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

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

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

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

 14: /*     subroutine degr */
 15: /*     Given the sparsity pattern of an m by n matrix A, */
 16: /*     this subroutine determines the degree sequence for */
 17: /*     the intersection graph of the columns of A. */
 18: /*     In graph-theory terminology, the intersection graph of */
 19: /*     the columns of A is the loopless graph G with vertices */
 20: /*     a(j), j = 1,2,...,n where a(j) is the j-th column of A */
 21: /*     and with edge (a(i),a(j)) if and only if columns i and j */
 22: /*     have a non-zero in the same row position. */
 23: /*     Note that the value of m is not needed by degr and is */
 24: /*     therefore not present in the subroutine statement. */
 25: /*     The subroutine statement is */
 26: /*       subroutine degr(n,indrow,jpntr,indcol,ipntr,ndeg,iwa) */
 27: /*     where */
 28: /*       n is a positive integer input variable set to the number */
 29: /*         of columns of A. */
 30: /*       indrow is an integer input array which contains the row */
 31: /*         indices for the non-zeroes in the matrix A. */
 32: /*       jpntr is an integer input array of length n + 1 which */
 33: /*         specifies the locations of the row indices in indrow. */
 34: /*         The row indices for column j are */
 35: /*               indrow(k), k = jpntr(j),...,jpntr(j+1)-1. */
 36: /*         Note that jpntr(n+1)-1 is then the number of non-zero */
 37: /*         elements of the matrix A. */
 38: /*       indcol is an integer input array which contains the */
 39: /*         column indices for the non-zeroes in the matrix A. */
 40: /*       ipntr is an integer input array of length m + 1 which */
 41: /*         specifies the locations of the column indices in indcol. */
 42: /*         The column indices for row i are */
 43: /*               indcol(k), k = ipntr(i),...,ipntr(i+1)-1. */
 44: /*         Note that ipntr(m+1)-1 is then the number of non-zero */
 45: /*         elements of the matrix A. */
 46: /*       ndeg is an integer output array of length n which */
 47: /*         specifies the degree sequence. The degree of the */
 48: /*         j-th column of A is ndeg(j). */
 49: /*       iwa is an integer work array of length n. */
 50: /*     Argonne National Laboratory. MINPACK Project. July 1983. */
 51: /*     Thomas F. Coleman, Burton S. Garbow, Jorge J. More' */

 54:   /* Parameter adjustments */
 55:   --iwa;
 56:   --ndeg;
 57:   --ipntr;
 58:   --indcol;
 59:   --jpntr;
 60:   --indrow;

 62:   /* Function Body */
 63:   i__1 = *n;
 64:   for (jp = 1; jp <= i__1; ++jp) {
 65:     ndeg[jp] = 0;
 66:     iwa[jp]  = 0;
 67:   }

 69: /*     Compute the degree sequence by determining the contributions */
 70: /*     to the degrees from the current(jcol) column and further */
 71: /*     columns which have not yet been considered. */

 73:   i__1 = *n;
 74:   for (jcol = 2; jcol <= i__1; ++jcol) {
 75:     iwa[jcol] = *n;

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

 80:     i__2 = jpntr[jcol + 1] - 1;
 81:     for (jp = jpntr[jcol]; jp <= i__2; ++jp) {
 82:       ir = indrow[jp];

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

 87:       i__3 = ipntr[ir + 1] - 1;
 88:       for (ip = ipntr[ir]; ip <= i__3; ++ip) {
 89:         ic = indcol[ip];

 91: /*              Array iwa marks columns which have contributed to */
 92: /*              the degree count of column jcol. Update the degree */
 93: /*              counts of these columns as well as column jcol. */

 95:         if (iwa[ic] < jcol) {
 96:           iwa[ic] = jcol;
 97:           ++ndeg[ic];
 98:           ++ndeg[jcol];
 99:         }
100:       }
101:     }
102:   }
103:   return(0);
104: }