Actual source code: slo.c

  1: #define PETSCMAT_DLL

  3: /* slo.f -- translated by f2c (version of 25 March 1992  12:58:56).*/

 5:  #include ../src/mat/color/color.h

  9: PetscErrorCode MINPACKslo(PetscInt *n,PetscInt * indrow,PetscInt * jpntr,PetscInt * indcol, PetscInt *ipntr, PetscInt *ndeg,PetscInt * list,
 10:                           PetscInt * maxclq,PetscInt *iwa1,PetscInt * iwa2,PetscInt * iwa3,PetscInt * iwa4)
 11: {
 12:     /* System generated locals */
 13:     PetscInt i__1, i__2, i__3, i__4;

 15:     /* Local variables */
 16:     PetscInt jcol, ic, ip, jp, ir, mindeg, numdeg, numord;

 18: /*     Given the sparsity pattern of an m by n matrix A, this */
 19: /*     subroutine determines the smallest-last ordering of the */
 20: /*     columns of A. */
 21: /*     The smallest-last ordering is defined for the loopless */
 22: /*     graph G with vertices a(j), j = 1,2,...,n where a(j) is the */
 23: /*     j-th column of A and with edge (a(i),a(j)) if and only if */
 24: /*     columns i and j have a non-zero in the same row position. */
 25: /*     The smallest-last ordering is determined recursively by */
 26: /*     letting list(k), k = n,...,1 be a column with least degree */
 27: /*     in the subgraph spanned by the un-ordered columns. */
 28: /*     Note that the value of m is not needed by slo and is */
 29: /*     therefore not present in the subroutine statement. */
 30: /*     The subroutine statement is */
 31: /*       subroutine slo(n,indrow,jpntr,indcol,ipntr,ndeg,list, */
 32: /*                      maxclq,iwa1,iwa2,iwa3,iwa4) */
 33: /*     where */
 34: /*       n is a positive integer input variable set to the number */
 35: /*         of columns of A. */
 36: /*       indrow is an integer input array which contains the row */
 37: /*         indices for the non-zeroes in the matrix A. */
 38: /*       jpntr is an integer input array of length n + 1 which */
 39: /*         specifies the locations of the row indices in indrow. */
 40: /*         The row indices for column j are */
 41: /*               indrow(k), k = jpntr(j),...,jpntr(j+1)-1. */
 42: /*         Note that jpntr(n+1)-1 is then the number of non-zero */
 43: /*         elements of the matrix A. */
 44: /*       indcol is an integer input array which contains the */
 45: /*         column indices for the non-zeroes in the matrix A. */
 46: /*       ipntr is an integer input array of length m + 1 which */
 47: /*         specifies the locations of the column indices in indcol. */
 48: /*         The column indices for row i are */
 49: /*               indcol(k), k = ipntr(i),...,ipntr(i+1)-1. */
 50: /*         Note that ipntr(m+1)-1 is then the number of non-zero */
 51: /*         elements of the matrix A. */
 52: /*       ndeg is an integer input array of length n which specifies */
 53: /*         the degree sequence. The degree of the j-th column */
 54: /*         of A is ndeg(j). */
 55: /*       list is an integer output array of length n which specifies */
 56: /*         the smallest-last ordering of the columns of A. The j-th */
 57: /*         column in this order is list(j). */
 58: /*       maxclq is an integer output variable set to the size */
 59: /*         of the largest clique found during the ordering. */
 60: /*       iwa1,iwa2,iwa3, and iwa4 are integer work arrays of length n. */
 61: /*     Subprograms called */
 62: /*       FORTRAN-supplied ... min */
 63: /*     Argonne National Laboratory. MINPACK Project. August 1984. */
 64: /*     Thomas F. Coleman, Burton S. Garbow, Jorge J. More' */

 67:     /* Parameter adjustments */
 68:     --iwa4;
 69:     --iwa3;
 70:     --iwa2;
 71:     --list;
 72:     --ndeg;
 73:     --ipntr;
 74:     --indcol;
 75:     --jpntr;
 76:     --indrow;

 78:     /* Function Body */
 79:     mindeg = *n;
 80:     i__1 = *n;
 81:     for (jp = 1; jp <= i__1; ++jp) {
 82:         iwa1[jp - 1] = 0;
 83:         iwa4[jp] = *n;
 84:         list[jp] = ndeg[jp];
 85:         /* Computing MIN */
 86:         i__2 = mindeg, i__3 = ndeg[jp];
 87:         mindeg = PetscMin(i__2,i__3);
 88:     }

 90:     /*     Create a doubly-linked list to access the degrees of the */
 91:     /*     columns. The pointers for the linked list are as follows. */

 93:     /*     Each un-ordered column ic is in a list (the degree list) */
 94:     /*     of columns with the same degree. */

 96:     /*     iwa1(numdeg) is the first column in the numdeg list */
 97:     /*     unless iwa1(numdeg) = 0. In this case there are */
 98:     /*     no columns in the numdeg list. */

100:     /*     iwa2(ic) is the column before ic in the degree list */
101:     /*     unless iwa2(ic) = 0. In this case ic is the first */
102:     /*     column in this degree list. */

104:     /*     iwa3(ic) is the column after ic in the degree list */
105:     /*     unless iwa3(ic) = 0. In this case ic is the last */
106:     /*     column in this degree list. */

108:     /*     If ic is an un-ordered column, then list(ic) is the */
109:     /*     degree of ic in the graph induced by the un-ordered */
110:     /*     columns. If jcol is an ordered column, then list(jcol) */
111:     /*     is the smallest-last order of column jcol. */

113:     i__1 = *n;
114:     for (jp = 1; jp <= i__1; ++jp) {
115:         numdeg = ndeg[jp];
116:         iwa2[jp] = 0;
117:         iwa3[jp] = iwa1[numdeg];
118:         if (iwa1[numdeg] > 0) {
119:             iwa2[iwa1[numdeg]] = jp;
120:         }
121:         iwa1[numdeg] = jp;
122:     }
123:     *maxclq = 0;
124:     numord = *n;

126:     /*     Beginning of iteration loop. */

128: L30:

130:     /*        Choose a column jcol of minimal degree mindeg. */

132: L40:
133:     jcol = iwa1[mindeg];
134:     if (jcol > 0) {
135:         goto L50;
136:     }
137:     ++mindeg;
138:     goto L40;
139: L50:
140:     list[jcol] = numord;

142:     /*        Mark the size of the largest clique */
143:     /*        found during the ordering. */

145:     if (mindeg + 1 == numord && !*maxclq) {
146:         *maxclq = numord;
147:     }

149:     /*        Termination test. */

151:     --numord;
152:     if (!numord) {
153:         goto L80;
154:     }

156:     /*        Delete column jcol from the mindeg list. */

158:     iwa1[mindeg] = iwa3[jcol];
159:     if (iwa3[jcol] > 0) {
160:         iwa2[iwa3[jcol]] = 0;
161:     }

163:     /*        Find all columns adjacent to column jcol. */

165:     iwa4[jcol] = 0;

167:     /*        Determine all positions (ir,jcol) which correspond */
168:     /*        to non-zeroes in the matrix. */

170:     i__1 = jpntr[jcol + 1] - 1;
171:     for (jp = jpntr[jcol]; jp <= i__1; ++jp) {
172:         ir = indrow[jp];

174:         /*           For each row ir, determine all positions (ir,ic) */
175:         /*           which correspond to non-zeroes in the matrix. */

177:         i__2 = ipntr[ir + 1] - 1;
178:         for (ip = ipntr[ir]; ip <= i__2; ++ip) {
179:             ic = indcol[ip];

181:             /*              Array iwa4 marks columns which are adjacent to */
182:             /*              column jcol. */

184:             if (iwa4[ic] > numord) {
185:                 iwa4[ic] = numord;

187:                 /*                 Update the pointers to the current degree lists. */

189:                 numdeg = list[ic];
190:                 --list[ic];
191:                 /* Computing MIN */
192:                 i__3 = mindeg, i__4 = list[ic];
193:                 mindeg = PetscMin(i__3,i__4);

195:                 /*                 Delete column ic from the numdeg list. */

197:                 if (!iwa2[ic]) {
198:                     iwa1[numdeg] = iwa3[ic];
199:                 } else {
200:                     iwa3[iwa2[ic]] = iwa3[ic];
201:                 }
202:                 if (iwa3[ic] > 0) {
203:                     iwa2[iwa3[ic]] = iwa2[ic];
204:                 }

206:                 /*                 Add column ic to the numdeg-1 list. */

208:                 iwa2[ic] = 0;
209:                 iwa3[ic] = iwa1[numdeg - 1];
210:                 if (iwa1[numdeg - 1] > 0) {
211:                     iwa2[iwa1[numdeg - 1]] = ic;
212:                 }
213:                 iwa1[numdeg - 1] = ic;
214:             }
215:         }
216:     }

218:     /*        End of iteration loop. */

220:     goto L30;
221: L80:

223:     /*     Invert the array list. */

225:     i__1 = *n;
226:     for (jcol = 1; jcol <= i__1; ++jcol) {
227:         iwa2[list[jcol]] = jcol;
228:     }
229:     i__1 = *n;
230:     for (jp = 1; jp <= i__1; ++jp) {
231:         list[jp] = iwa2[jp];
232:     }
233:     return(0);
234: }