/*
* Copyright(C) 1999-2020, 2022, 2023 National Technology & Engineering Solutions
* of Sandia, LLC (NTESS). Under the terms of Contract DE-NA0003525 with
* NTESS, the U.S. Government retains certain rights in this software.
*
* See packages/seacas/LICENSE for details
*/
#include "smalloc.h" // for smalloc, sfree, srealloc
#include "structs.h" // for vtx_data
#include <stdio.h> // for NULL, printf
static void makecv2v(int nvtxs, /* number of vertices in graph */
int cnvtxs, /* number of vtxs in coarsened graph */
int *v2cv, /* mapping from vtxs to coarsened vtxs */
int *cv2v_vals, /* vtxs corresponding to each cvtx */
int *cv2v_ptrs /* indices into cv2c_vals */
);
void makefgraph(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 cnvtxs, /* number of vtxs in coarsened graph */
int *pcnedges, /* number of edges in coarsened graph */
int *v2cv, /* mapping from vtxs to coarsened vtxs */
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 */
)
{
extern double make_cgraph_time;
extern int DEBUG_COARSEN; /* debug flag for coarsening output */
extern int COARSEN_VWGTS; /* turn off vertex weights in coarse graph? */
extern int COARSEN_EWGTS; /* turn off edge weights in coarse graph? */
struct vtx_data **cgraph = NULL; /* coarsened version of graph */
struct vtx_data *links = NULL; /* space for all the vertex data */
struct vtx_data **gptr = NULL; /* loops through cgraph */
struct 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 = smalloc(nvtxs * sizeof(int));
cv2v_ptrs = smalloc((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 = smalloc((cnvtxs + 1) * sizeof(struct vtx_data *));
links = smalloc(cnvtxs * sizeof(struct vtx_data));
size = 2 * cnedges + cnvtxs;
edges = smalloc(size * sizeof(int));
if (COARSEN_EWGTS) {
ewptr = eweights = smalloc(size * sizeof(float));
}
/* Zero all the seen flags. */
seenflag = smalloc((cnvtxs + 1) * sizeof(int));
sptr = seenflag;
for (i = cnvtxs; i; 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; i--) {
vtx = *sptr++;
iptr = graph[vtx]->edges;
if (using_ewgts) {
fptr = graph[vtx]->ewgts;
}
for (j = graph[vtx]->nedges - 1; j; j--) {
neighbor = *(++iptr);
cneighbor = v2cv[neighbor];
if (cneighbor != cvtx) {
if (using_ewgts) {
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 (using_ewgts) {
++fptr;
}
}
}
/* Now clear the seenflag values. */
iptr = cgptr->edges;
for (j = nseen - 1; j; j--) {
seenflag[*(++iptr)] = 0;
}
if (COARSEN_EWGTS) {
cgptr->ewgts[0] = -ewgt_sum;
}
/* Increment pointers into edges list. */
cgptr->nedges = nseen;
eptr += nseen;
if (COARSEN_EWGTS) {
ewptr += nseen;
}
cnedges += nseen - 1;
}
sfree(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 = srealloc(edges, 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 = srealloc(eweights, 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;
sfree(cv2v_ptrs);
sfree(cv2v_vals);
if (DEBUG_COARSEN > 0) {
printf(" Coarse graph has %d vertices and %d edges\n", cnvtxs, cnedges);
}
make_cgraph_time += seconds() - time;
}
static void makecv2v(int nvtxs, /* number of vertices in graph */
int cnvtxs, /* number of vtxs in coarsened graph */
int *v2cv, /* mapping from vtxs to coarsened vtxs */
int *cv2v_vals, /* vtxs corresponding to each cvtx */
int *cv2v_ptrs /* indices into cv2c_vals */
)
{
int sum; /* cumulative offsets into vals array */
int i; /* loop counter */
/* First find number of vtxs associated with each coarse graph vtx. */
for (i = 1; i <= cnvtxs + 1; i++) {
cv2v_ptrs[i] = 0;
}
for (i = 1; i <= nvtxs; i++) {
++cv2v_ptrs[v2cv[i] + 1]; /* +1 offsets and simplifies next loop. */
}
cv2v_ptrs[1] = 0;
/* Now make this a cumulative total to index into cv2v_vals. */
sum = 0;
for (i = 2; i <= cnvtxs + 1; i++) {
cv2v_ptrs[i] += sum;
sum = cv2v_ptrs[i];
}
/* Now go ahead and set the cv2v_vals. */
for (i = 1; i <= nvtxs; i++) {
cv2v_vals[cv2v_ptrs[v2cv[i]]] = i;
++cv2v_ptrs[v2cv[i]];
}
/* Finally, reset the cv2v_ptrs values. */
for (i = cnvtxs; i; i--) {
cv2v_ptrs[i] = cv2v_ptrs[i - 1];
}
cv2v_ptrs[1] = 0;
}