code: public int[] getIR()
      {
          int[] ir = new int[nzmax];
          int i = 0;
          for ( IndexMN index : indexSet )
          {
              ir[i++] = index.m;
          }
          return ir;
      }
docs: Gets row indices
  
  <tt>ir</tt> points to an integer array of length nzmax containing the row indices of
  the corresponding elements in <tt>pr</tt> and <tt>pi</tt>.