Date: 2022-03-04T17:38:21+00:00

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,
      8:                PetscInt *list,PetscInt *maxclq, PetscInt *iwa1, PetscInt *iwa2, PetscInt *iwa3, PetscInt *iwa4)
      9: {
     10:   /* System generated locals */
     11:   PetscInt i__1, i__2, i__3, i__4;

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

     16: /*     Given the sparsity pattern of an m by n matrix A, this */
     17: /*     subroutine determines an incidence-degree ordering of the */
     18: /*     columns of A. */
     19: /*     The incidence-degree ordering is defined for the loopless */
     20: /*     graph G with vertices a(j), j = 1,2,...,n where a(j) is the */
     21: /*     j-th column of A and with edge (a(i),a(j)) if and only if */
     22: /*     columns i and j have a non-zero in the same row position. */
     23: /*     The incidence-degree ordering is determined recursively by */
     24: /*     letting list(k), k = 1,...,n be a column with maximal */
     25: /*     incidence to the subgraph spanned by the ordered columns. */
     26: /*     Among all the columns of maximal incidence, ido chooses a */
     27: /*     column of maximal degree. */
     28: /*     The subroutine statement is */
     29: /*       subroutine ido(m,n,indrow,jpntr,indcol,ipntr,ndeg,list, */
     30: /*                      maxclq,iwa1,iwa2,iwa3,iwa4) */
     31: /*     where */
     32: /*       m is a positive integer input variable set to the number */
     33: /*         of rows of A. */
     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 incidence-degree 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: /*       MINPACK-supplied ... numsrt */
     63: /*       FORTRAN-supplied ... max */
     64: /*     Argonne National Laboratory. MINPACK Project. August 1984. */
     65: /*     Thomas F. Coleman, Burton S. Garbow, Jorge J. More' */

     67: /*     Sort the degree sequence. */

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

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

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

    104:   maxinc = 0;
    105:   for (jp = *n; jp >= 1; --jp) {
    106:     ic            = iwa4[jp];
    107:     iwa1[*n - jp] = 0;
    108:     iwa2[ic]      = 0;
    109:     iwa3[ic]      = iwa1[0];
    110:     if (iwa1[0] > 0) iwa2[iwa1[0]] = ic;
    111:     iwa1[0]  = ic;
    112:     iwa4[jp] = 0;
    113:     list[jp] = 0;
    114:   }

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

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

    130: /*     Beginning of iteration loop. */

    132: L30:

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

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

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

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

    163: /*        Termination test. */

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

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

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

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

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

    177:   iwa4[jcol] = *n;

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

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

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

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

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

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

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

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

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

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

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

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

    217:         iwa2[ic] = 0;
    218:         iwa3[ic] = iwa1[numinc + 1];
    219:         if (iwa1[numinc + 1] > 0) iwa2[iwa1[numinc + 1]] = ic;
    220:         iwa1[numinc + 1] = ic;
    221:       }
    222:     }
    223:   }

    225: /*        End of iteration loop. */

    227:   goto L30;
    228: L100:

    230: /*     Invert the array list. */

    232:   i__1 = *n;
    233:   for (jcol = 1; jcol <= i__1; ++jcol) iwa2[list[jcol]] = jcol;
    234:   i__1 = *n;
    235:   for (jp = 1; jp <= i__1; ++jp) list[jp] = iwa2[jp];
    236:   return(0);
    237: }