Actual source code: ido.c

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

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

      7: static PetscInt c_n1 = -1;

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

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

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

     71: /*     Sort the degree sequence. */

     74:     /* Parameter adjustments */
     75:     --iwa4;
     76:     --iwa3;
     77:     --iwa2;
     78:     --list;
     79:     --ndeg;
     80:     --ipntr;
     81:     --indcol;
     82:     --jpntr;
     83:     --indrow;

     85:     /* Function Body */
     86:     i__1 = *n - 1;
     87:     MINPACKnumsrt(n, &i__1, &ndeg[1], &c_n1, &iwa4[1], &iwa2[1], &iwa3[1]);

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

    108:     maxinc = 0;
    109:     for (jp = *n; jp >= 1; --jp) {
    110:         ic = iwa4[jp];
    111:         iwa1[*n - jp] = 0;
    112:         iwa2[ic] = 0;
    113:         iwa3[ic] = iwa1[0];
    114:         if (iwa1[0] > 0) {
    115:             iwa2[iwa1[0]] = ic;
    116:         }
    117:         iwa1[0] = ic;
    118:         iwa4[jp] = 0;
    119:         list[jp] = 0;
    120:     }

    122: /*     Determine the maximal search length for the list */
    123: /*     of columns of maximal incidence. */

    125:     maxlst = 0;
    126:     i__1 = *m;
    127:     for (ir = 1; ir <= i__1; ++ir) {
    128: /* Computing 2nd power */
    129:         i__2 = ipntr[ir + 1] - ipntr[ir];
    130:         maxlst += i__2 * i__2;
    131:     }
    132:     maxlst /= *n;
    133:     *maxclq = 0;
    134:     numord = 1;

    136: /*     Beginning of iteration loop. */

    138: L30:

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

    143: L40:
    144:     jp = iwa1[maxinc];
    145:     if (jp > 0) {
    146:         goto L50;
    147:     }
    148:     --maxinc;
    149:     goto L40;
    150: L50:
    151:     numwgt = -1;
    152:     i__1 = maxlst;
    153:     for (numlst = 1; numlst <= i__1; ++numlst) {
    154:         if (ndeg[jp] > numwgt) {
    155:             numwgt = ndeg[jp];
    156:             jcol = jp;
    157:         }
    158:         jp = iwa3[jp];
    159:         if (jp <= 0) {
    160:             goto L70;
    161:         }
    162:     }
    163: L70:
    164:     list[jcol] = numord;

    166: /*        Update the size of the largest clique */
    167: /*        found during the ordering. */

    169:     if (!maxinc) {
    170:         ncomp = 0;
    171:     }
    172:     ++ncomp;
    173:     if (maxinc + 1 == ncomp) {
    174:         *maxclq = PetscMax(*maxclq,ncomp);
    175:     }

    177: /*        Termination test. */

    179:     ++numord;
    180:     if (numord > *n) {
    181:         goto L100;
    182:     }

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

    186:     if (!iwa2[jcol]) {
    187:         iwa1[maxinc] = iwa3[jcol];
    188:     } else {
    189:         iwa3[iwa2[jcol]] = iwa3[jcol];
    190:     }
    191:     if (iwa3[jcol] > 0) {
    192:         iwa2[iwa3[jcol]] = iwa2[jcol];
    193:     }

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

    197:     iwa4[jcol] = *n;

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

    202:     i__1 = jpntr[jcol + 1] - 1;
    203:     for (jp = jpntr[jcol]; jp <= i__1; ++jp) {
    204:         ir = indrow[jp];

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

    209:         i__2 = ipntr[ir + 1] - 1;
    210:         for (ip = ipntr[ir]; ip <= i__2; ++ip) {
    211:             ic = indcol[ip];

    213: /*              Array iwa4 marks columns which are adjacent to */
    214: /*              column jcol. */

    216:             if (iwa4[ic] < numord) {
    217:                 iwa4[ic] = numord;

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

    221:                 numinc = list[ic];
    222:                 ++list[ic];
    223: /* Computing MAX */
    224:                 i__3 = maxinc, i__4 = list[ic];
    225:                 maxinc = PetscMax(i__3,i__4);

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

    229:                 if (!iwa2[ic]) {
    230:                     iwa1[numinc] = iwa3[ic];
    231:                 } else {
    232:                     iwa3[iwa2[ic]] = iwa3[ic];
    233:                 }
    234:                 if (iwa3[ic] > 0) {
    235:                     iwa2[iwa3[ic]] = iwa2[ic];
    236:                 }

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

    240:                 iwa2[ic] = 0;
    241:                 iwa3[ic] = iwa1[numinc + 1];
    242:                 if (iwa1[numinc + 1] > 0) {
    243:                     iwa2[iwa1[numinc + 1]] = ic;
    244:                 }
    245:                 iwa1[numinc + 1] = ic;
    246:             }
    247:         }
    248:     }

    250: /*        End of iteration loop. */

    252:     goto L30;
    253: L100:

    255: /*     Invert the array list. */

    257:     i__1 = *n;
    258:     for (jcol = 1; jcol <= i__1; ++jcol) {
    259:         iwa2[list[jcol]] = jcol;
    260:     }
    261:     i__1 = *n;
    262:     for (jp = 1; jp <= i__1; ++jp) {
    263:         list[jp] = iwa2[jp];
    264:     }
    265:     return(0);
    266: }