Actual source code: fndsep.c
2: /* fndsep.f -- translated by f2c (version 19931217).
3: */
5: #include <../src/mat/order/order.h>
8: /*****************************************************************/
9: /************* FNDSEP ..... FIND SEPARATOR *************/
10: /*****************************************************************/
11: /* PURPOSE - THIS ROUTINE IS USED TO FIND A SMALL */
12: /* SEPARATOR FOR A CONNECTED COMPONENT SPECIFIED */
13: /* BY MASK IN THE GIVEN GRAPH. */
14: /* */
15: /* INPUT PARAMETERS - */
16: /* ../../.. - IS THE NODE THAT DETERMINES THE MASKED */
17: /* COMPONENT. */
18: /* (XADJ, ADJNCY) - THE ADJACENCY STRUCTURE PAIR. */
19: /* */
20: /* OUTPUT PARAMETERS - */
21: /* NSEP - NUMBER OF VARIABLES IN THE SEPARATOR. */
22: /* SEP - VECTOR CONTAINING THE SEPARATOR NODES. */
23: /* */
24: /* UPDATED PARAMETER - */
25: /* MASK - NODES IN THE SEPARATOR HAVE THEIR MASK */
26: /* VALUES SET TO ZERO. */
27: /* */
28: /* WORKING PARAMETERS - */
29: /* (XLS, LS) - LEVEL STRUCTURE PAIR FOR LEVEL STRUCTURE */
30: /* FOUND BY FN../../... */
31: /* */
32: /* PROGRAM SUBROUTINES - */
33: /* FN../../... */
34: /* */
35: /*****************************************************************/
38: PetscErrorCode SPARSEPACKfndsep(PetscInt *root, PetscInt *xadj, PetscInt *adjncy,
39: PetscInt *mask, PetscInt *nsep, PetscInt *sep, PetscInt *xls, PetscInt *ls)
40: {
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) {
61: goto L200;
62: }
63: *nsep = xls[nlvl + 1] - 1;
64: i__1 = *nsep;
65: for (i = 1; i <= i__1; ++i) {
66: node = ls[i];
67: sep[i] = node;
68: mask[node] = 0;
69: }
70: return(0);
71: /* FIND THE MIDDLE LEVEL OF THE ../../..ED LEVEL STRUCTURE.*/
72: L200:
73: midlvl = (nlvl + 2) / 2;
74: midbeg = xls[midlvl];
75: mp1beg = xls[midlvl + 1];
76: midend = mp1beg - 1;
77: mp1end = xls[midlvl + 2] - 1;
78: /* THE SEPARATOR IS OBTAINED BY INCLUDING ONLY THOSE*/
79: /* MIDDLE-LEVEL NODES WITH NEIGHBORS IN THE MIDDLE+1*/
80: /* LEVEL. XADJ IS USED TEMPORARILY TO MARK THOSE*/
81: /* NODES IN THE MIDDLE+1 LEVEL.*/
82: i__1 = mp1end;
83: for (i = mp1beg; i <= i__1; ++i) {
84: node = ls[i];
85: xadj[node] = -xadj[node];
86: }
87: *nsep = 0;
88: i__1 = midend;
89: for (i = midbeg; i <= i__1; ++i) {
90: node = ls[i];
91: jstrt = xadj[node];
92: jstop = (i__2 = xadj[node + 1], (PetscInt)PetscAbsInt(i__2)) - 1;
93: i__2 = jstop;
94: for (j = jstrt; j <= i__2; ++j) {
95: nbr = adjncy[j];
96: if (xadj[nbr] > 0) {
97: goto L400;
98: }
99: ++(*nsep);
100: sep[*nsep] = node;
101: mask[node] = 0;
102: goto L500;
103: L400:
104: ;
105: }
106: L500:
107: ;
108: }
109: /* RESET XADJ TO ITS CORRECT SIGN.*/
110: i__1 = mp1end;
111: for (i = mp1beg; i <= i__1; ++i) {
112: node = ls[i];
113: xadj[node] = -xadj[node];
114: }
115: return(0);
116: }