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

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

      7: /*****************************************************************/
      8: /********     FN../../.. ..... FIND PSEUDO-PERIPHERAL NODE    ********/
      9: /*****************************************************************/
     10: /*   PURPOSE - FN../../.. IMPLEMENTS A MODIFIED VERSION OF THE       */
     11: /*      SCHEME BY GIBBS, POOLE, AND STOCKMEYER TO FIND PSEUDO-   */
     12: /*      PERIPHERAL NODES.  IT DETERMINES SUCH A NODE FOR THE     */
     13: /*      SECTION SUBGRAPH SPECIFIED BY MASK AND ../../...             */
     14: /*   INPUT PARAMETERS -                                          */
     15: /*      (XADJ, ADJNCY) - ADJACENCY STRUCTURE PAIR FOR THE GRAPH. */
     16: /*      MASK - SPECIFIES A SECTION SUBGRAPH. NODES FOR WHICH     */
     17: /*             MASK IS ZERO ARE IGNORED BY FN../../...              */
     18: /*   UPDATED PARAMETER -                                        */
     19: /*      ../../.. - ON INPUT, IT (ALONG WITH MASK) DEFINES THE       */
     20: /*             COMPONENT FOR WHICH A PSEUDO-PERIPHERAL NODE IS  */
     21: /*             TO BE FOUND. ON OUTPUT, IT IS THE NODE OBTAINED. */
     22: /*                                                              */
     23: /*   OUTPUT PARAMETERS -                                        */
     24: /*      NLVL - IS THE NUMBER OF LEVELS IN THE LEVEL STRUCTURE   */
     25: /*             ../../..ED AT THE NODE ../../...                         */
     26: /*      (XLS,LS) - THE LEVEL STRUCTURE ARRAY PAIR CONTAINING    */
     27: /*                 THE LEVEL STRUCTURE FOUND.                   */
     28: /*                                                              */
     29: /*   PROGRAM SUBROUTINES -                                      */
     30: /*      ../../..LS.                                                 */
     31: /*                                                              */
     32: /****************************************************************/
     33: PetscErrorCode SPARSEPACKfnroot(PetscInt *root,const PetscInt *xadj,const PetscInt *adjncy,PetscInt *mask, PetscInt *nlvl, PetscInt *xls, PetscInt *ls)
     34: {
     35:   /* System generated locals */
     36:   PetscInt i__1, i__2;

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

     43:   /* Parameter adjustments */
     44:   --ls;
     45:   --xls;
     46:   --mask;
     47:   --adjncy;
     48:   --xadj;

     50:   SPARSEPACKrootls(root, &xadj[1], &adjncy[1], &mask[1], nlvl, &xls[1], &ls[1]);
     51:   ccsize = xls[*nlvl + 1] - 1;
     52:   if (*nlvl == 1 || *nlvl == ccsize) return(0);

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