matrix2graph.c

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/*****************************************************************************
 * Copyright (c) 2019 FrontISTR Commons
 * This software is released under the MIT License, see LICENSE.txt
 *****************************************************************************/
 
#include "matrix2graph.h"
 
#include <stdio.h>
#include <stdlib.h>
#include "separator.h"
 
void matrix2graph(int num_of_row, int num_of_col, int num_of_nzero, int *irow,
                  int *jcol, graph_type *graph) {
  int i;
  int *count, tmp_nodeid;
 
  graph->xadj = (int *)calloc(num_of_col + 1, sizeof(int));
  if (graph->xadj == NULL) separator_memory_exit("matrix2graph: graph");
  graph->xadj[0] = 0;
  for (i = 0; i < num_of_nzero; i++) {
    if (irow[i] != jcol[i]) {
      graph->xadj[irow[i]]++;
      graph->xadj[jcol[i]]++;
    }
  }
  for (i        = 0; i < num_of_col; i++) graph->xadj[i + 1] += graph->xadj[i];
  graph->adjncy = (int *)calloc(graph->xadj[num_of_col], sizeof(int));
  if (graph->adjncy == NULL) separator_memory_exit("matrix2graph: graph");
  count = (int *)calloc(num_of_row, sizeof(int));
  if (count == NULL) separator_memory_exit("tmp: count");
  for (i = 0; i < num_of_row; i++) count[i] = 0;
  for (i = 0; i < num_of_nzero; i++) {
    if (irow[i] != jcol[i]) {
      tmp_nodeid                                                 = irow[i] - 1;
      graph->adjncy[graph->xadj[tmp_nodeid] + count[tmp_nodeid]] = jcol[i] - 1;
      count[tmp_nodeid]++;
      tmp_nodeid                                                 = jcol[i] - 1;
      graph->adjncy[graph->xadj[tmp_nodeid] + count[tmp_nodeid]] = irow[i] - 1;
      count[tmp_nodeid]++;
    }
  }
  free(count);
  graph->nvtxs  = num_of_col;
  graph->nedges = graph->xadj[num_of_col];
  graph->ncon   = 0;
 
  return;
}