int main() {
igraph_t g;
long int i;
igraph_integer_t size;
/* DIRECTED */
igraph_star(&g, 10, IGRAPH_STAR_OUT, 0);
for (i=0; i<100; i++) {
igraph_es_t es;
igraph_eit_t it;
igraph_es_pairs_small(&es, IGRAPH_DIRECTED,
0,1,0,2,0,5,0,2,0,3,0,4,0,7,0,9, -1);
igraph_eit_create(&g, es, &it);
igraph_es_size(&g, &es, &size);
IGRAPH_EIT_RESET(it);
while (!IGRAPH_EIT_END(it)) {
IGRAPH_EIT_GET(it);
IGRAPH_EIT_NEXT(it);
size--;
}
if (size != 0) return 1;
igraph_eit_destroy(&it);
igraph_es_destroy(&es);
}
igraph_destroy(&g);
/* UNDIRECTED */
igraph_star(&g, 10, IGRAPH_STAR_UNDIRECTED, 0);
for (i=0; i<100; i++) {
igraph_es_t es;
igraph_eit_t it;
igraph_es_pairs_small(&es, IGRAPH_DIRECTED,
0,1,2,0,5,0,0,2,3,0,0,4,7,0,0,9, -1);
igraph_eit_create(&g, es, &it);
IGRAPH_EIT_RESET(it);
while (!IGRAPH_EIT_END(it)) {
IGRAPH_EIT_GET(it);
IGRAPH_EIT_NEXT(it);
}
igraph_eit_destroy(&it);
igraph_es_destroy(&es);
}
igraph_destroy(&g);
return 0;
}
igraph_vector_t * ggen_analyze_longest_antichain(igraph_t *g)
{
/* The following steps are implemented :
* - Convert our DAG to a specific bipartite graph B
* - solve maximum matching on B
* - conver maximum matching to min vectex cover
* - convert min vertex cover to antichain on G
*/
int err;
unsigned long i,vg,found,added;
igraph_t b,gstar;
igraph_vector_t edges,*res = NULL;
igraph_vector_t c,s,t,todo,n,next,l,r;
igraph_eit_t eit;
igraph_es_t es;
igraph_integer_t from,to;
igraph_vit_t vit;
igraph_vs_t vs;
igraph_real_t value;
if(g == NULL)
return NULL;
/* before creating the bipartite graph, we need all relations
* between any two vertices : the transitive closure of g */
err = igraph_copy(&gstar,g);
if(err) return NULL;
err = ggen_transform_transitive_closure(&gstar);
if(err) goto error;
/* Bipartite convertion : let G = (S,C),
* we build B = (U,V,E) with
* - U = V = S (each vertex is present twice)
* - (u,v) \in E iff :
* - u \in U
* - v \in V
* - u < v in C (warning, this means that we take
* transitive closure into account, not just the
* original edges)
* We will also need two additional nodes further in the code.
*/
vg = igraph_vcount(g);
err = igraph_empty(&b,vg*2,1);
if(err) goto error;
/* id and id+vg will be a vertex in U and its copy in V,
* iterate over gstar edges to create edges in b
*/
err = igraph_vector_init(&edges,igraph_ecount(&gstar));
if(err) goto d_b;
igraph_vector_clear(&edges);
err = igraph_eit_create(&gstar,igraph_ess_all(IGRAPH_EDGEORDER_ID),&eit);
if(err) goto d_edges;
for(IGRAPH_EIT_RESET(eit); !IGRAPH_EIT_END(eit); IGRAPH_EIT_NEXT(eit))
{
err = igraph_edge(&gstar,IGRAPH_EIT_GET(eit),&from,&to);
if(err)
{
igraph_eit_destroy(&eit);
goto d_edges;
}
to += vg;
igraph_vector_push_back(&edges,(igraph_real_t)from);
igraph_vector_push_back(&edges,(igraph_real_t)to);
}
igraph_eit_destroy(&eit);
err = igraph_add_edges(&b,&edges,NULL);
if(err) goto d_edges;
/* maximum matching on b */
igraph_vector_clear(&edges);
err = bipartite_maximum_matching(&b,&edges);
if(err) goto d_edges;
/* Let M be the max matching, and N be E - M
* Define T as all unmatched vectices from U as well as all vertices
* reachable from those by going left-to-right along N and right-to-left along
* M.
* Define L = U - T, R = V \inter T
* C:= L + R
* C is a minimum vertex cover
*/
err = igraph_vector_init_seq(&n,0,igraph_ecount(&b)-1);
if(err) goto d_edges;
err = vector_diff(&n,&edges);
if(err) goto d_n;
err = igraph_vector_init(&c,vg);
if(err) goto d_n;
igraph_vector_clear(&c);
/* matched vertices : S */
err = igraph_vector_init(&s,vg);
if(err) goto d_c;
igraph_vector_clear(&s);
for(i = 0; i < igraph_vector_size(&edges); i++)
{
err = igraph_edge(&b,VECTOR(edges)[i],&from,&to);
if(err) goto d_s;
igraph_vector_push_back(&s,from);
}
/* we may have inserted the same vertex multiple times */
err = vector_uniq(&s);
if(err) goto d_s;
/* unmatched */
err = igraph_vector_init_seq(&t,0,vg-1);
if(err) goto d_s;
err = vector_diff(&t,&s);
if(err) goto d_t;
/* alternating paths
*/
err = igraph_vector_copy(&todo,&t);
if(err) goto d_t;
err = igraph_vector_init(&next,vg);
if(err) goto d_todo;
igraph_vector_clear(&next);
do {
vector_uniq(&todo);
added = 0;
for(i = 0; i < igraph_vector_size(&todo); i++)
{
if(VECTOR(todo)[i] < vg)
{
/* scan edges */
err = igraph_es_adj(&es,VECTOR(todo)[i],IGRAPH_OUT);
if(err) goto d_next;
err = igraph_eit_create(&b,es,&eit);
if(err)
{
igraph_es_destroy(&es);
goto d_next;
}
for(IGRAPH_EIT_RESET(eit); !IGRAPH_EIT_END(eit); IGRAPH_EIT_NEXT(eit))
{
if(igraph_vector_binsearch(&n,IGRAPH_EIT_GET(eit),NULL))
{
err = igraph_edge(&b,IGRAPH_EIT_GET(eit),&from,&to);
if(err)
{
igraph_eit_destroy(&eit);
igraph_es_destroy(&es);
goto d_next;
}
if(!igraph_vector_binsearch(&t,to,NULL))
{
igraph_vector_push_back(&next,to);
added = 1;
}
}
}
}
else
{
/* scan edges */
err = igraph_es_adj(&es,VECTOR(todo)[i],IGRAPH_IN);
if(err) goto d_next;
err = igraph_eit_create(&b,es,&eit);
if(err)
{
igraph_es_destroy(&es);
goto d_next;
}
for(IGRAPH_EIT_RESET(eit); !IGRAPH_EIT_END(eit); IGRAPH_EIT_NEXT(eit))
{
if(igraph_vector_binsearch(&edges,IGRAPH_EIT_GET(eit),NULL))
{
err = igraph_edge(&b,IGRAPH_EIT_GET(eit),&from,&to);
if(err)
{
igraph_eit_destroy(&eit);
igraph_es_destroy(&es);
goto d_next;
}
if(!igraph_vector_binsearch(&t,to,NULL))
{
igraph_vector_push_back(&next,from);
added = 1;
}
}
}
}
igraph_es_destroy(&es);
igraph_eit_destroy(&eit);
}
igraph_vector_append(&t,&todo);
igraph_vector_clear(&todo);
igraph_vector_append(&todo,&next);
igraph_vector_clear(&next);
} while(added);
err = igraph_vector_init_seq(&l,0,vg-1);
if(err) goto d_t;
err = vector_diff(&l,&t);
if(err) goto d_l;
err = igraph_vector_update(&c,&l);
if(err) goto d_l;
err = igraph_vector_init(&r,vg);
if(err) goto d_l;
igraph_vector_clear(&r);
/* compute V \inter T */
for(i = 0; i < igraph_vector_size(&t); i++)
{
if(VECTOR(t)[i] >= vg)
igraph_vector_push_back(&r,VECTOR(t)[i]);
}
igraph_vector_add_constant(&r,(igraph_real_t)-vg);
err = vector_union(&c,&r);
if(err) goto d_r;
/* our antichain is U - C */
res = malloc(sizeof(igraph_vector_t));
if(res == NULL) goto d_r;
err = igraph_vector_init_seq(res,0,vg-1);
if(err) goto f_res;
err = vector_diff(res,&c);
if(err) goto d_res;
goto ret;
d_res:
igraph_vector_destroy(res);
f_res:
free(res);
res = NULL;
ret:
d_r:
igraph_vector_destroy(&r);
d_l:
igraph_vector_destroy(&l);
d_next:
igraph_vector_destroy(&next);
d_todo:
igraph_vector_destroy(&todo);
d_t:
igraph_vector_destroy(&t);
d_s:
igraph_vector_destroy(&s);
d_c:
igraph_vector_destroy(&c);
d_n:
igraph_vector_destroy(&n);
d_edges:
igraph_vector_destroy(&edges);
d_b:
igraph_destroy(&b);
error:
igraph_destroy(&gstar);
return res;
}
int ggen_write_graph(igraph_t *g, FILE *output)
{
Agraph_t *cg;
Agnode_t *f,*t;
Agedge_t *edge;
igraph_vector_ptr_t vertices;
igraph_eit_t eit;
int err;
unsigned long i,j;
unsigned long vcount = igraph_vcount(g);
igraph_integer_t from,to;
char name[GGEN_DEFAULT_NAME_SIZE];
char *str = NULL;
igraph_strvector_t gnames,vnames,enames;
igraph_vector_t gtypes,vtypes,etypes;
Agsym_t *attr;
/* see warning below */
igraph_error_handler_t *error_handler;
err = igraph_vector_ptr_init(&vertices,vcount);
if(err) return 1;
/* WARNING: this should be changed if igraph-0.6 gets
* stable.
* We need to ignore some igraph_cattribute errors
* because we try to retrieve special attributes (ggen specifics).
* igraph version 0.6 include a cattribute_has_attr that should be
* used instead of ignoring errors.
*/
error_handler = igraph_set_error_handler(igraph_error_handler_ignore);
/* open graph
* its name is saved in __ggen_graph_name if it exists
*/
str =(char *) GAS(g,GGEN_GRAPH_NAME_ATTR);
if(!str)
cg = agopen(GGEN_DEFAULT_GRAPH_NAME,Agdirected,NULL);
else
cg = agopen(str,Agdirected,NULL);
if(!cg)
{
err = 1;
goto d_v;
}
/* save a pointer to each vertex */
for(i = 0; i < vcount; i++)
{
/* find a vertex name */
str = vid2vname_unsafe(name,g,i);
if(!str)
f = agnode(cg,name,1);
else
f = agnode(cg,str,1);
VECTOR(vertices)[i] = (void *)f;
}
/* We have finished with dangerous attributes accesses */
igraph_set_error_handler(error_handler);
/* now loop through edges in the igraph */
err = igraph_eit_create(g,igraph_ess_all(IGRAPH_EDGEORDER_ID),&eit);
if(err) goto c_ag;
for(IGRAPH_EIT_RESET(eit); !IGRAPH_EIT_END(eit); IGRAPH_EIT_NEXT(eit))
{
err = igraph_edge(g,IGRAPH_EIT_GET(eit),&from,&to);
if(err) goto d_eit;
f = (Agnode_t *) VECTOR(vertices)[(unsigned long)from];
t = (Agnode_t *) VECTOR(vertices)[(unsigned long)to];
agedge(cg,f,t,NULL,1);
}
/* find all properties */
igraph_strvector_init(&gnames,1);
igraph_strvector_init(&vnames,vcount);
igraph_strvector_init(&enames,igraph_ecount(g));
igraph_vector_init(>ypes,1);
igraph_vector_init(&vtypes,vcount);
igraph_vector_init(&etypes,igraph_ecount(g));
err = igraph_cattribute_list(g,&gnames,>ypes,&vnames,&vtypes,&enames,&etypes);
if(err) goto d_eit;
/* add graph properties */
for(i = 0; i < igraph_strvector_size(&gnames); i++)
{
if(strcmp(GGEN_GRAPH_NAME_ATTR,STR(gnames,i)))
{
if(VECTOR(gtypes)[i]==IGRAPH_ATTRIBUTE_NUMERIC) {
snprintf(name,GGEN_DEFAULT_NAME_SIZE,"%f",
(double)GAN(g,STR(gnames,i)));
agattr(cg,AGRAPH,(char *)STR(gnames,i),name);
}
else
agattr(cg,AGRAPH,(char *)STR(gnames,i),
(char *)GAS(g,STR(gnames,i)));
}
}
/* add vertex properties */
for(i = 0; i < igraph_strvector_size(&vnames); i++)
{
if(strcmp(GGEN_VERTEX_NAME_ATTR,STR(vnames,i)))
{
/* creates the attribute but we still need to set it for each vertex */
attr = agattr(cg,AGNODE,(char *)STR(vnames,i),GGEN_CGRAPH_DEFAULT_VALUE);
for(j = 0; j < vcount; j++)
{
f = (Agnode_t *) VECTOR(vertices)[j];
if(VECTOR(vtypes)[i]==IGRAPH_ATTRIBUTE_NUMERIC) {
snprintf(name,GGEN_DEFAULT_NAME_SIZE,"%f",
(double)VAN(g,STR(vnames,i),j));
agxset(f,attr,name);
}
else
agxset(f,attr,(char *)VAS(g,STR(vnames,i),j));
}
}
}
/* add edges properties */
for(i = 0; i < igraph_strvector_size(&enames); i++)
{
/* creates the attribute but we still need to set it for each edge */
attr = agattr(cg,AGEDGE,(char *)STR(enames,i),GGEN_CGRAPH_DEFAULT_VALUE);
for(j = 0; j < igraph_ecount(g); j++)
{
igraph_edge(g,j,&from,&to);
f = (Agnode_t *) VECTOR(vertices)[(unsigned long)from];
t = (Agnode_t *) VECTOR(vertices)[(unsigned long)to];
edge = agedge(cg,f,t,NULL,0);
if(VECTOR(etypes)[i]==IGRAPH_ATTRIBUTE_NUMERIC) {
snprintf(name,GGEN_DEFAULT_NAME_SIZE,"%f",
(double)EAN(g,STR(enames,i),j));
agxset(edge,attr,name);
}
else
agxset(edge,attr,(char *)EAS(g,STR(enames,i),j));
}
}
/* write the graph */
err = agwrite(cg,(void *)output);
d_eit:
igraph_eit_destroy(&eit);
c_ag:
agclose(cg);
d_v:
igraph_vector_ptr_destroy(&vertices);
return err;
}
/**
* \ingroup interface
* \function igraph_delete_edges
* \brief Removes edges from a graph.
*
* </para><para>
* The edges to remove are given as an edge selector.
*
* </para><para>
* This function cannot remove vertices, they will be kept, even if
* they lose all their edges.
*
* </para><para>
* This function invalidates all iterators.
* \param graph The graph to work on.
* \param edges The edges to remove.
* \return Error code.
*
* Time complexity: O(|V|+|E|) where
* |V|
* and |E| are the number of vertices
* and edges in the \em original graph, respectively.
*/
int igraph_delete_edges(igraph_t *graph, igraph_es_t edges) {
long int no_of_edges=igraph_ecount(graph);
long int no_of_nodes=igraph_vcount(graph);
long int edges_to_remove=0;
long int remaining_edges;
igraph_eit_t eit;
igraph_vector_t newfrom, newto, newoi;
int *mark;
long int i, j;
mark=igraph_Calloc(no_of_edges, int);
if (mark==0) {
IGRAPH_ERROR("Cannot delete edges", IGRAPH_ENOMEM);
}
IGRAPH_FINALLY(igraph_free, mark);
IGRAPH_CHECK(igraph_eit_create(graph, edges, &eit));
IGRAPH_FINALLY(igraph_eit_destroy, &eit);
for (IGRAPH_EIT_RESET(eit); !IGRAPH_EIT_END(eit); IGRAPH_EIT_NEXT(eit)) {
long int e=IGRAPH_EIT_GET(eit);
if (mark[e]==0) {
edges_to_remove++;
mark[e]++;
}
}
remaining_edges=no_of_edges-edges_to_remove;
/* We don't need the iterator any more */
igraph_eit_destroy(&eit);
IGRAPH_FINALLY_CLEAN(1);
IGRAPH_VECTOR_INIT_FINALLY(&newfrom, remaining_edges);
IGRAPH_VECTOR_INIT_FINALLY(&newto, remaining_edges);
/* Actually remove the edges, move from pos i to pos j in newfrom/newto */
for (i=0,j=0; j<remaining_edges; i++) {
if (mark[i]==0) {
VECTOR(newfrom)[j] = VECTOR(graph->from)[i];
VECTOR(newto)[j] = VECTOR(graph->to)[i];
j++;
}
}
/* Create index, this might require additional memory */
IGRAPH_VECTOR_INIT_FINALLY(&newoi, remaining_edges);
IGRAPH_CHECK(igraph_vector_order(&newfrom, &newto, &newoi, no_of_nodes));
IGRAPH_CHECK(igraph_vector_order(&newto, &newfrom, &graph->ii, no_of_nodes));
/* Attributes, we use the original from vector to create an index,
needed for the attribute handler. This index is the same as the
one used for copying the edges of course The attribute handler is
safe, never returns error. */
if (graph->attr) {
long int i, j=1;
for (i=0; i<igraph_vector_size(&graph->from); i++) {
if (mark[i] == 0) {
VECTOR(graph->from)[i]=j++;
} else {
VECTOR(graph->from)[i]=0;
}
}
igraph_i_attribute_delete_edges(graph, &graph->from);
}
/* Ok, we've all memory needed, free the old structure */
igraph_vector_destroy(&graph->from);
igraph_vector_destroy(&graph->to);
igraph_vector_destroy(&graph->oi);
graph->from=newfrom;
graph->to=newto;
graph->oi=newoi;
IGRAPH_FINALLY_CLEAN(3);
igraph_Free(mark);
IGRAPH_FINALLY_CLEAN(1);
/* Create start vectors, no memory is needed for this */
igraph_i_create_start(&graph->os, &graph->from, &graph->oi, no_of_nodes);
igraph_i_create_start(&graph->is, &graph->to, &graph->ii, no_of_nodes);
/* Nothing to deallocate... */
return 0;
}
void EdgeIterator::reset() { IGRAPH_EIT_RESET(eit()); }
