; /* # vertices */
+      len = len * (len - 1) / 2; /* # entries in lower triangle */
+      len = (len + (CHAR_BIT - 1)) / CHAR_BIT; /* # bytes needed */
+      a = xcalloc(len, sizeof(char));
+      memset(a, 0, len * sizeof(char));
+      /* determine vertex weights */
+      s = 0.0;
+      for (i = 1; i <= G->nv; i++)
+      {  if (v_wgt >= 0)
+         {  memcpy(&t, (char *)G->v[i]->data + v_wgt, sizeof(double));
+            if (!(0.0 <= t && t <= (double)INT_MAX && t == floor(t)))
+            {  ret = GLP_EDATA;
+               goto done;
+            }
+            w[i] = (int)t;
+         }
+         else
+            w[i] = 1;
+         s += (double)w[i];
+      }
+      if (s > (double)INT_MAX)
+      {  ret = GLP_EDATA;
+         goto done;
+      }
+      /* build the adjacency matrix */
+      for (i = 1; i <= G->nv; i++)
+      {  for (e = G->v[i]->in; e != NULL; e = e->h_next)
+         {  j = e->tail->i;
+            /* there exists edge (j,i) in the graph */
+            if (i > j) set_edge(G->nv, a, i, j);
+         }
+         for (e = G->v[i]->out; e != NULL; e = e->t_next)
+         {  j = e->head->i;
+            /* there exists edge (i,j) in the graph */
+            if (i > j) set_edge(G->nv, a, i, j);
+         }
+      }
+      /* find maximum weight clique in the graph */
+      len = wclique(G->nv, w, a, ind);
+      /* compute the clique weight */
+      s = 0.0;
+      for (k = 1; k <= len; k++)
+      {  i = ind[k];
+         xassert(1 <= i && i <= G->nv);
+         s += (double)w[i];
+      }
+      if (sol != NULL) *sol = s;
+      /* mark vertices included in the clique */
+      if (v_set >= 0)
+      {  x = 0;
+         for (i = 1; i <= G->nv; i++)
+            memcpy((char *)G->v[i]->data + v_set, &x, sizeof(int));
+         x = 1;
+         for (k = 1; k <= len; k++)
+         {  i = ind[k];
+            memcpy((char *)G->v[i]->data + v_set, &x, sizeof(int));
+         }
+      }
+done: /* free working arrays */
+      xfree(w);
+      xfree(ind);
+      xfree(a);
+      return ret;
+}
+
+/* eof */