Actual source code: degr.c

  1: #define PETSCMAT_DLL

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

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

  9: PetscErrorCode MINPACKdegr(PetscInt *n,PetscInt * indrow,PetscInt * jpntr,PetscInt * indcol,PetscInt * ipntr,PetscInt * ndeg,PetscInt * iwa)
 10: {
 11:     /* System generated locals */
 12:     PetscInt i__1, i__2, i__3;

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

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

 57:     /* Parameter adjustments */
 58:     --iwa;
 59:     --ndeg;
 60:     --ipntr;
 61:     --indcol;
 62:     --jpntr;
 63:     --indrow;

 65:     /* Function Body */
 66:     i__1 = *n;
 67:     for (jp = 1; jp <= i__1; ++jp) {
 68:         ndeg[jp] = 0;
 69:         iwa[jp] = 0;
 70:     }

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

 76:     i__1 = *n;
 77:     for (jcol = 2; jcol <= i__1; ++jcol) {
 78:         iwa[jcol] = *n;

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

 83:         i__2 = jpntr[jcol + 1] - 1;
 84:         for (jp = jpntr[jcol]; jp <= i__2; ++jp) {
 85:             ir = indrow[jp];

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

 90:             i__3 = ipntr[ir + 1] - 1;
 91:             for (ip = ipntr[ir]; ip <= i__3; ++ip) {
 92:                 ic = indcol[ip];

 94: /*              Array iwa marks columns which have contributed to */
 95: /*              the degree count of column jcol. Update the degree */
 96: /*              counts of these columns as well as column jcol. */

 98:                 if (iwa[ic] < jcol) {
 99:                     iwa[ic] = jcol;
100:                     ++ndeg[ic];
101:                     ++ndeg[jcol];
102:                 }
103:             }
104:         }
105:     }
106:     return(0);
107: }