Date: 2026-06-01T23:13:30+00:00

Actual source code: fndsep.c

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

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

      6: /*****************************************************************/
      7: /*************     FNDSEP ..... FIND SEPARATOR       *************/
      8: /*****************************************************************/
      9: /*    PURPOSE - THIS ROUTINE IS USED TO FIND A SMALL             */
     10: /*              SEPARATOR FOR A CONNECTED COMPONENT SPECIFIED    */
     11: /*              BY MASK IN THE GIVEN GRAPH.                      */
     12: /*                                                               */
     13: /*    INPUT PARAMETERS -                                         */
     14: /*       ROOT - IS THE NODE THAT DETERMINES THE MASKED           */
     15: /*              COMPONENT.                                       */
     16: /*       (XADJ, ADJNCY) - THE ADJACENCY STRUCTURE PAIR.          */
     17: /*                                                               */
     18: /*    OUTPUT PARAMETERS -                                        */
     19: /*       NSEP - NUMBER OF VARIABLES IN THE SEPARATOR.            */
     20: /*       SEP - VECTOR CONTAINING THE SEPARATOR NODES.            */
     21: /*                                                               */
     22: /*    UPDATED PARAMETER -                                        */
     23: /*       MASK - NODES IN THE SEPARATOR HAVE THEIR MASK           */
     24: /*              VALUES SET TO ZERO.                              */
     25: /*                                                               */
     26: /*    WORKING PARAMETERS -                                       */
     27: /*       (XLS, LS) - LEVEL STRUCTURE PAIR FOR LEVEL STRUCTURE    */
     28: /*              FOUND BY FNROOT.                                 */
     29: /*                                                               */
     30: /*    PROGRAM SUBROUTINES -                                      */
     31: /*       FNROOT.                                                 */
     32: /*                                                               */
     33: /*****************************************************************/
     34: PetscErrorCode SPARSEPACKfndsep(PetscInt *root, const PetscInt *inxadj, const PetscInt *adjncy, PetscInt *mask, PetscInt *nsep, PetscInt *sep, PetscInt *xls, PetscInt *ls)
     35: {
     36:   PetscInt *xadj = (PetscInt *)inxadj; /* Used as temporary and reset within this function */

     38:   /* System generated locals */
     39:   PetscInt i__1, i__2;

     41:   /* Local variables */
     42:   PetscInt node, nlvl, i, j, jstop, jstrt, mp1beg, mp1end, midbeg, midend, midlvl;
     43:   PetscInt nbr;

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

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