NAME

       spttrf.f -

SYNOPSIS

   Functions/Subroutines
       subroutine spttrf (N, D, E, INFO)
           SPTTRF

Function/Subroutine Documentation

   subroutine spttrf (integer N, real, dimension( * ) D, real, dimension( * ) E, integer INFO)
       SPTTRF

       Purpose:

            SPTTRF computes the L*D*L**T factorization of a real symmetric
            positive definite tridiagonal matrix A.  The factorization may also
            be regarded as having the form A = U**T*D*U.

       Parameters:
           N

                     N is INTEGER
                     The order of the matrix A.  N >= 0.

           D

                     D is REAL array, dimension (N)
                     On entry, the n diagonal elements of the tridiagonal matrix
                     A.  On exit, the n diagonal elements of the diagonal matrix
                     D from the L*D*L**T factorization of A.

           E

                     E is REAL array, dimension (N-1)
                     On entry, the (n-1) subdiagonal elements of the tridiagonal
                     matrix A.  On exit, the (n-1) subdiagonal elements of the
                     unit bidiagonal factor L from the L*D*L**T factorization of A.
                     E can also be regarded as the superdiagonal of the unit
                     bidiagonal factor U from the U**T*D*U factorization of A.

           INFO

                     INFO is INTEGER
                     = 0: successful exit
                     < 0: if INFO = -k, the k-th argument had an illegal 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 factorization was
                          completed, but D(N) <= 0.

       Author:
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Date:
           November 2011

Author

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