1: /* rcm.f -- translated by f2c (version 19931217).*/

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

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

 42:   /* Local variables */
 43:   PetscInt node, fnbr, lnbr, i, j, k, l, lperm, jstop, jstrt;
 44:   PetscInt lbegin, lvlend, nbr;

 46:   /*       FIND THE DEGREES OF THE NODES IN THE                  */
 47:   /*       COMPONENT SPECIFIED BY MASK AND ROOT.                 */

 49:   PetscFunctionBegin;
 50:   /* Parameter adjustments */
 51:   --deg;
 52:   --perm;
 53:   --mask;
 54:   --adjncy;
 55:   --xadj;

 57:   PetscCall(SPARSEPACKdegree(root, &xadj[1], &adjncy[1], &mask[1], &deg[1], ccsize, &perm[1]));
 58:   mask[*root] = 0;
 59:   if (*ccsize <= 1) PetscFunctionReturn(PETSC_SUCCESS);
 60:   lvlend = 0;
 61:   lnbr   = 1;
 62: /*       LBEGIN AND LVLEND POINT TO THE BEGINNING AND */
 63: /*       THE END OF THE CURRENT LEVEL RESPECTIVELY.  */
 64: L100:
 65:   lbegin = lvlend + 1;
 66:   lvlend = lnbr;
 67:   i__1   = lvlend;
 68:   for (i = lbegin; i <= i__1; ++i) {
 69:     /*          FOR EACH NODE IN CURRENT LEVEL ...     */
 70:     node  = perm[i];
 71:     jstrt = xadj[node];
 72:     jstop = xadj[node + 1] - 1;

 74:     /*          FIND THE UNNUMBERED NEIGHBORS OF NODE.   */
 75:     /*          FNBR AND LNBR POINT TO THE FIRST AND LAST  */
 76:     /*          UNNUMBERED NEIGHBORS RESPECTIVELY OF THE CURRENT  */
 77:     /*          NODE IN PERM. */
 78:     fnbr = lnbr + 1;
 79:     i__2 = jstop;
 80:     for (j = jstrt; j <= i__2; ++j) {
 81:       nbr = adjncy[j];
 82:       if (!mask[nbr]) goto L200;
 83:       ++lnbr;
 84:       mask[nbr]  = 0;
 85:       perm[lnbr] = nbr;
 86:     L200:;
 87:     }
 88:     if (fnbr >= lnbr) goto L600;

 90:     /*             SORT THE NEIGHBORS OF NODE IN INCREASING    */
 91:     /*             ORDER BY DEGREE. LINEAR INSERTION IS USED.*/
 92:     k = fnbr;
 93:   L300:
 94:     l = k;
 95:     ++k;
 96:     nbr = perm[k];
 97:   L400:
 98:     if (l < fnbr) goto L500;
 99:     lperm = perm[l];
100:     if (deg[lperm] <= deg[nbr]) goto L500;
101:     perm[l + 1] = lperm;
102:     --l;
103:     goto L400;
104:   L500:
105:     perm[l + 1] = nbr;
106:     if (k < lnbr) goto L300;
107:   L600:;
108:   }
109:   if (lnbr > lvlend) goto L100;

111:   /*       WE NOW HAVE THE CUTHILL MCKEE ORDERING.*/
112:   /*       REVERSE IT BELOW ...*/
113:   k    = *ccsize / 2;
114:   l    = *ccsize;
115:   i__1 = k;
116:   for (i = 1; i <= i__1; ++i) {
117:     lperm   = perm[l];
118:     perm[l] = perm[i];
119:     perm[i] = lperm;
120:     --l;
121:   }
122:   PetscFunctionReturn(PETSC_SUCCESS);
123: }