Actual source code: seq.c


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

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

  6: PetscErrorCode MINPACKseq(PetscInt *n, const PetscInt *indrow, const PetscInt *jpntr, const PetscInt *indcol, const PetscInt *ipntr, PetscInt *list, PetscInt *ngrp, PetscInt *maxgrp, PetscInt *iwa)
  7: {
  8:   /* System generated locals */
  9:   PetscInt i__1, i__2, i__3;

 11:   /* Local variables */
 12:   PetscInt jcol, j, ic, ip, jp, ir;

 14:   /*     Given the sparsity pattern of an m by n matrix A, this */
 15:   /*     subroutine determines a consistent partition of the */
 16:   /*     columns of A by a sequential algorithm. */
 17:   /*     A consistent partition is defined in terms of the loopless */
 18:   /*     graph G with vertices a(j), j = 1,2,...,n where a(j) is the */
 19:   /*     j-th column of A and with edge (a(i),a(j)) if and only if */
 20:   /*     columns i and j have a non-zero in the same row position. */
 21:   /*     A partition of the columns of A into groups is consistent */
 22:   /*     if the columns in any group are not adjacent in the graph G. */
 23:   /*     In graph-theory terminology, a consistent partition of the */
 24:   /*     columns of A corresponds to a coloring of the graph G. */
 25:   /*     The subroutine examines the columns in the order specified */
 26:   /*     by the array list, and assigns the current column to the */
 27:   /*     group with the smallest possible number. */
 28:   /*     Note that the value of m is not needed by seq and is */
 29:   /*     therefore not present in the subroutine statement. */
 30:   /*     The subroutine statement is */
 31:   /*       subroutine seq(n,indrow,jpntr,indcol,ipntr,list,ngrp,maxgrp, */
 32:   /*                      iwa) */
 33:   /*     where */
 34:   /*       n is a positive integer input variable set to the number */
 35:   /*         of columns of A. */
 36:   /*       indrow is an integer input array which contains the row */
 37:   /*         indices for the non-zeroes in the matrix A. */
 38:   /*       jpntr is an integer input array of length n + 1 which */
 39:   /*         specifies the locations of the row indices in indrow. */
 40:   /*         The row indices for column j are */
 41:   /*               indrow(k), k = jpntr(j),...,jpntr(j+1)-1. */
 42:   /*         Note that jpntr(n+1)-1 is then the number of non-zero */
 43:   /*         elements of the matrix A. */
 44:   /*       indcol is an integer input array which contains the */
 45:   /*         column indices for the non-zeroes in the matrix A. */
 46:   /*       ipntr is an integer input array of length m + 1 which */
 47:   /*         specifies the locations of the column indices in indcol. */
 48:   /*         The column indices for row i are */
 49:   /*               indcol(k), k = ipntr(i),...,ipntr(i+1)-1. */
 50:   /*         Note that ipntr(m+1)-1 is then the number of non-zero */
 51:   /*         elements of the matrix A. */
 52:   /*       list is an integer input array of length n which specifies */
 53:   /*         the order to be used by the sequential algorithm. */
 54:   /*         The j-th column in this order is list(j). */
 55:   /*       ngrp is an integer output array of length n which specifies */
 56:   /*         the partition of the columns of A. Column jcol belongs */
 57:   /*         to group ngrp(jcol). */
 58:   /*       maxgrp is an integer output variable which specifies the */
 59:   /*         number of groups in the partition of the columns of A. */
 60:   /*       iwa is an integer work array of length n. */
 61:   /*     Argonne National Laboratory. MINPACK Project. July 1983. */
 62:   /*     Thomas F. Coleman, Burton S. Garbow, Jorge J. More' */

 64:   PetscFunctionBegin;
 65:   /* Parameter adjustments */
 66:   --iwa;
 67:   --ngrp;
 68:   --list;
 69:   --ipntr;
 70:   --indcol;
 71:   --jpntr;
 72:   --indrow;

 74:   /* Function Body */
 75:   *maxgrp = 0;
 76:   i__1    = *n;
 77:   for (jp = 1; jp <= i__1; ++jp) {
 78:     ngrp[jp] = *n;
 79:     iwa[jp]  = 0;
 80:   }

 82:   /*     Beginning of iteration loop. */

 84:   i__1 = *n;
 85:   for (j = 1; j <= i__1; ++j) {
 86:     jcol = list[j];

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

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

 93:     i__2 = jpntr[jcol + 1] - 1;
 94:     for (jp = jpntr[jcol]; jp <= i__2; ++jp) {
 95:       ir = indrow[jp];

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

100:       i__3 = ipntr[ir + 1] - 1;
101:       for (ip = ipntr[ir]; ip <= i__3; ++ip) {
102:         ic = indcol[ip];

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

107:         iwa[ngrp[ic]] = j;
108:       }
109:     }

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

113:     i__2 = *maxgrp;
114:     for (jp = 1; jp <= i__2; ++jp) {
115:       if (iwa[jp] != j) goto L50;
116:     }
117:     ++(*maxgrp);
118:   L50:
119:     ngrp[jcol] = jp;
120:   }

122:   /*        End of iteration loop. */
123:   PetscFunctionReturn(PETSC_SUCCESS);
124: }