Actual source code: fndsep.c
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: /*****************************************************************/
35: PetscErrorCode SPARSEPACKfndsep(PetscInt *root, const PetscInt *inxadj, const PetscInt *adjncy, PetscInt *mask, PetscInt *nsep, PetscInt *sep, PetscInt *xls, PetscInt *ls)
36: {
37: PetscInt *xadj = (PetscInt *)inxadj; /* Used as temporary and reset within this function */
39: /* System generated locals */
40: PetscInt i__1, i__2;
42: /* Local variables */
43: PetscInt node, nlvl, i, j, jstop, jstrt, mp1beg, mp1end, midbeg, midend, midlvl;
44: PetscInt nbr;
46: /* Parameter adjustments */
47: --ls;
48: --xls;
49: --sep;
50: --mask;
51: --adjncy;
52: --xadj;
54: 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: return 0;
66: /* FIND THE MIDDLE LEVEL OF THE ../../..ED 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 = (PetscInt)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: return 0;
108: }