Actual source code: ido.c
petsc-3.7.1 2016-05-15
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      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;

      9: PetscErrorCode MINPACKido(PetscInt *m,PetscInt * n,const PetscInt * indrow,const PetscInt * jpntr,const PetscInt * indcol,const PetscInt * ipntr,PetscInt * ndeg,
     10:                PetscInt *list,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 = 0, ncomp = 0, ic, ip, jp, ir, maxinc, numinc, numord, maxlst, numwgt, numlst;

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

     69: /*     Sort the degree sequence. */

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

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

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

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

    118: /*     Determine the maximal search length for the list */
    119: /*     of columns of maximal incidence. */

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

    132: /*     Beginning of iteration loop. */

    134: L30:

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

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

    158: /*        Update the size of the largest clique */
    159: /*        found during the ordering. */

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

    165: /*        Termination test. */

    167:   ++numord;
    168:   if (numord > *n) goto L100;

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

    172:   if (!iwa2[jcol]) iwa1[maxinc] = iwa3[jcol];
    173:   else iwa3[iwa2[jcol]] = iwa3[jcol];

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

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

    179:   iwa4[jcol] = *n;

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

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

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

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

    195: /*              Array iwa4 marks columns which are adjacent to */
    196: /*              column jcol. */

    198:       if (iwa4[ic] < numord) {
    199:         iwa4[ic] = numord;

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

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

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

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

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

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

    218:         iwa2[ic] = 0;
    219:         iwa3[ic] = iwa1[numinc + 1];
    220:         if (iwa1[numinc + 1] > 0) iwa2[iwa1[numinc + 1]] = ic;
    221:         iwa1[numinc + 1] = ic;
    222:       }
    223:     }
    224:   }

    226: /*        End of iteration loop. */

    228:   goto L30;
    229: L100:

    231: /*     Invert the array list. */

    233:   i__1 = *n;
    234:   for (jcol = 1; jcol <= i__1; ++jcol) iwa2[list[jcol]] = jcol;
    235:   i__1 = *n;
    236:   for (jp = 1; jp <= i__1; ++jp) list[jp] = iwa2[jp];
    237:   return(0);
    238: }