Date: 2016-07-24T16:58:42+00:00

Actual source code: slo.c
petsc-3.7.3 2016-07-24
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      2: /* slo.f -- translated by f2c (version of 25 March 1992  12:58:56).*/

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

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

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

     17: /*     Given the sparsity pattern of an m by n matrix A, this */
     18: /*     subroutine determines the smallest-last ordering of the */
     19: /*     columns of A. */
     20: /*     The smallest-last ordering is defined for the loopless */
     21: /*     graph G with vertices a(j), j = 1,2,...,n where a(j) is the */
     22: /*     j-th column of A and with edge (a(i),a(j)) if and only if */
     23: /*     columns i and j have a non-zero in the same row position. */
     24: /*     The smallest-last ordering is determined recursively by */
     25: /*     letting list(k), k = n,...,1 be a column with least degree */
     26: /*     in the subgraph spanned by the un-ordered columns. */
     27: /*     Note that the value of m is not needed by slo and is */
     28: /*     therefore not present in the subroutine statement. */
     29: /*     The subroutine statement is */
     30: /*       subroutine slo(n,indrow,jpntr,indcol,ipntr,ndeg,list, */
     31: /*                      maxclq,iwa1,iwa2,iwa3,iwa4) */
     32: /*     where */
     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 smallest-last 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: /*       FORTRAN-supplied ... min */
     62: /*     Argonne National Laboratory. MINPACK Project. August 1984. */
     63: /*     Thomas F. Coleman, Burton S. Garbow, Jorge J. More' */

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

     77:   /* Function Body */
     78:   mindeg = *n;
     79:   i__1   = *n;
     80:   for (jp = 1; jp <= i__1; ++jp) {
     81:     iwa1[jp - 1] = 0;
     82:     iwa4[jp]     = *n;
     83:     list[jp]     = ndeg[jp];
     84:     /* Computing MIN */
     85:     i__2   = mindeg, i__3 = ndeg[jp];
     86:     mindeg = PetscMin(i__2,i__3);
     87:   }

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

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

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

     99:   /*     iwa2(ic) is the column before ic in the degree list */
    100:   /*     unless iwa2(ic) = 0. In this case ic is the first */
    101:   /*     column in this degree list. */

    103:   /*     iwa3(ic) is the column after ic in the degree list */
    104:   /*     unless iwa3(ic) = 0. In this case ic is the last */
    105:   /*     column in this degree list. */

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

    112:   i__1 = *n;
    113:   for (jp = 1; jp <= i__1; ++jp) {
    114:     numdeg   = ndeg[jp];
    115:     iwa2[jp] = 0;
    116:     iwa3[jp] = iwa1[numdeg];
    117:     if (iwa1[numdeg] > 0) {
    118:       iwa2[iwa1[numdeg]] = jp;
    119:     }
    120:     iwa1[numdeg] = jp;
    121:   }
    122:   *maxclq = 0;
    123:   numord  = *n;

    125:   /*     Beginning of iteration loop. */

    127: L30:

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

    131: L40:
    132:   jcol = iwa1[mindeg];
    133:   if (jcol > 0) goto L50;
    134:   ++mindeg;
    135:   goto L40;
    136: L50:
    137:   list[jcol] = numord;

    139:   /*        Mark the size of the largest clique */
    140:   /*        found during the ordering. */

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

    144:   /*        Termination test. */

    146:   --numord;
    147:   if (!numord) goto L80;

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

    151:   iwa1[mindeg] = iwa3[jcol];
    152:   if (iwa3[jcol] > 0) iwa2[iwa3[jcol]] = 0;

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

    156:   iwa4[jcol] = 0;

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

    161:   i__1 = jpntr[jcol + 1] - 1;
    162:   for (jp = jpntr[jcol]; jp <= i__1; ++jp) {
    163:     ir = indrow[jp];

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

    168:     i__2 = ipntr[ir + 1] - 1;
    169:     for (ip = ipntr[ir]; ip <= i__2; ++ip) {
    170:       ic = indcol[ip];

    172:       /*              Array iwa4 marks columns which are adjacent to */
    173:       /*              column jcol. */

    175:       if (iwa4[ic] > numord) {
    176:         iwa4[ic] = numord;

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

    180:         numdeg = list[ic];
    181:         --list[ic];
    182:         /* Computing MIN */
    183:         i__3   = mindeg, i__4 = list[ic];
    184:         mindeg = PetscMin(i__3,i__4);

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

    188:         if (!iwa2[ic]) iwa1[numdeg] = iwa3[ic];
    189:         else iwa3[iwa2[ic]] = iwa3[ic];

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

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

    195:         iwa2[ic] = 0;
    196:         iwa3[ic] = iwa1[numdeg - 1];
    197:         if (iwa1[numdeg - 1] > 0) iwa2[iwa1[numdeg - 1]] = ic;
    198:         iwa1[numdeg - 1] = ic;
    199:       }
    200:     }
    201:   }

    203:   /*        End of iteration loop. */

    205:   goto L30;
    206: L80:

    208:   /*     Invert the array list. */

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

    213:   i__1 = *n;
    214:   for (jp = 1; jp <= i__1; ++jp) list[jp] = iwa2[jp];
    215:   return(0);
    216: }