SRC/spttrf.f(3)

NAME
SRC/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 principal minor of order k
                   is not positive; 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.

Definition at line 90 of file spttrf.f.

Author

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