public static bool is_an_edge(vtx_data *vertex, /* data for a vertex */
int v2, /* neighbor to look for */
float *weight2 /* weight of edge if found */
)
{
int i; /* loop counter */
for (i = 1; i < vertex->nedges; i++)
{
// ReSharper disable once InvertIf
if (vertex->edges[i] == v2)
{
if (vertex->ewgts != null)
{
*weight2 = vertex->ewgts[i];
}
else
{
*weight2 = 1;
}
return(true);
}
}
return(false);
}
/* Change from a FORTRAN graph style to our graph data structure. */
public static bool reformat(int *start, /* start of edge list for each vertex */
int *adjacency, /* edge list data */
int nvtxs, /* number of vertices in graph */
int *pnedges, /* ptr to number of edges in graph */
int *vwgts, /* weights for all vertices */
float *ewgts, /* weights for all edges */
vtx_data ***pgraph /* ptr to array of vtx data for graph */
)
{
Trace.WriteLine($"<Entering {nameof(reformat)}>");
vtx_data **graph = null; /* array of vtx data for graph */
vtx_data * links = null; /* space for data for all vtxs */
int * edges = null; /* space for all adjacency lists */
float * eweights = null; /* space for all edge weights */
int * eptr = null; /* steps through adjacency list */
int * eptr_save = null; /* saved index into adjacency list */
float * wptr = null; /* steps through edge weights list */
int self_edge; /* number of self loops detected */
int size; /* length of all edge lists */
double sum; /* sum of edge weights for a vtx */
int i, j; /* loop counters */
var useEdgeWeights = (ewgts != null); /* are edge weights being used? */
var using_vwgts = (vwgts != null); /* are vertex weights being used? */
graph = (vtx_data **)Marshal.AllocHGlobal((nvtxs + 1) * sizeof(vtx_data *));
*pgraph = graph;
if (graph == null)
{
return(true);
}
graph[1] = null;
/* Set up all the basic data structure for the vertices. */
/* Replace many small mallocs by a few large ones. */
links = (vtx_data *)Marshal.AllocHGlobal((nvtxs) * sizeof(vtx_data));
if (links == null)
{
return(true);
}
for (i = 1; i <= nvtxs; i++)
{
graph[i] = links++;
}
graph[1]->edges = null;
graph[1]->ewgts = null;
/* Now fill in all the data fields. */
if (start != null)
{
*pnedges = start[nvtxs] / 2;
}
else
{
*pnedges = 0;
}
size = 2 * (*pnedges) + nvtxs;
edges = (int *)Marshal.AllocHGlobal(size * sizeof(int));
if (edges == null)
{
return(true);
}
if (useEdgeWeights)
{
eweights = (float *)Marshal.AllocHGlobal(size * sizeof(float));
if (eweights == null)
{
return(true);
}
}
if (start != null)
{
eptr = adjacency + start[0];
wptr = ewgts;
}
self_edge = 0;
for (i = 1; i <= nvtxs; i++)
{
if (using_vwgts)
{
graph[i]->vwgt = *(vwgts++);
}
else
{
graph[i]->vwgt = 1;
}
if (start != null)
{
size = start[i] - start[i - 1];
}
else
{
size = 0;
}
graph[i]->nedges = size + 1;
graph[i]->edges = edges;
*edges++ = i;
eptr_save = eptr;
for (j = size; j != 0; j--)
{
if (*eptr != i)
{
*edges++ = *eptr++;
}
else
{
/* Self edge, skip it. */
//if (self_edge == 0)
{
Trace.WriteLine($"WARNING: Self edge ({i:d},{i:d}) being ignored");
}
++self_edge;
eptr++;
--(graph[i]->nedges);
--(*pnedges);
}
}
if (useEdgeWeights)
{
graph[i]->ewgts = eweights;
eweights++;
sum = 0;
for (j = size; j != 0; j--)
{
if (*eptr_save++ != i)
{
sum += *wptr;
*eweights++ = *wptr++;
}
else
{
wptr++;
}
}
graph[i]->ewgts[0] = (float)-sum;
}
else
{
graph[i]->ewgts = null;
}
}
if (self_edge > 1)
{
Trace.WriteLine($"WARNING: {self_edge:d} self edges were detected and ignored");
}
return(false);
}
public static void makefgraph(vtx_data **graph, /* array of vtx data for graph */
int nvtxs, /* number of vertices in graph */
int nedges, /* number of edges in graph */
vtx_data ***pcgraph, /* coarsened version of graph */
int cnvtxs, /* number of vtxs in coarsened graph */
int *pcnedges, /* number of edges in coarsened graph */
int *v2cv, /* mapping from vtxs to coarsened vtxs */
bool useEdgeWeights, /* are edge weights being used? */
int igeom, /* dimensions of geometric data */
float **coords, /* coordinates for vertices */
float **ccoords /* coordinates for coarsened vertices */
)
{
vtx_data **cgraph = null; /* coarsened version of graph */
vtx_data * links = null; /* space for all the vertex data */
vtx_data **gptr = null; /* loops through cgraph */
vtx_data * cgptr = null; /* loops through cgraph */
int * iptr = null; /* loops through integer arrays */
int * seenflag = null; /* flags for vtxs already put in edge list */
int * sptr = null; /* loops through seenflags */
int * cv2v_vals = null; /* vtxs corresponding to each cvtx */
int * cv2v_ptrs = null; /* indices into cv2v_vals */
float * eweights = null; /* space for edge weights in coarsened graph */
float * ewptr = null; /* loops through eweights */
float * fptr = null; /* loops through eweights */
float ewgt; /* edge weight */
double ewgt_sum; /* sum of edge weights */
double time; /* timing parameters */
int nseen; /* number of edges of coarse graph seen so far */
int vtx; /* vertex in original graph */
int cvtx; /* vertex in coarse graph */
int cnedges; /* twice number of edges in coarsened graph */
int neighbor; /* neighboring vertex */
int size; /* space needed for coarsened graph */
int * edges = null; /* space for edges in coarsened graph */
int * eptr = null; /* loops through edges data structure */
int cneighbor; /* neighboring vertex number in coarsened graph */
int i, j; /* loop counters */
/* Compute the number of vertices and edges in the coarsened graph, */
/* and construct start pointers into coarsened edge array. */
time = seconds();
/* Construct mapping from original graph vtxs to coarsened graph vtxs. */
cv2v_vals = (int *)Marshal.AllocHGlobal(nvtxs * sizeof(int));
cv2v_ptrs = (int *)Marshal.AllocHGlobal((cnvtxs + 2) * sizeof(int));
makecv2v(nvtxs, cnvtxs, v2cv, cv2v_vals, cv2v_ptrs);
/* Compute an upper bound on the number of coarse graph edges. */
cnedges = nedges - (nvtxs - cnvtxs);
/* Now allocate space for the new graph. Overallocate and realloc later. */
*pcgraph = cgraph = (vtx_data **)Marshal.AllocHGlobal((cnvtxs + 1) * sizeof(vtx_data *));
links = (vtx_data *)Marshal.AllocHGlobal(cnvtxs * sizeof(vtx_data));
size = 2 * cnedges + cnvtxs;
edges = (int *)Marshal.AllocHGlobal(size * sizeof(int));
if (COARSEN_EWGTS)
{
ewptr = eweights = (float *)Marshal.AllocHGlobal(size * sizeof(float));
}
/* Zero all the seen flags. */
seenflag = (int *)Marshal.AllocHGlobal((cnvtxs + 1) * sizeof(int));
sptr = seenflag;
for (i = cnvtxs; i != 0; i--)
{
*(++sptr) = 0;
}
/* Use the renumbering to fill in the edge lists for the new graph. */
cnedges = 0;
eptr = edges;
ewgt = 1;
sptr = cv2v_vals;
for (cvtx = 1; cvtx <= cnvtxs; cvtx++)
{
nseen = 1;
cgptr = cgraph[cvtx] = links++;
if (COARSEN_VWGTS)
{
cgptr->vwgt = 0;
}
else
{
cgptr->vwgt = 1;
}
eptr[0] = cvtx;
cgptr->edges = eptr;
if (COARSEN_EWGTS)
{
cgptr->ewgts = ewptr;
}
else
{
cgptr->ewgts = null;
}
ewgt_sum = 0;
for (i = cv2v_ptrs[cvtx + 1] - cv2v_ptrs[cvtx]; i != 0; i--)
{
vtx = *sptr++;
iptr = graph[vtx]->edges;
if (useEdgeWeights)
{
fptr = graph[vtx]->ewgts;
}
for (j = graph[vtx]->nedges - 1; j != 0; j--)
{
neighbor = *(++iptr);
cneighbor = v2cv[neighbor];
if (cneighbor != cvtx)
{
if (useEdgeWeights)
{
ewgt = *(++fptr);
}
ewgt_sum += ewgt;
/* Seenflags being used as map from cvtx to index. */
if (seenflag[cneighbor] == 0)
{
/* New neighbor. */
cgptr->edges[nseen] = cneighbor;
if (COARSEN_EWGTS)
{
cgptr->ewgts[nseen] = ewgt;
}
seenflag[cneighbor] = nseen++;
}
else
{
/* Already seen neighbor. */
if (COARSEN_EWGTS)
{
cgptr->ewgts[seenflag[cneighbor]] += ewgt;
}
}
}
else if (useEdgeWeights)
{
++fptr;
}
}
}
/* Now clear the seenflag values. */
iptr = cgptr->edges;
for (j = nseen - 1; j != 0; j--)
{
seenflag[*(++iptr)] = 0;
}
if (COARSEN_EWGTS)
{
cgptr->ewgts[0] = (float)-ewgt_sum;
}
/* Increment pointers into edges list. */
cgptr->nedges = nseen;
eptr += nseen;
if (COARSEN_EWGTS)
{
ewptr += nseen;
}
cnedges += nseen - 1;
}
Marshal.FreeHGlobal((IntPtr)seenflag);
/* Form new vertex weights by adding those from contracted edges. */
if (COARSEN_VWGTS)
{
gptr = graph;
for (i = 1; i <= nvtxs; i++)
{
cgraph[v2cv[i]]->vwgt += (*(++gptr))->vwgt;
}
}
/* Reduce arrays to actual sizes */
cnedges /= 2;
size = 2 * cnedges + cnvtxs;
eptr = edges;
edges = (int *)Marshal.ReAllocHGlobal((IntPtr)edges, (IntPtr)(size * sizeof(int)));
if (eptr != edges)
{
/* Need to reset pointers in graph. */
for (i = 1; i <= cnvtxs; i++)
{
cgraph[i]->edges = edges;
edges += cgraph[i]->nedges;
}
}
if (COARSEN_EWGTS)
{
ewptr = eweights;
eweights = (float *)Marshal.ReAllocHGlobal((IntPtr)eweights, (IntPtr)(size * sizeof(float)));
if (ewptr != eweights)
{
/* Need to reset pointers in graph. */
for (i = 1; i <= cnvtxs; i++)
{
cgraph[i]->ewgts = eweights;
eweights += cgraph[i]->nedges;
}
}
}
/* If desired, make new vtx coordinates = center-of-mass of their parents. */
if (coords != null && ccoords != null && igeom > 0)
{
makeccoords(graph, cnvtxs, cv2v_ptrs, cv2v_vals, igeom, coords, ccoords);
}
*pcnedges = cnedges;
Marshal.FreeHGlobal((IntPtr)cv2v_ptrs);
Marshal.FreeHGlobal((IntPtr)cv2v_vals);
if (DEBUG_COARSEN)
{
Trace.WriteLine($" Coarse graph has {cnvtxs:D} vertices and {cnedges:D} edges");
}
make_cgraph_time += seconds() - time;
}