2: /* fndsep.f -- translated by f2c (version 19931217).
  3: */

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

  7: /*****************************************************************/
  8: /*************     FNDSEP ..... FIND SEPARATOR       *************/
  9: /*****************************************************************/
 10: /*    PURPOSE - THIS ROUTINE IS USED TO FIND A SMALL             */
 11: /*              SEPARATOR FOR A CONNECTED COMPONENT SPECIFIED    */
 12: /*              BY MASK IN THE GIVEN GRAPH.                      */
 13: /*                                                               */
 14: /*    INPUT PARAMETERS -                                         */
 15: /*       ../../.. - IS THE NODE THAT DETERMINES THE MASKED           */
 16: /*              COMPONENT.                                       */
 17: /*       (XADJ, ADJNCY) - THE ADJACENCY STRUCTURE PAIR.          */
 18: /*                                                               */
 19: /*    OUTPUT PARAMETERS -                                        */
 20: /*       NSEP - NUMBER OF VARIABLES IN THE SEPARATOR.            */
 21: /*       SEP - VECTOR CONTAINING THE SEPARATOR NODES.            */
 22: /*                                                               */
 23: /*    UPDATED PARAMETER -                                        */
 24: /*       MASK - NODES IN THE SEPARATOR HAVE THEIR MASK           */
 25: /*              VALUES SET TO ZERO.                              */
 26: /*                                                               */
 27: /*    WORKING PARAMETERS -                                       */
 28: /*       (XLS, LS) - LEVEL STRUCTURE PAIR FOR LEVEL STRUCTURE    */
 29: /*              FOUND BY FN../../...                                 */
 30: /*                                                               */
 31: /*    PROGRAM SUBROUTINES -                                      */
 32: /*       FN../../...                                                 */
 33: /*                                                               */
 34: /*****************************************************************/
 37: PetscErrorCode SPARSEPACKfndsep(PetscInt *root,const PetscInt *inxadj,const PetscInt *adjncy,PetscInt *mask, PetscInt *nsep, PetscInt *sep, PetscInt *xls, PetscInt *ls)
 38: {
 39:   PetscInt *xadj = (PetscInt*)inxadj; /* Used as temporary and reset within this function */

 41:   /* System generated locals */
 42:   PetscInt i__1, i__2;

 44:   /* Local variables */
 45:   PetscInt node, nlvl, i, j, jstop, jstrt, mp1beg, mp1end, midbeg, midend, midlvl;
 46:   PetscInt nbr;

 49:   /* Parameter adjustments */
 50:   --ls;
 51:   --xls;
 52:   --sep;
 53:   --mask;
 54:   --adjncy;
 55:   --xadj;

 57:   SPARSEPACKfnroot(root, &xadj[1], &adjncy[1], &mask[1], &nlvl, &xls[1], &ls[1]);
 58: /*       IF THE NUMBER OF LEVELS IS LESS THAN 3, RETURN */
 59: /*       THE WHOLE COMPONENT AS THE SEPARATOR.*/
 60:   if (nlvl >= 3) goto L200;
 61:   *nsep = xls[nlvl + 1] - 1;
 62:   i__1  = *nsep;
 63:   for (i = 1; i <= i__1; ++i) {
 64:     node       = ls[i];
 65:     sep[i]     = node;
 66:     mask[node] = 0;
 67:   }
 68:   return(0);
 69: /*       FIND THE MIDDLE LEVEL OF THE ../../..ED LEVEL STRUCTURE.*/
 70: L200:
 71:   midlvl = (nlvl + 2) / 2;
 72:   midbeg = xls[midlvl];
 73:   mp1beg = xls[midlvl + 1];
 74:   midend = mp1beg - 1;
 75:   mp1end = xls[midlvl + 2] - 1;
 76: /*       THE SEPARATOR IS OBTAINED BY INCLUDING ONLY THOSE*/
 77: /*       MIDDLE-LEVEL NODES WITH NEIGHBORS IN THE MIDDLE+1*/
 78: /*       LEVEL. XADJ IS USED TEMPORARILY TO MARK THOSE*/
 79: /*       NODES IN THE MIDDLE+1 LEVEL.*/
 80:   i__1 = mp1end;
 81:   for (i = mp1beg; i <= i__1; ++i) {
 82:     node       = ls[i];
 83:     xadj[node] = -xadj[node];
 84:   }
 85:   *nsep = 0;
 86:   i__1  = midend;
 87:   for (i = midbeg; i <= i__1; ++i) {
 88:     node  = ls[i];
 89:     jstrt = xadj[node];
 90:     jstop = (i__2 = xadj[node + 1], (PetscInt)PetscAbsInt(i__2)) - 1;
 91:     i__2  = jstop;
 92:     for (j = jstrt; j <= i__2; ++j) {
 93:       nbr = adjncy[j];
 94:       if (xadj[nbr] > 0) goto L400;
 95:       ++(*nsep);
 96:       sep[*nsep] = node;
 97:       mask[node] = 0;
 98:       goto L500;
 99: L400:
100:       ;
101:     }
102: L500:
103:     ;
104:   }
105: /*       RESET XADJ TO ITS CORRECT SIGN.*/
106:   i__1 = mp1end;
107:   for (i = mp1beg; i <= i__1; ++i) {
108:     node       = ls[i];
109:     xadj[node] = -xadj[node];
110:   }
111:   return(0);
112: }