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/* -*- mode: C -*- */
/* vim:set ts=4 sw=4 sts=4 et: */
/*
IGraph library.
Copyright (C) 2011-2012 Gabor Csardi <csardi.gabor@gmail.com>
334 Harvard street, Cambridge, MA 02139 USA
This program 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 2 of the License, or
(at your option) any later version.
This program 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 this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA
*/
#include "igraph_paths.h"
#include "igraph_datatype.h"
#include "igraph_dqueue.h"
#include "igraph_iterators.h"
#include "igraph_interrupt_internal.h"
#include "igraph_vector.h"
#include "igraph_interface.h"
#include "igraph_adjlist.h"
static int igraph_i_eccentricity(const igraph_t *graph,
igraph_vector_t *res,
igraph_vs_t vids,
igraph_neimode_t mode,
const igraph_adjlist_t *adjlist) {
int no_of_nodes = igraph_vcount(graph);
igraph_dqueue_long_t q;
igraph_vit_t vit;
igraph_vector_int_t counted;
int i, mark = 1;
igraph_vector_t vneis;
igraph_vector_int_t *neis;
IGRAPH_CHECK(igraph_dqueue_long_init(&q, 100));
IGRAPH_FINALLY(igraph_dqueue_long_destroy, &q);
IGRAPH_CHECK(igraph_vit_create(graph, vids, &vit));
IGRAPH_FINALLY(igraph_vit_destroy, &vit);
IGRAPH_CHECK(igraph_vector_int_init(&counted, no_of_nodes));
IGRAPH_FINALLY(igraph_vector_int_destroy, &counted);
if (!adjlist) {
IGRAPH_VECTOR_INIT_FINALLY(&vneis, 0);
}
IGRAPH_CHECK(igraph_vector_resize(res, IGRAPH_VIT_SIZE(vit)));
igraph_vector_fill(res, -1);
for (i = 0, IGRAPH_VIT_RESET(vit);
!IGRAPH_VIT_END(vit);
IGRAPH_VIT_NEXT(vit), mark++, i++) {
long int source;
source = IGRAPH_VIT_GET(vit);
IGRAPH_CHECK(igraph_dqueue_long_push(&q, source));
IGRAPH_CHECK(igraph_dqueue_long_push(&q, 0));
VECTOR(counted)[source] = mark;
IGRAPH_ALLOW_INTERRUPTION();
while (!igraph_dqueue_long_empty(&q)) {
long int act = igraph_dqueue_long_pop(&q);
long int dist = igraph_dqueue_long_pop(&q);
int j, n;
if (dist > VECTOR(*res)[i]) {
VECTOR(*res)[i] = dist;
}
if (adjlist) {
neis = igraph_adjlist_get(adjlist, act);
n = (int) igraph_vector_int_size(neis);
for (j = 0; j < n; j++) {
int nei = (int) VECTOR(*neis)[j];
if (VECTOR(counted)[nei] != mark) {
VECTOR(counted)[nei] = mark;
IGRAPH_CHECK(igraph_dqueue_long_push(&q, nei));
IGRAPH_CHECK(igraph_dqueue_long_push(&q, dist + 1));
}
}
} else {
IGRAPH_CHECK(igraph_neighbors(graph, &vneis,
(igraph_integer_t) act, mode));
n = (int) igraph_vector_size(&vneis);
for (j = 0; j < n; j++) {
int nei = (int) VECTOR(vneis)[j];
if (VECTOR(counted)[nei] != mark) {
VECTOR(counted)[nei] = mark;
IGRAPH_CHECK(igraph_dqueue_long_push(&q, nei));
IGRAPH_CHECK(igraph_dqueue_long_push(&q, dist + 1));
}
}
}
} /* while !igraph_dqueue_long_empty(dqueue) */
} /* for IGRAPH_VIT_NEXT(vit) */
if (!adjlist) {
igraph_vector_destroy(&vneis);
IGRAPH_FINALLY_CLEAN(1);
}
igraph_vector_int_destroy(&counted);
igraph_vit_destroy(&vit);
igraph_dqueue_long_destroy(&q);
IGRAPH_FINALLY_CLEAN(3);
return 0;
}
/**
* \function igraph_eccentricity
* Eccentricity of some vertices
*
* The eccentricity of a vertex is calculated by measuring the shortest
* distance from (or to) the vertex, to (or from) all vertices in the
* graph, and taking the maximum.
*
* </para><para>
* This implementation ignores vertex pairs that are in different
* components. Isolated vertices have eccentricity zero.
*
* \param graph The input graph, it can be directed or undirected.
* \param res Pointer to an initialized vector, the result is stored
* here.
* \param vids The vertices for which the eccentricity is calculated.
* \param mode What kind of paths to consider for the calculation:
* \c IGRAPH_OUT, paths that follow edge directions;
* \c IGRAPH_IN, paths that follow the opposite directions; and
* \c IGRAPH_ALL, paths that ignore edge directions. This argument
* is ignored for undirected graphs.
* \return Error code.
*
* Time complexity: O(v*(|V|+|E|)), where |V| is the number of
* vertices, |E| is the number of edges and v is the number of
* vertices for which eccentricity is calculated.
*
* \sa \ref igraph_radius().
*
* \example examples/simple/igraph_eccentricity.c
*/
int igraph_eccentricity(const igraph_t *graph,
igraph_vector_t *res,
igraph_vs_t vids,
igraph_neimode_t mode) {
return igraph_i_eccentricity(graph, res, vids, mode, /*adjlist=*/ 0);
}
/**
* \function igraph_radius
* Radius of a graph
*
* The radius of a graph is the defined as the minimum eccentricity of
* its vertices, see \ref igraph_eccentricity().
*
* \param graph The input graph, it can be directed or undirected.
* \param radius Pointer to a real variable, the result is stored
* here.
* \param mode What kind of paths to consider for the calculation:
* \c IGRAPH_OUT, paths that follow edge directions;
* \c IGRAPH_IN, paths that follow the opposite directions; and
* \c IGRAPH_ALL, paths that ignore edge directions. This argument
* is ignored for undirected graphs.
* \return Error code.
*
* Time complexity: O(|V|(|V|+|E|)), where |V| is the number of
* vertices and |E| is the number of edges.
*
* \sa \ref igraph_eccentricity().
*
* \example examples/simple/igraph_radius.c
*/
int igraph_radius(const igraph_t *graph, igraph_real_t *radius,
igraph_neimode_t mode) {
int no_of_nodes = igraph_vcount(graph);
if (no_of_nodes == 0) {
*radius = IGRAPH_NAN;
} else {
igraph_adjlist_t adjlist;
igraph_vector_t ecc;
IGRAPH_CHECK(igraph_adjlist_init(graph, &adjlist, mode));
IGRAPH_FINALLY(igraph_adjlist_destroy, &adjlist);
IGRAPH_VECTOR_INIT_FINALLY(&ecc, igraph_vcount(graph));
IGRAPH_CHECK(igraph_i_eccentricity(graph, &ecc, igraph_vss_all(),
mode, &adjlist));
*radius = igraph_vector_min(&ecc);
igraph_vector_destroy(&ecc);
igraph_adjlist_destroy(&adjlist);
IGRAPH_FINALLY_CLEAN(2);
}
return 0;
}
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