Actual source code: slo.c

      1: #define PETSCMAT_DLL

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

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

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

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

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

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

     79:     /* Function Body */
     80:     mindeg = *n;
     81:     i__1 = *n;
     82:     for (jp = 1; jp <= i__1; ++jp) {
     83:         iwa1[jp - 1] = 0;
     84:         iwa4[jp] = *n;
     85:         list[jp] = ndeg[jp];
     86:         /* Computing MIN */
     87:         i__2 = mindeg, i__3 = ndeg[jp];
     88:         mindeg = PetscMin(i__2,i__3);
     89:     }

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

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

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

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

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

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

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

    127:     /*     Beginning of iteration loop. */

    129: L30:

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

    133: L40:
    134:     jcol = iwa1[mindeg];
    135:     if (jcol > 0) {
    136:         goto L50;
    137:     }
    138:     ++mindeg;
    139:     goto L40;
    140: L50:
    141:     list[jcol] = numord;

    143:     /*        Mark the size of the largest clique */
    144:     /*        found during the ordering. */

    146:     if (mindeg + 1 == numord && !*maxclq) {
    147:         *maxclq = numord;
    148:     }

    150:     /*        Termination test. */

    152:     --numord;
    153:     if (!numord) {
    154:         goto L80;
    155:     }

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

    159:     iwa1[mindeg] = iwa3[jcol];
    160:     if (iwa3[jcol] > 0) {
    161:         iwa2[iwa3[jcol]] = 0;
    162:     }

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

    166:     iwa4[jcol] = 0;

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

    171:     i__1 = jpntr[jcol + 1] - 1;
    172:     for (jp = jpntr[jcol]; jp <= i__1; ++jp) {
    173:         ir = indrow[jp];

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

    178:         i__2 = ipntr[ir + 1] - 1;
    179:         for (ip = ipntr[ir]; ip <= i__2; ++ip) {
    180:             ic = indcol[ip];

    182:             /*              Array iwa4 marks columns which are adjacent to */
    183:             /*              column jcol. */

    185:             if (iwa4[ic] > numord) {
    186:                 iwa4[ic] = numord;

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

    190:                 numdeg = list[ic];
    191:                 --list[ic];
    192:                 /* Computing MIN */
    193:                 i__3 = mindeg, i__4 = list[ic];
    194:                 mindeg = PetscMin(i__3,i__4);

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

    198:                 if (!iwa2[ic]) {
    199:                     iwa1[numdeg] = iwa3[ic];
    200:                 } else {
    201:                     iwa3[iwa2[ic]] = iwa3[ic];
    202:                 }
    203:                 if (iwa3[ic] > 0) {
    204:                     iwa2[iwa3[ic]] = iwa2[ic];
    205:                 }

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

    209:                 iwa2[ic] = 0;
    210:                 iwa3[ic] = iwa1[numdeg - 1];
    211:                 if (iwa1[numdeg - 1] > 0) {
    212:                     iwa2[iwa1[numdeg - 1]] = ic;
    213:                 }
    214:                 iwa1[numdeg - 1] = ic;
    215:             }
    216:         }
    217:     }

    219:     /*        End of iteration loop. */

    221:     goto L30;
    222: L80:

    224:     /*     Invert the array list. */

    226:     i__1 = *n;
    227:     for (jcol = 1; jcol <= i__1; ++jcol) {
    228:         iwa2[list[jcol]] = jcol;
    229:     }
    230:     i__1 = *n;
    231:     for (jp = 1; jp <= i__1; ++jp) {
    232:         list[jp] = iwa2[jp];
    233:     }
    234:     return(0);
    235: }