Actual source code: seq.c

      1: #define PETSCMAT_DLL

      3: /* seq.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 MINPACKseq(PetscInt *n,PetscInt *indrow,PetscInt *jpntr,PetscInt *indcol,PetscInt *ipntr,PetscInt *list,PetscInt *ngrp,
     11:                           PetscInt *maxgrp,PetscInt *iwa)
     12: {
     13:     /* System generated locals */
     14:     PetscInt i__1, i__2, i__3;

     16:     /* Local variables */
     17:     PetscInt jcol, j, ic, ip, jp, ir;

     19: /*     Given the sparsity pattern of an m by n matrix A, this */
     20: /*     subroutine determines a consistent partition of the */
     21: /*     columns of A by a sequential algorithm. */
     22: /*     A consistent partition is defined in terms of 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: /*     A partition of the columns of A into groups is consistent */
     27: /*     if the columns in any group are not adjacent in the graph G. */
     28: /*     In graph-theory terminology, a consistent partition of the */
     29: /*     columns of A corresponds to a coloring of the graph G. */
     30: /*     The subroutine examines the columns in the order specified */
     31: /*     by the array list, and assigns the current column to the */
     32: /*     group with the smallest possible number. */
     33: /*     Note that the value of m is not needed by seq and is */
     34: /*     therefore not present in the subroutine statement. */
     35: /*     The subroutine statement is */
     36: /*       subroutine seq(n,indrow,jpntr,indcol,ipntr,list,ngrp,maxgrp, */
     37: /*                      iwa) */
     38: /*     where */
     39: /*       n is a positive integer input variable set to the number */
     40: /*         of columns of A. */
     41: /*       indrow is an integer input array which contains the row */
     42: /*         indices for the non-zeroes in the matrix A. */
     43: /*       jpntr is an integer input array of length n + 1 which */
     44: /*         specifies the locations of the row indices in indrow. */
     45: /*         The row indices for column j are */
     46: /*               indrow(k), k = jpntr(j),...,jpntr(j+1)-1. */
     47: /*         Note that jpntr(n+1)-1 is then the number of non-zero */
     48: /*         elements of the matrix A. */
     49: /*       indcol is an integer input array which contains the */
     50: /*         column indices for the non-zeroes in the matrix A. */
     51: /*       ipntr is an integer input array of length m + 1 which */
     52: /*         specifies the locations of the column indices in indcol. */
     53: /*         The column indices for row i are */
     54: /*               indcol(k), k = ipntr(i),...,ipntr(i+1)-1. */
     55: /*         Note that ipntr(m+1)-1 is then the number of non-zero */
     56: /*         elements of the matrix A. */
     57: /*       list is an integer input array of length n which specifies */
     58: /*         the order to be used by the sequential algorithm. */
     59: /*         The j-th column in this order is list(j). */
     60: /*       ngrp is an integer output array of length n which specifies */
     61: /*         the partition of the columns of A. Column jcol belongs */
     62: /*         to group ngrp(jcol). */
     63: /*       maxgrp is an integer output variable which specifies the */
     64: /*         number of groups in the partition of the columns of A. */
     65: /*       iwa is an integer work array of length n. */
     66: /*     Argonne National Laboratory. MINPACK Project. July 1983. */
     67: /*     Thomas F. Coleman, Burton S. Garbow, Jorge J. More' */

     70:     /* Parameter adjustments */
     71:     --iwa;
     72:     --ngrp;
     73:     --list;
     74:     --ipntr;
     75:     --indcol;
     76:     --jpntr;
     77:     --indrow;

     79:     /* Function Body */
     80:     *maxgrp = 0;
     81:     i__1 = *n;
     82:     for (jp = 1; jp <= i__1; ++jp) {
     83:         ngrp[jp] = *n;
     84:         iwa[jp] = 0;
     85:     }

     87:     /*     Beginning of iteration loop. */

     89:     i__1 = *n;
     90:     for (j = 1; j <= i__1; ++j) {
     91:         jcol = list[j];

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

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

     98:         i__2 = jpntr[jcol + 1] - 1;
     99:         for (jp = jpntr[jcol]; jp <= i__2; ++jp) {
    100:             ir = indrow[jp];

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

    105:             i__3 = ipntr[ir + 1] - 1;
    106:             for (ip = ipntr[ir]; ip <= i__3; ++ip) {
    107:                 ic = indcol[ip];

    109:                 /*              Array iwa marks the group numbers of the */
    110:                 /*              columns which are adjacent to column jcol. */

    112:                 iwa[ngrp[ic]] = j;
    113:             }
    114:         }

    116:         /*        Assign the smallest un-marked group number to jcol. */

    118:         i__2 = *maxgrp;
    119:         for (jp = 1; jp <= i__2; ++jp) {
    120:             if (iwa[jp] != j) {
    121:                 goto L50;
    122:             }
    123:         }
    124:         ++(*maxgrp);
    125: L50:
    126:         ngrp[jcol] = jp;
    127:     }

    129:     /*        End of iteration loop. */

    131:     return(0);
    132: }