Actual source code: ido.c

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

  3: #include <../src/mat/color/impls/minpack/color.h>

  5: static PetscInt c_n1 = -1;

  7: PetscErrorCode MINPACKido(PetscInt *m, PetscInt *n, const PetscInt *indrow, const PetscInt *jpntr, const PetscInt *indcol, const PetscInt *ipntr, PetscInt *ndeg, PetscInt *list, PetscInt *maxclq, PetscInt *iwa1, PetscInt *iwa2, PetscInt *iwa3, PetscInt *iwa4)
  8: {
  9:   /* System generated locals */
 10:   PetscInt i__1, i__2, i__3, i__4;

 12:   /* Local variables */
 13:   PetscInt jcol = 0, ncomp = 0, ic, ip, jp, ir, maxinc, numinc, numord, maxlst, numwgt, numlst;

 15:   /*     Given the sparsity pattern of an m by n matrix A, this */
 16:   /*     subroutine determines an incidence-degree ordering of the */
 17:   /*     columns of A. */
 18:   /*     The incidence-degree ordering is defined for the loopless */
 19:   /*     graph G with vertices a(j), j = 1,2,...,n where a(j) is the */
 20:   /*     j-th column of A and with edge (a(i),a(j)) if and only if */
 21:   /*     columns i and j have a non-zero in the same row position. */
 22:   /*     The incidence-degree ordering is determined recursively by */
 23:   /*     letting list(k), k = 1,...,n be a column with maximal */
 24:   /*     incidence to the subgraph spanned by the ordered columns. */
 25:   /*     Among all the columns of maximal incidence, ido chooses a */
 26:   /*     column of maximal degree. */
 27:   /*     The subroutine statement is */
 28:   /*       subroutine ido(m,n,indrow,jpntr,indcol,ipntr,ndeg,list, */
 29:   /*                      maxclq,iwa1,iwa2,iwa3,iwa4) */
 30:   /*     where */
 31:   /*       m is a positive integer input variable set to the number */
 32:   /*         of rows of A. */
 33:   /*       n is a positive integer input variable set to the number */
 34:   /*         of columns of A. */
 35:   /*       indrow is an integer input array which contains the row */
 36:   /*         indices for the non-zeroes in the matrix A. */
 37:   /*       jpntr is an integer input array of length n + 1 which */
 38:   /*         specifies the locations of the row indices in indrow. */
 39:   /*         The row indices for column j are */
 40:   /*               indrow(k), k = jpntr(j),...,jpntr(j+1)-1. */
 41:   /*         Note that jpntr(n+1)-1 is then the number of non-zero */
 42:   /*         elements of the matrix A. */
 43:   /*       indcol is an integer input array which contains the */
 44:   /*         column indices for the non-zeroes in the matrix A. */
 45:   /*       ipntr is an integer input array of length m + 1 which */
 46:   /*         specifies the locations of the column indices in indcol. */
 47:   /*         The column indices for row i are */
 48:   /*               indcol(k), k = ipntr(i),...,ipntr(i+1)-1. */
 49:   /*         Note that ipntr(m+1)-1 is then the number of non-zero */
 50:   /*         elements of the matrix A. */
 51:   /*       ndeg is an integer input array of length n which specifies */
 52:   /*         the degree sequence. The degree of the j-th column */
 53:   /*         of A is ndeg(j). */
 54:   /*       list is an integer output array of length n which specifies */
 55:   /*         the incidence-degree ordering of the columns of A. The j-th */
 56:   /*         column in this order is list(j). */
 57:   /*       maxclq is an integer output variable set to the size */
 58:   /*         of the largest clique found during the ordering. */
 59:   /*       iwa1,iwa2,iwa3, and iwa4 are integer work arrays of length n. */
 60:   /*     Subprograms called */
 61:   /*       MINPACK-supplied ... numsrt */
 62:   /*       FORTRAN-supplied ... max */
 63:   /*     Argonne National Laboratory. MINPACK Project. August 1984. */
 64:   /*     Thomas F. Coleman, Burton S. Garbow, Jorge J. More' */

 66:   /*     Sort the degree sequence. */

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

 80:   /* Function Body */
 81:   i__1 = *n - 1;
 82:   PetscCall(MINPACKnumsrt(n, &i__1, &ndeg[1], &c_n1, &iwa4[1], &iwa2[1], &iwa3[1]));

 84:   /*     Initialization block. */
 85:   /*     Create a doubly-linked list to access the incidences of the */
 86:   /*     columns. The pointers for the linked list are as follows. */
 87:   /*     Each un-ordered column ic is in a list (the incidence list) */
 88:   /*     of columns with the same incidence. */
 89:   /*     iwa1(numinc) is the first column in the numinc list */
 90:   /*     unless iwa1(numinc) = 0. In this case there are */
 91:   /*     no columns in the numinc list. */
 92:   /*     iwa2(ic) is the column before ic in the incidence list */
 93:   /*     unless iwa2(ic) = 0. In this case ic is the first */
 94:   /*     column in this incidence list. */
 95:   /*     iwa3(ic) is the column after ic in the incidence list */
 96:   /*     unless iwa3(ic) = 0. In this case ic is the last */
 97:   /*     column in this incidence list. */
 98:   /*     If ic is an un-ordered column, then list(ic) is the */
 99:   /*     incidence of ic to the graph induced by the ordered */
100:   /*     columns. If jcol is an ordered column, then list(jcol) */
101:   /*     is the incidence-degree order of column jcol. */

103:   maxinc = 0;
104:   for (jp = *n; jp >= 1; --jp) {
105:     ic            = iwa4[jp];
106:     iwa1[*n - jp] = 0;
107:     iwa2[ic]      = 0;
108:     iwa3[ic]      = iwa1[0];
109:     if (iwa1[0] > 0) iwa2[iwa1[0]] = ic;
110:     iwa1[0]  = ic;
111:     iwa4[jp] = 0;
112:     list[jp] = 0;
113:   }

115:   /*     Determine the maximal search length for the list */
116:   /*     of columns of maximal incidence. */

118:   maxlst = 0;
119:   i__1   = *m;
120:   for (ir = 1; ir <= i__1; ++ir) {
121:     /* Computing 2nd power */
122:     i__2 = ipntr[ir + 1] - ipntr[ir];
123:     maxlst += i__2 * i__2;
124:   }
125:   maxlst /= *n;
126:   *maxclq = 0;
127:   numord  = 1;

129:   /*     Beginning of iteration loop. */

131: L30:

133:   /*        Choose a column jcol of maximal degree among the */
134:   /*        columns of maximal incidence maxinc. */

136: L40:
137:   jp = iwa1[maxinc];
138:   if (jp > 0) goto L50;
139:   --maxinc;
140:   goto L40;
141: L50:
142:   numwgt = -1;
143:   i__1   = maxlst;
144:   for (numlst = 1; numlst <= i__1; ++numlst) {
145:     if (ndeg[jp] > numwgt) {
146:       numwgt = ndeg[jp];
147:       jcol   = jp;
148:     }
149:     jp = iwa3[jp];
150:     if (jp <= 0) goto L70;
151:   }
152: L70:
153:   list[jcol] = numord;

155:   /*        Update the size of the largest clique */
156:   /*        found during the ordering. */

158:   if (!maxinc) ncomp = 0;
159:   ++ncomp;
160:   if (maxinc + 1 == ncomp) *maxclq = PetscMax(*maxclq, ncomp);

162:   /*        Termination test. */

164:   ++numord;
165:   if (numord > *n) goto L100;

167:   /*        Delete column jcol from the maxinc list. */

169:   if (!iwa2[jcol]) iwa1[maxinc] = iwa3[jcol];
170:   else iwa3[iwa2[jcol]] = iwa3[jcol];

172:   if (iwa3[jcol] > 0) iwa2[iwa3[jcol]] = iwa2[jcol];

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

176:   iwa4[jcol] = *n;

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

181:   i__1 = jpntr[jcol + 1] - 1;
182:   for (jp = jpntr[jcol]; jp <= i__1; ++jp) {
183:     ir = indrow[jp];

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

188:     i__2 = ipntr[ir + 1] - 1;
189:     for (ip = ipntr[ir]; ip <= i__2; ++ip) {
190:       ic = indcol[ip];

192:       /*              Array iwa4 marks columns which are adjacent to */
193:       /*              column jcol. */

195:       if (iwa4[ic] < numord) {
196:         iwa4[ic] = numord;

198:         /*                 Update the pointers to the current incidence lists. */

200:         numinc = list[ic];
201:         ++list[ic];
202:         /* Computing MAX */
203:         i__3   = maxinc;
204:         i__4   = list[ic];
205:         maxinc = PetscMax(i__3, i__4);

207:         /*                 Delete column ic from the numinc list. */

209:         if (!iwa2[ic]) iwa1[numinc] = iwa3[ic];
210:         else iwa3[iwa2[ic]] = iwa3[ic];

212:         if (iwa3[ic] > 0) iwa2[iwa3[ic]] = iwa2[ic];

214:         /*                 Add column ic to the numinc+1 list. */

216:         iwa2[ic] = 0;
217:         iwa3[ic] = iwa1[numinc + 1];
218:         if (iwa1[numinc + 1] > 0) iwa2[iwa1[numinc + 1]] = ic;
219:         iwa1[numinc + 1] = ic;
220:       }
221:     }
222:   }

224:   /*        End of iteration loop. */

226:   goto L30;
227: L100:

229:   /*     Invert the array list. */

231:   i__1 = *n;
232:   for (jcol = 1; jcol <= i__1; ++jcol) iwa2[list[jcol]] = jcol;
233:   i__1 = *n;
234:   for (jp = 1; jp <= i__1; ++jp) list[jp] = iwa2[jp];
235:   PetscFunctionReturn(PETSC_SUCCESS);
236: }