Contents


NAME

     cpttrf - compute the L*D*L' factorization of a complex  Her-
     mitian positive definite tridiagonal matrix A

SYNOPSIS

     SUBROUTINE CPTTRF(N, D, E, INFO)

     COMPLEX E(*)
     INTEGER N, INFO
     REAL D(*)

     SUBROUTINE CPTTRF_64(N, D, E, INFO)

     COMPLEX E(*)
     INTEGER*8 N, INFO
     REAL D(*)

  F95 INTERFACE
     SUBROUTINE PTTRF([N], D, E, [INFO])

     COMPLEX, DIMENSION(:) :: E
     INTEGER :: N, INFO
     REAL, DIMENSION(:) :: D

     SUBROUTINE PTTRF_64([N], D, E, [INFO])

     COMPLEX, DIMENSION(:) :: E
     INTEGER(8) :: N, INFO
     REAL, DIMENSION(:) :: D

  C INTERFACE
     #include <sunperf.h>

     void cpttrf(int n, float *d, complex *e, int *info);

     void cpttrf_64(long n, float *d, complex *e, long *info);

PURPOSE

     cpttrf computes the L*D*L' factorization of a complex Hermi-
     tian positive definite tridiagonal matrix A.  The factoriza-
     tion may also be regarded as having the form A = U'*D*U.

ARGUMENTS

     N (input) The order of the matrix A.  N >= 0.
     D (input/output)
               On entry, the n diagonal elements of the tridiago-
               nal matrix A.  On exit, the n diagonal elements of
               the diagonal matrix D from the  L*D*L'  factoriza-
               tion of A.

     E (input/output)
               On entry, the (n-1) subdiagonal  elements  of  the
               tridiagonal matrix A.  On exit, the (n-1) subdiag-
               onal elements of the unit bidiagonal factor L from
               the  L*D*L'  factorization  of  A.   E can also be
               regarded as the superdiagonal of the unit bidiago-
               nal factor U from the U'*D*U factorization of A.

     INFO (output)
               = 0: successful exit
               < 0: if INFO = -k, the k-th argument had an  ille-
               gal value
               > 0: if INFO = k, the leading minor of order k  is
               not positive definite; if k < N, the factorization
               could not be completed, while if k = N,  the  fac-
               torization was completed, but D(N) = 0.