Actual source code: slo.c

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

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

      5: PetscErrorCode MINPACKslo(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)
      6: {
      7:   /* System generated locals */
      8:   PetscInt i__1, i__2, i__3, i__4;

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

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

     61:   PetscFunctionBegin;
     62:   /* Parameter adjustments */
     63:   --iwa4;
     64:   --iwa3;
     65:   --iwa2;
     66:   --list;
     67:   --ndeg;
     68:   --ipntr;
     69:   --indcol;
     70:   --jpntr;
     71:   --indrow;

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

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

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

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

     96:   /*     iwa2(ic) is the column before ic in the degree list */
     97:   /*     unless iwa2(ic) = 0. In this case ic is the first */
     98:   /*     column in this degree list. */

    100:   /*     iwa3(ic) is the column after ic in the degree list */
    101:   /*     unless iwa3(ic) = 0. In this case ic is the last */
    102:   /*     column in this degree list. */

    104:   /*     If ic is an un-ordered column, then list(ic) is the */
    105:   /*     degree of ic in the graph induced by the un-ordered */
    106:   /*     columns. If jcol is an ordered column, then list(jcol) */
    107:   /*     is the smallest-last order of column jcol. */

    109:   i__1 = *n;
    110:   for (jp = 1; jp <= i__1; ++jp) {
    111:     numdeg   = ndeg[jp];
    112:     iwa2[jp] = 0;
    113:     iwa3[jp] = iwa1[numdeg];
    114:     if (iwa1[numdeg] > 0) iwa2[iwa1[numdeg]] = jp;
    115:     iwa1[numdeg] = jp;
    116:   }
    117:   *maxclq = 0;
    118:   numord  = *n;

    120:   /*     Beginning of iteration loop. */

    122: L30:

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

    126: L40:
    127:   jcol = iwa1[mindeg];
    128:   if (jcol > 0) goto L50;
    129:   ++mindeg;
    130:   goto L40;
    131: L50:
    132:   list[jcol] = numord;

    134:   /*        Mark the size of the largest clique */
    135:   /*        found during the ordering. */

    137:   if (mindeg + 1 == numord && !*maxclq) *maxclq = numord;

    139:   /*        Termination test. */

    141:   --numord;
    142:   if (!numord) goto L80;

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

    146:   iwa1[mindeg] = iwa3[jcol];
    147:   if (iwa3[jcol] > 0) iwa2[iwa3[jcol]] = 0;

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

    151:   iwa4[jcol] = 0;

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

    156:   i__1 = jpntr[jcol + 1] - 1;
    157:   for (jp = jpntr[jcol]; jp <= i__1; ++jp) {
    158:     ir = indrow[jp];

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

    163:     i__2 = ipntr[ir + 1] - 1;
    164:     for (ip = ipntr[ir]; ip <= i__2; ++ip) {
    165:       ic = indcol[ip];

    167:       /*              Array iwa4 marks columns which are adjacent to */
    168:       /*              column jcol. */

    170:       if (iwa4[ic] > numord) {
    171:         iwa4[ic] = numord;

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

    175:         numdeg = list[ic];
    176:         --list[ic];
    177:         /* Computing MIN */
    178:         i__3   = mindeg;
    179:         i__4   = list[ic];
    180:         mindeg = PetscMin(i__3, i__4);

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

    184:         if (!iwa2[ic]) iwa1[numdeg] = iwa3[ic];
    185:         else iwa3[iwa2[ic]] = iwa3[ic];

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

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

    191:         iwa2[ic] = 0;
    192:         iwa3[ic] = iwa1[numdeg - 1];
    193:         if (iwa1[numdeg - 1] > 0) iwa2[iwa1[numdeg - 1]] = ic;
    194:         iwa1[numdeg - 1] = ic;
    195:       }
    196:     }
    197:   }

    199:   /*        End of iteration loop. */

    201:   goto L30;
    202: L80:

    204:   /*     Invert the array list. */

    206:   i__1 = *n;
    207:   for (jcol = 1; jcol <= i__1; ++jcol) iwa2[list[jcol]] = jcol;

    209:   i__1 = *n;
    210:   for (jp = 1; jp <= i__1; ++jp) list[jp] = iwa2[jp];
    211:   PetscFunctionReturn(PETSC_SUCCESS);
    212: }