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