Actual source code: fnroot.c

  2: /* fnroot.f -- translated by f2c (version 19931217).*/

  4: #include <petscsys.h>


  8: /*****************************************************************/
  9: /********     FN../../.. ..... FIND PSEUDO-PERIPHERAL NODE    ********/
 10: /*****************************************************************/
 11: /*   PURPOSE - FN../../.. IMPLEMENTS A MODIFIED VERSION OF THE       */
 12: /*      SCHEME BY GIBBS, POOLE, AND STOCKMEYER TO FIND PSEUDO-   */
 13: /*      PERIPHERAL NODES.  IT DETERMINES SUCH A NODE FOR THE     */
 14: /*      SECTION SUBGRAPH SPECIFIED BY MASK AND ../../...             */
 15: /*   INPUT PARAMETERS -                                          */
 16: /*      (XADJ, ADJNCY) - ADJACENCY STRUCTURE PAIR FOR THE GRAPH. */
 17: /*      MASK - SPECIFIES A SECTION SUBGRAPH. NODES FOR WHICH     */
 18: /*             MASK IS ZERO ARE IGNORED BY FN../../...              */
 19: /*   UPDATED PARAMETER -                                        */
 20: /*      ../../.. - ON INPUT, IT (ALONG WITH MASK) DEFINES THE       */
 21: /*             COMPONENT FOR WHICH A PSEUDO-PERIPHERAL NODE IS  */
 22: /*             TO BE FOUND. ON OUTPUT, IT IS THE NODE OBTAINED. */
 23: /*                                                              */
 24: /*   OUTPUT PARAMETERS -                                        */
 25: /*      NLVL - IS THE NUMBER OF LEVELS IN THE LEVEL STRUCTURE   */
 26: /*             ../../..ED AT THE NODE ../../...                         */
 27: /*      (XLS,LS) - THE LEVEL STRUCTURE ARRAY PAIR CONTAINING    */
 28: /*                 THE LEVEL STRUCTURE FOUND.                   */
 29: /*                                                              */
 30: /*   PROGRAM SUBROUTINES -                                      */
 31: /*      ../../..LS.                                                 */
 32: /*                                                              */
 33: /****************************************************************/
 36: PetscErrorCode SPARSEPACKfnroot(PetscInt *root, PetscInt *xadj, PetscInt *adjncy,  
 37:                                 PetscInt *mask, PetscInt *nlvl, PetscInt *xls, PetscInt *ls)
 38: {
 39:     /* System generated locals */
 40:     PetscInt i__1, i__2;

 42:     /* Local variables */
 43:     PetscInt ndeg, node, j, k, nabor, kstop, jstrt, kstrt, mindeg, ccsize, nunlvl;
 44: /*       DETERMINE THE LEVEL STRUCTURE ../../..ED AT ../../... */

 47:     /* Parameter adjustments */
 48:     --ls;
 49:     --xls;
 50:     --mask;
 51:     --adjncy;
 52:     --xadj;

 54:     SPARSEPACKrootls(root, &xadj[1], &adjncy[1], &mask[1], nlvl, &xls[1], &ls[1]);
 55:     ccsize = xls[*nlvl + 1] - 1;
 56:     if (*nlvl == 1 || *nlvl == ccsize) {
 57:         return(0);
 58:     }
 59: /*       PICK A NODE WITH MINIMUM DEGREE FROM THE LAST LEVEL.*/
 60: L100:
 61:     jstrt = xls[*nlvl];
 62:     mindeg = ccsize;
 63:     *root = ls[jstrt];
 64:     if (ccsize == jstrt) {
 65:         goto L400;
 66:     }
 67:     i__1 = ccsize;
 68:     for (j = jstrt; j <= i__1; ++j) {
 69:         node = ls[j];
 70:         ndeg = 0;
 71:         kstrt = xadj[node];
 72:         kstop = xadj[node + 1] - 1;
 73:         i__2 = kstop;
 74:         for (k = kstrt; k <= i__2; ++k) {
 75:             nabor = adjncy[k];
 76:             if (mask[nabor] > 0) {
 77:                 ++ndeg;
 78:             }
 79:         }
 80:         if (ndeg >= mindeg) {
 81:             goto L300;
 82:         }
 83:         *root = node;
 84:         mindeg = ndeg;
 85: L300:
 86:         ;
 87:     }
 88: /*       AND GENERATE ITS ../../..ED LEVEL STRUCTURE.*/
 89: L400:
 90:     SPARSEPACKrootls(root, &xadj[1], &adjncy[1], &mask[1], &nunlvl, &xls[1], &ls[1]);
 91:     if (nunlvl <= *nlvl) {
 92:         return(0);
 93:     }
 94:     *nlvl = nunlvl;
 95:     if (*nlvl < ccsize) {
 96:         goto L100;
 97:     }
 98:     return(0);
 99: }