int
flatten (
struct vtx_data **graph, /* array of vtx data for graph */
int nvtxs, /* number of vertices in graph */
int nedges, /* number of edges in graph */
struct vtx_data ***pcgraph, /* coarsened version of graph */
int *pcnvtxs, /* number of vtxs in coarsened graph */
int *pcnedges, /* number of edges in coarsened graph */
int **pv2cv, /* pointer to v2cv */
int using_ewgts, /* are edge weights being used? */
int igeom, /* dimensions of geometric data */
float **coords, /* coordinates for vertices */
float **ccoords /* coordinates for coarsened vertices */
)
{
double Thresh; /* minimal acceptable size reduction */
int *v2cv; /* map from vtxs to coarse vtxs */
int cnvtxs; /* number of vertices in flattened graph */
void find_flat(), makefgraph();
Thresh = .9;
v2cv = smalloc((nvtxs + 1) * sizeof(int));
find_flat(graph, nvtxs, &cnvtxs, v2cv);
if (cnvtxs <= Thresh * nvtxs) { /* Sufficient shrinkage? */
makefgraph(graph, nvtxs, nedges, pcgraph, cnvtxs, pcnedges, v2cv,
using_ewgts, igeom, coords, ccoords);
*pcnvtxs = cnvtxs;
*pv2cv = v2cv;
return (TRUE);
}
else { /* Not worth bothering */
sfree(v2cv);
return (FALSE);
}
}
void
coarsen1 (
struct vtx_data **graph, /* array of vtx data for graph */
int nvtxs, /* number of vertices in graph */
int nedges, /* number of edges in graph */
struct vtx_data ***pcgraph, /* coarsened version of graph */
int *pcnvtxs, /* number of vtxs in coarsened graph */
int *pcnedges, /* number of edges in coarsened graph */
int **pv2cv, /* pointer to v2cv */
int igeom, /* dimension for geometric information */
float **coords, /* coordinates for vertices */
float **ccoords, /* coordinates for coarsened vertices */
int using_ewgts /* are edge weights being used? */
)
{
extern double coarsen_time;
extern double match_time;
double time; /* time routine is entered */
int *v2cv; /* maps from vtxs to cvtxs */
int *mflag; /* flag indicating vtx matched or not */
int cnvtxs; /* number of vtxs in coarse graph */
int nmerged; /* number of edges contracted */
double seconds();
int maxmatch();
void makev2cv(), makefgraph();
time = seconds();
/* Allocate and initialize space. */
v2cv = smalloc((nvtxs + 1) * sizeof(int));
mflag = smalloc((nvtxs + 1) * sizeof(int));
/* Find a maximal matching in the graph. */
nmerged = maxmatch(graph, nvtxs, nedges, mflag, using_ewgts, igeom, coords);
match_time += seconds() - time;
/* Now construct coarser graph by contracting along matching edges. */
/* Pairs of values in mflag array indicate matched vertices. */
/* A zero value indicates that vertex is unmatched. */
/*
makecgraph(graph, nvtxs, pcgraph, pcnvtxs, pcnedges, mflag,
*pv2cv, nmerged, using_ewgts, igeom, coords, ccoords);
makecgraph2(graph, nvtxs, nedges, pcgraph, pcnvtxs, pcnedges, mflag,
*pv2cv, nmerged, using_ewgts, igeom, coords, ccoords);
*/
makev2cv(mflag, nvtxs, v2cv);
sfree(mflag);
cnvtxs = nvtxs - nmerged;
makefgraph(graph, nvtxs, nedges, pcgraph, cnvtxs, pcnedges, v2cv,
using_ewgts, igeom, coords, ccoords);
*pcnvtxs = cnvtxs;
*pv2cv = v2cv;
coarsen_time += seconds() - time;
}
