EXODUS/packages/seacas/libraries/chaco/graph/check_graph.c

/*
 * Copyright(C) 1999-2020, 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 "defs.h"
#include "structs.h"
#include <math.h>
#include <stdio.h>

/* Check graph for errors */

int check_graph(struct vtx_data **graph, /* graph data structure */
                int               nvtxs, /* number of vertices */
                int               nedges /* number of edges */
)
{
  extern FILE *Output_File;    /* output file or null */
  float        eweight;        /* edge weight */
  double       wgt_sum = 0.0;  /* sum of edge weights */
  int          flag;           /* flag for error free graph */
  int          no_edge_count;  /* warning flag for isolated vertex */
  int          bad_vwgt_count; /* number of vertices with bad vwgts */
  int          using_ewgts;    /* are edge weights being used? */
  int          narcs;          /* number of neighbors of a vertex */
  int          neighbor;       /* neighbor of a vertex */
  int          i, j;           /* loop counters */

  flag           = FALSE;
  no_edge_count  = 0;
  bad_vwgt_count = 0;
  using_ewgts    = (graph[1]->ewgts != NULL);
  narcs          = 0;
  for (i = 1; i <= nvtxs; i++) {
    narcs += graph[i]->nedges - 1;

    if (graph[i]->edges[0] != i) {
      printf(" Self edge wrong for vtx %d\n", i);
      flag = TRUE;
    }

    if (graph[i]->nedges == 1) {
      if (!no_edge_count) {
        printf("WARNING: Vertex %d has no neighbors\n", i);
        if (Output_File != NULL) {
          fprintf(Output_File, "WARNING: Vertex %d has no neighbors\n", i);
        }
      }
      ++no_edge_count;
    }

    if (graph[i]->vwgt <= 0) {
      if (!bad_vwgt_count) {
        printf("Vertex %d has bad vertex weight %d.\n", i, graph[i]->vwgt);
      }
      ++bad_vwgt_count;
      flag = TRUE;
    }

    if (using_ewgts) {
      wgt_sum = graph[i]->ewgts[0];
    }

    for (j = 1; j < graph[i]->nedges; j++) {
      neighbor = graph[i]->edges[j];
      if (using_ewgts) {
        wgt_sum += graph[i]->ewgts[j];
      }

      /* Move it to the end and delete instead? */
      if (neighbor == i) {
        printf("Self edge (%d,%d) not allowed\n", i, neighbor);
        flag = TRUE;
      }

      if (neighbor < 1 || neighbor > nvtxs) {
        printf("Edge (%d,%d) included, but nvtxs = %d\n", i, neighbor, nvtxs);
        flag = TRUE;
      }

      /* Move it to the end and delete instead? */
      if (using_ewgts && graph[i]->ewgts[j] <= 0) {
        printf("Bad edge weight %g for edge (%d, %d)\n", graph[i]->ewgts[j], i, neighbor);
        flag = TRUE;
      }

      if (!is_an_edge(graph[neighbor], i, &eweight)) {
        printf("Edge (%d,%d) included but not (%d,%d)\n", i, neighbor, neighbor, i);
        flag = TRUE;
      }
      else if (using_ewgts && eweight != graph[i]->ewgts[j]) {
        printf("Weight of (%d,%d)=%g, but weight of (%d,%d)=%g\n", i, neighbor, graph[i]->ewgts[j],
               neighbor, i, eweight);
        flag = TRUE;
      }
    }

    if (using_ewgts && fabs(wgt_sum) > 1.0e-7 * fabs(graph[i]->ewgts[0])) {
      printf("Sum of edge weights for vertex %d = %g\n", i, wgt_sum);
      flag = TRUE;
    }
  }

  if (no_edge_count > 1) {
    printf("WARNING: %d vertices have no neighbors\n", no_edge_count);
    if (Output_File != NULL) {
      fprintf(Output_File, "WARNING: %d vertices have no neighbors\n", no_edge_count);
    }
  }

  if (bad_vwgt_count > 1) {
    printf("%d vertices have bad vertex weights\n", bad_vwgt_count);
  }

  if (narcs != 2 * nedges) {
    printf(" twice nedges = %d, but I count %d\n", 2 * nedges, narcs);
    flag = TRUE;
  }
  return (flag);
}

int is_an_edge(struct 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++) {
    if (vertex->edges[i] == v2) {
      if (vertex->ewgts != NULL) {
        *weight2 = vertex->ewgts[i];
      }
      else {
        *weight2 = 1;
      }
      return (TRUE);
    }
  }

  return (FALSE);
}