Actual source code: rcm.c
petsc-3.10.5 2019-03-28
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      2: /* rcm.f -- translated by f2c (version 19931217).*/

      4:  #include <petscsys.h>
      5:  #include <petsc/private/matorderimpl.h>

      7: /*****************************************************************/
      8: /*********     RCM ..... REVERSE CUTHILL-MCKEE ORDERING   *******/
      9: /*****************************************************************/
     10: /*    PURPOSE - RCM NUMBERS A CONNECTED COMPONENT SPECIFIED BY    */
     11: /*       MASK AND ../../.., USING THE RCM ALGORITHM.                  */
     12: /*       THE NUMBERING IS TO BE STARTED AT THE NODE ../../...         */
     13: /*                                                               */
     14: /*    INPUT PARAMETERS -                                         */
     15: /*       ../../.. - IS THE NODE THAT DEFINES THE CONNECTED           */
     16: /*              COMPONENT AND IT IS USED AS THE STARTING         */
     17: /*              NODE FOR THE RCM ORDERING.                       */
     18: /*       (XADJ, ADJNCY) - ADJACENCY STRUCTURE PAIR FOR           */
     19: /*              THE GRAPH.                                       */
     20: /*                                                               */
     21: /*    UPDATED PARAMETERS -                                       */
     22: /*       MASK - ONLY THOSE NODES WITH NONZERO INPUT MASK         */
     23: /*              VALUES ARE CONSIDERED BY THE ROUTINE.  THE       */
     24: /*              NODES NUMBERED BY RCM WILL HAVE THEIR            */
     25: /*              MASK VALUES SET TO ZERO.                         */
     26: /*                                                               */
     27: /*    OUTPUT PARAMETERS -                                        */
     28: /*       PERM - WILL CONTAIN THE RCM ORDERING.                   */
     29: /*       CCSIZE - IS THE SIZE OF THE CONNECTED COMPONENT         */
     30: /*              THAT HAS BEEN NUMBERED BY RCM.                  */
     31: /*                                                              */
     32: /*    WORKING PARAMETER -                                       */
     33: /*       DEG - IS A TEMPORARY VECTOR USED TO HOLD THE DEGREE    */
     34: /*              OF THE NODES IN THE SECTION GRAPH SPECIFIED     */
     35: /*              BY MASK AND ../../...                               */
     36: /*                                                              */
     37: /*    PROGRAM SUBROUTINES -                                     */
     38: /*       DEGREE.                                                */
     39: /*                                                              */
     40: /****************************************************************/
     41: PetscErrorCode SPARSEPACKrcm(const PetscInt *root,const PetscInt *xadj,const PetscInt *adjncy,PetscInt *mask, PetscInt *perm, PetscInt *ccsize, PetscInt *deg)
     42: {
     43:   /* System generated locals */
     44:   PetscInt i__1, i__2;

     46:   /* Local variables */
     47:   PetscInt node, fnbr, lnbr, i, j, k, l, lperm, jstop, jstrt;
     48:   PetscInt lbegin, lvlend, nbr;

     50: /*       FIND THE DEGREES OF THE NODES IN THE                  */
     51: /*       COMPONENT SPECIFIED BY MASK AND ../../...                 */
     52: /*       -------------------------------------                 */

     56:   /* Parameter adjustments */
     57:   --deg;
     58:   --perm;
     59:   --mask;
     60:   --adjncy;
     61:   --xadj;

     64:   SPARSEPACKdegree(root, &xadj[1], &adjncy[1], &mask[1], &deg[1], ccsize, &perm[1]);
     65:   mask[*root] = 0;
     66:   if (*ccsize <= 1) return(0);
     67:   lvlend = 0;
     68:   lnbr   = 1;
     69: /*       LBEGIN AND LVLEND POINT TO THE BEGINNING AND */
     70: /*       THE END OF THE CURRENT LEVEL RESPECTIVELY.  */
     71: L100:
     72:   lbegin = lvlend + 1;
     73:   lvlend = lnbr;
     74:   i__1   = lvlend;
     75:   for (i = lbegin; i <= i__1; ++i) {
     76: /*          FOR EACH NODE IN CURRENT LEVEL ...     */
     77:     node  = perm[i];
     78:     jstrt = xadj[node];
     79:     jstop = xadj[node + 1] - 1;

     81: /*          FIND THE UNNUMBERED NEIGHBORS OF NODE.   */
     82: /*          FNBR AND LNBR POINT TO THE FIRST AND LAST  */
     83: /*          UNNUMBERED NEIGHBORS RESPECTIVELY OF THE CURRENT  */
     84: /*          NODE IN PERM. */
     85:     fnbr = lnbr + 1;
     86:     i__2 = jstop;
     87:     for (j = jstrt; j <= i__2; ++j) {
     88:       nbr = adjncy[j];
     89:       if (!mask[nbr]) goto L200;
     90:       ++lnbr;
     91:       mask[nbr]  = 0;
     92:       perm[lnbr] = nbr;
     93: L200:
     94:       ;
     95:     }
     96:     if (fnbr >= lnbr) goto L600;

     98: /*             SORT THE NEIGHBORS OF NODE IN INCREASING    */
     99: /*             ORDER BY DEGREE. LINEAR INSERTION IS USED.*/
    100:     k = fnbr;
    101: L300:
    102:     l = k;
    103:     ++k;
    104:     nbr = perm[k];
    105: L400:
    106:     if (l < fnbr) goto L500;
    107:     lperm = perm[l];
    108:     if (deg[lperm] <= deg[nbr]) goto L500;
    109:     perm[l + 1] = lperm;
    110:     --l;
    111:     goto L400;
    112: L500:
    113:     perm[l + 1] = nbr;
    114:     if (k < lnbr) goto L300;
    115: L600:
    116:     ;
    117:   }
    118:   if (lnbr > lvlend) goto L100;

    120: /*       WE NOW HAVE THE CUTHILL MCKEE ORDERING.*/
    121: /*       REVERSE IT BELOW ...*/
    122:   k    = *ccsize / 2;
    123:   l    = *ccsize;
    124:   i__1 = k;
    125:   for (i = 1; i <= i__1; ++i) {
    126:     lperm   = perm[l];
    127:     perm[l] = perm[i];
    128:     perm[i] = lperm;
    129:     --l;
    130:   }
    131:   return(0);
    132: }