/* graph.c (basic graph routines) */

/***********************************************************************
*  This code is part of GLPK (GNU Linear Programming Kit).
*  Copyright (C) 2009-2016 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 "avl.h"
#include "dmp.h"
#include "env.h"
#include "glpk.h"

/* CAUTION: DO NOT CHANGE THE LIMITS BELOW */

#define NV_MAX 100000000 /* = 100*10^6 */
/* maximal number of vertices in the graph */

#define NA_MAX 500000000 /* = 500*10^6 */
/* maximal number of arcs in the graph */

/***********************************************************************
*  NAME
*
*  glp_create_graph - create graph
*
*  SYNOPSIS
*
*  glp_graph *glp_create_graph(int v_size, int a_size);
*
*  DESCRIPTION
*
*  The routine creates a new graph, which initially is empty, i.e. has
*  no vertices and arcs.
*
*  The parameter v_size specifies the size of data associated with each
*  vertex of the graph (0 to 256 bytes).
*
*  The parameter a_size specifies the size of data associated with each
*  arc of the graph (0 to 256 bytes).
*
*  RETURNS
*
*  The routine returns a pointer to the graph created. */

static void create_graph(glp_graph *G, int v_size, int a_size)
{     G->pool = dmp_create_pool();
      G->name = NULL;
      G->nv_max = 50;
      G->nv = G->na = 0;
      G->v = xcalloc(1+G->nv_max, sizeof(glp_vertex *));
      G->index = NULL;
      G->v_size = v_size;
      G->a_size = a_size;
      return;
}

glp_graph *glp_create_graph(int v_size, int a_size)
{     glp_graph *G;
      if (!(0 <= v_size && v_size <= 256))
         xerror("glp_create_graph: v_size = %d; invalid size of vertex "
            "data\n", v_size);
      if (!(0 <= a_size && a_size <= 256))
         xerror("glp_create_graph: a_size = %d; invalid size of arc dat"
            "a\n", a_size);
      G = xmalloc(sizeof(glp_graph));
      create_graph(G, v_size, a_size);
      return G;
}

/***********************************************************************
*  NAME
*
*  glp_set_graph_name - assign (change) graph name
*
*  SYNOPSIS
*
*  void glp_set_graph_name(glp_graph *G, const char *name);
*
*  DESCRIPTION
*
*  The routine glp_set_graph_name assigns a symbolic name specified by
*  the character string name (1 to 255 chars) to the graph.
*
*  If the parameter name is NULL or an empty string, the routine erases
*  the existing symbolic name of the graph. */

void glp_set_graph_name(glp_graph *G, const char *name)
{     if (G->name != NULL)
      {  dmp_free_atom(G->pool, G->name, strlen(G->name)+1);
         G->name = NULL;
      }
      if (!(name == NULL || name[0] == '\0'))
      {  int j;
         for (j = 0; name[j] != '\0'; j++)
         {  if (j == 256)
               xerror("glp_set_graph_name: graph name too long\n");
            if (iscntrl((unsigned char)name[j]))
               xerror("glp_set_graph_name: graph name contains invalid "
                  "character(s)\n");
         }
         G->name = dmp_get_atom(G->pool, strlen(name)+1);
         strcpy(G->name, name);
      }
      return;
}

/***********************************************************************
*  NAME
*
*  glp_add_vertices - add new vertices to graph
*
*  SYNOPSIS
*
*  int glp_add_vertices(glp_graph *G, int nadd);
*
*  DESCRIPTION
*
*  The routine glp_add_vertices adds nadd vertices to the specified
*  graph. New vertices are always added to the end of the vertex list,
*  so ordinal numbers of existing vertices remain unchanged.
*
*  Being added each new vertex is isolated (has no incident arcs).
*
*  RETURNS
*
*  The routine glp_add_vertices returns an ordinal number of the first
*  new vertex added to the graph. */

int glp_add_vertices(glp_graph *G, int nadd)
{     int i, nv_new;
      if (nadd < 1)
         xerror("glp_add_vertices: nadd = %d; invalid number of vertice"
            "s\n", nadd);
      if (nadd > NV_MAX - G->nv)
         xerror("glp_add_vertices: nadd = %d; too many vertices\n",
            nadd);
      /* determine new number of vertices */
      nv_new = G->nv + nadd;
      /* increase the room, if necessary */
      if (G->nv_max < nv_new)
      {  glp_vertex **save = G->v;
         while (G->nv_max < nv_new)
         {  G->nv_max += G->nv_max;
            xassert(G->nv_max > 0);
         }
         G->v = xcalloc(1+G->nv_max, sizeof(glp_vertex *));
         memcpy(&G->v[1], &save[1], G->nv * sizeof(glp_vertex *));
         xfree(save);
      }
      /* add new vertices to the end of the vertex list */
      for (i = G->nv+1; i <= nv_new; i++)
      {  glp_vertex *v;
         G->v[i] = v = dmp_get_atom(G->pool, sizeof(glp_vertex));
         v->i = i;
         v->name = NULL;
         v->entry = NULL;
         if (G->v_size == 0)
            v->data = NULL;
         else
         {  v->data = dmp_get_atom(G->pool, G->v_size);
            memset(v->data, 0, G->v_size);
         }
         v->temp = NULL;
         v->in = v->out = NULL;
      }
      /* set new number of vertices */
      G->nv = nv_new;
      /* return the ordinal number of the first vertex added */
      return nv_new - nadd + 1;
}

/**********************************************************************/

void glp_set_vertex_name(glp_graph *G, int i, const char *name)
{     /* assign (change) vertex name */
      glp_vertex *v;
      if (!(1 <= i && i <= G->nv))
         xerror("glp_set_vertex_name: i = %d; vertex number out of rang"
            "e\n", i);
      v = G->v[i];
      if (v->name != NULL)
      {  if (v->entry != NULL)
         {  xassert(G->index != NULL);
            avl_delete_node(G->index, v->entry);
            v->entry = NULL;
         }
         dmp_free_atom(G->pool, v->name, strlen(v->name)+1);
         v->name = NULL;
      }
      if (!(name == NULL || name[0] == '\0'))
      {  int k;
         for (k = 0; name[k] != '\0'; k++)
         {  if (k == 256)
               xerror("glp_set_vertex_name: i = %d; vertex name too lon"
                  "g\n", i);
            if (iscntrl((unsigned char)name[k]))
               xerror("glp_set_vertex_name: i = %d; vertex name contain"
                  "s invalid character(s)\n", i);
         }
         v->name = dmp_get_atom(G->pool, strlen(name)+1);
         strcpy(v->name, name);
         if (G->index != NULL)
         {  xassert(v->entry == NULL);
            v->entry = avl_insert_node(G->index, v->name);
            avl_set_node_link(v->entry, v);
         }
      }
      return;
}

/***********************************************************************
*  NAME
*
*  glp_add_arc - add new arc to graph
*
*  SYNOPSIS
*
*  glp_arc *glp_add_arc(glp_graph *G, int i, int j);
*
*  DESCRIPTION
*
*  The routine glp_add_arc adds a new arc to the specified graph.
*
*  The parameters i and j specify the ordinal numbers of, resp., tail
*  and head vertices of the arc. Note that self-loops and multiple arcs
*  are allowed.
*
*  RETURNS
*
*  The routine glp_add_arc returns a pointer to the arc added. */

glp_arc *glp_add_arc(glp_graph *G, int i, int j)
{     glp_arc *a;
      if (!(1 <= i && i <= G->nv))
         xerror("glp_add_arc: i = %d; tail vertex number out of range\n"
            , i);
      if (!(1 <= j && j <= G->nv))
         xerror("glp_add_arc: j = %d; head vertex number out of range\n"
            , j);
      if (G->na == NA_MAX)
         xerror("glp_add_arc: too many arcs\n");
      a = dmp_get_atom(G->pool, sizeof(glp_arc));
      a->tail = G->v[i];
      a->head = G->v[j];
      if (G->a_size == 0)
         a->data = NULL;
      else
      {  a->data = dmp_get_atom(G->pool, G->a_size);
         memset(a->data, 0, G->a_size);
      }
      a->temp = NULL;
      a->t_prev = NULL;
      a->t_next = G->v[i]->out;
      if (a->t_next != NULL) a->t_next->t_prev = a;
      a->h_prev = NULL;
      a->h_next = G->v[j]->in;
      if (a->h_next != NULL) a->h_next->h_prev = a;
      G->v[i]->out = G->v[j]->in = a;
      G->na++;
      return a;
}

/***********************************************************************
*  NAME
*
*  glp_del_vertices - delete vertices from graph
*
*  SYNOPSIS
*
*  void glp_del_vertices(glp_graph *G, int ndel, const int num[]);
*
*  DESCRIPTION
*
*  The routine glp_del_vertices deletes vertices along with all
*  incident arcs from the specified graph. Ordinal numbers of vertices
*  to be deleted should be placed in locations num[1], ..., num[ndel],
*  ndel > 0.
*
*  Note that deleting vertices involves changing ordinal numbers of
*  other vertices remaining in the graph. New ordinal numbers of the
*  remaining vertices are assigned under the assumption that the
*  original order of vertices is not changed. */

void glp_del_vertices(glp_graph *G, int ndel, const int num[])
{     glp_vertex *v;
      int i, k, nv_new;
      /* scan the list of vertices to be deleted */
      if (!(1 <= ndel && ndel <= G->nv))
         xerror("glp_del_vertices: ndel = %d; invalid number of vertice"
            "s\n", ndel);
      for (k = 1; k <= ndel; k++)
      {  /* take the number of vertex to be deleted */
         i = num[k];
         /* obtain pointer to i-th vertex */
         if (!(1 <= i && i <= G->nv))
            xerror("glp_del_vertices: num[%d] = %d; vertex number out o"
               "f range\n", k, i);
         v = G->v[i];
         /* check that the vertex is not marked yet */
         if (v->i == 0)
            xerror("glp_del_vertices: num[%d] = %d; duplicate vertex nu"
               "mbers not allowed\n", k, i);
         /* erase symbolic name assigned to the vertex */
         glp_set_vertex_name(G, i, NULL);
         xassert(v->name == NULL);
         xassert(v->entry == NULL);
         /* free vertex data, if allocated */
         if (v->data != NULL)
            dmp_free_atom(G->pool, v->data, G->v_size);
         /* delete all incoming arcs */
         while (v->in != NULL)
            glp_del_arc(G, v->in);
         /* delete all outgoing arcs */
         while (v->out != NULL)
            glp_del_arc(G, v->out);
         /* mark the vertex to be deleted */
         v->i = 0;
      }
      /* delete all marked vertices from the vertex list */
      nv_new = 0;
      for (i = 1; i <= G->nv; i++)
      {  /* obtain pointer to i-th vertex */
         v = G->v[i];
         /* check if the vertex is marked */
         if (v->i == 0)
         {  /* it is marked, delete it */
            dmp_free_atom(G->pool, v, sizeof(glp_vertex));
         }
         else
         {  /* it is not marked, keep it */
            v->i = ++nv_new;
            G->v[v->i] = v;
         }
      }
      /* set new number of vertices in the graph */
      G->nv = nv_new;
      return;
}

/***********************************************************************
*  NAME
*
*  glp_del_arc - delete arc from graph
*
*  SYNOPSIS
*
*  void glp_del_arc(glp_graph *G, glp_arc *a);
*
*  DESCRIPTION
*
*  The routine glp_del_arc deletes an arc from the specified graph.
*  The arc to be deleted must exist. */

void glp_del_arc(glp_graph *G, glp_arc *a)
{     /* some sanity checks */
      xassert(G->na > 0);
      xassert(1 <= a->tail->i && a->tail->i <= G->nv);
      xassert(a->tail == G->v[a->tail->i]);
      xassert(1 <= a->head->i && a->head->i <= G->nv);
      xassert(a->head == G->v[a->head->i]);
      /* remove the arc from the list of incoming arcs */
      if (a->h_prev == NULL)
         a->head->in = a->h_next;
      else
         a->h_prev->h_next = a->h_next;
      if (a->h_next == NULL)
         ;
      else
         a->h_next->h_prev = a->h_prev;
      /* remove the arc from the list of outgoing arcs */
      if (a->t_prev == NULL)
         a->tail->out = a->t_next;
      else
         a->t_prev->t_next = a->t_next;
      if (a->t_next == NULL)
         ;
      else
         a->t_next->t_prev = a->t_prev;
      /* free arc data, if allocated */
      if (a->data != NULL)
         dmp_free_atom(G->pool, a->data, G->a_size);
      /* delete the arc from the graph */
      dmp_free_atom(G->pool, a, sizeof(glp_arc));
      G->na--;
      return;
}

/***********************************************************************
*  NAME
*
*  glp_erase_graph - erase graph content
*
*  SYNOPSIS
*
*  void glp_erase_graph(glp_graph *G, int v_size, int a_size);
*
*  DESCRIPTION
*
*  The routine glp_erase_graph erases the content of the specified
*  graph. The effect of this operation is the same as if the graph
*  would be deleted with the routine glp_delete_graph and then created
*  anew with the routine glp_create_graph, with exception that the
*  handle (pointer) to the graph remains valid. */

static void delete_graph(glp_graph *G)
{     dmp_delete_pool(G->pool);
      xfree(G->v);
      if (G->index != NULL) avl_delete_tree(G->index);
      return;
}

void glp_erase_graph(glp_graph *G, int v_size, int a_size)
{     if (!(0 <= v_size && v_size <= 256))
         xerror("glp_erase_graph: v_size = %d; invalid size of vertex d"
            "ata\n", v_size);
      if (!(0 <= a_size && a_size <= 256))
         xerror("glp_erase_graph: a_size = %d; invalid size of arc data"
            "\n", a_size);
      delete_graph(G);
      create_graph(G, v_size, a_size);
      return;
}

/***********************************************************************
*  NAME
*
*  glp_delete_graph - delete graph
*
*  SYNOPSIS
*
*  void glp_delete_graph(glp_graph *G);
*
*  DESCRIPTION
*
*  The routine glp_delete_graph deletes the specified graph and frees
*  all the memory allocated to this program object. */

void glp_delete_graph(glp_graph *G)
{     delete_graph(G);
      xfree(G);
      return;
}

/**********************************************************************/

void glp_create_v_index(glp_graph *G)
{     /* create vertex name index */
      glp_vertex *v;
      int i;
      if (G->index == NULL)
      {  G->index = avl_create_tree(avl_strcmp, NULL);
         for (i = 1; i <= G->nv; i++)
         {  v = G->v[i];
            xassert(v->entry == NULL);
            if (v->name != NULL)
            {  v->entry = avl_insert_node(G->index, v->name);
               avl_set_node_link(v->entry, v);
            }
         }
      }
      return;
}

int glp_find_vertex(glp_graph *G, const char *name)
{     /* find vertex by its name */
      AVLNODE *node;
      int i = 0;
      if (G->index == NULL)
         xerror("glp_find_vertex: vertex name index does not exist\n");
      if (!(name == NULL || name[0] == '\0' || strlen(name) > 255))
      {  node = avl_find_node(G->index, name);
         if (node != NULL)
            i = ((glp_vertex *)avl_get_node_link(node))->i;
      }
      return i;
}

void glp_delete_v_index(glp_graph *G)
{     /* delete vertex name index */
      int i;
      if (G->index != NULL)
      {  avl_delete_tree(G->index), G->index = NULL;
         for (i = 1; i <= G->nv; i++) G->v[i]->entry = NULL;
      }
      return;
}

/* eof */