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121 lines
4.7 KiB
121 lines
4.7 KiB
/*
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* Copyright(C) 1999-2020 National Technology & Engineering Solutions
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* of Sandia, LLC (NTESS). Under the terms of Contract DE-NA0003525 with
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* NTESS, the U.S. Government retains certain rights in this software.
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*
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* See packages/seacas/LICENSE for details
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*/
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#include "structs.h" // for vtx_data
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#include <stdio.h> // for NULL
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/* Construct a subgraph of a graph. */
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/* This reuses the graph storage, and can be undone. */
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void make_subgraph(struct vtx_data **graph, /* graph data structure */
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struct vtx_data **subgraph, /* subgraph data structure */
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int subnvtxs, /* number of vtxs in subgraph */
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int * psubnedges, /* ptr to number of edges in subgraph */
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int * assignment, /* values designating subgraph inclusion */
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int set, /* assignment value indicating inclusion */
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int * glob2loc, /* mapping from graph to subgraph numbering */
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int * loc2glob, /* mapping from subgraph to graph numbering */
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int * degree, /* degrees of vertices in graph */
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int using_ewgts /* are edge weights being used? */
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)
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{
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struct vtx_data *subgptr = NULL; /* loops through subgraph */
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float * fptr = NULL; /* loops through edge weights */
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int * iptr = NULL; /* loops through edge list */
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float tempwgt; /* weight of vertex being swapped */
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double ewgtsum; /* sum of weights of subgraph edges */
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int subnedges; /* number of edges in subgraph */
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int neighbor; /* neighbor vertex in graph */
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int newnedges; /* vertex degree in subgraph */
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int tempvtx; /* vertex number being swapped */
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int i, j; /* loop counter */
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subnedges = 0;
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for (i = 1; i <= subnvtxs; i++) {
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/* First get the vertices organized properly. */
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subgptr = subgraph[i] = graph[loc2glob[i]];
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newnedges = degree[i] = subgptr->nedges;
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/* Now work on the edges. */
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subgptr->edges[0] = i;
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ewgtsum = 0;
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/* Move all deactivated edges to the end of the list. */
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iptr = subgptr->edges + 1;
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if (using_ewgts) {
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fptr = subgptr->ewgts + 1;
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}
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for (j = 1; j < newnedges;) {
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neighbor = *iptr;
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if (assignment[neighbor] == set) { /* Keep vertex in edge list. */
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subgptr->edges[j] = glob2loc[neighbor];
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if (using_ewgts) {
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ewgtsum += *fptr++;
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}
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j++;
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iptr++;
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}
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else { /* Move vertex to back of edge list. */
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--newnedges;
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tempvtx = subgptr->edges[newnedges];
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subgptr->edges[newnedges] = neighbor;
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*iptr = tempvtx;
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if (using_ewgts) {
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tempwgt = subgptr->ewgts[newnedges];
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subgptr->ewgts[newnedges] = *fptr;
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*fptr = tempwgt;
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}
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}
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}
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subgptr->nedges = newnedges;
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subnedges += newnedges;
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if (using_ewgts) {
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subgptr->ewgts[0] = -ewgtsum;
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}
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}
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*psubnedges = (subnedges - subnvtxs) / 2;
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}
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/* Undo the construction of the subgraph. */
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void remake_graph(struct vtx_data **subgraph, /* subgraph data structure */
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int subnvtxs, /* number of vtxs in subgraph */
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int * loc2glob, /* mapping from subgraph to graph numbering */
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int * degree, /* degrees of vertices in graph */
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int using_ewgts /* are edge weights being used? */
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)
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{
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struct vtx_data *subgptr; /* loops through subgraph */
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float * fptr; /* loops through edge weights */
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int * iptr; /* loops through adjacency list */
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double ewgtsum; /* sum of weights of subgraph edges */
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int nedges; /* vertex degree in subgraph */
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int i, j; /* loop counter */
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/* For each vertex in subgraph, expand the edge set back out. */
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for (i = 1; i <= subnvtxs; i++) {
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subgptr = subgraph[i];
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subgptr->edges[0] = loc2glob[i];
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nedges = subgptr->nedges;
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/* Change edges back to global numbering system. */
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iptr = subgptr->edges;
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for (j = nedges - 1; j; j--) {
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iptr++;
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*iptr = loc2glob[*iptr];
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}
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subgptr->nedges = degree[i];
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/* Now get the diagonal value right. */
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if (using_ewgts) {
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ewgtsum = 0;
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fptr = subgptr->ewgts;
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for (j = degree[i] - 1; j; j--) {
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ewgtsum += *(++fptr);
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}
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subgptr->ewgts[0] = -ewgtsum;
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}
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}
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}
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