spttrf (3) - Linux Manuals

NAME

spttrf.f -

SYNOPSIS

Functions/Subroutines

subroutine spttrf (N, D, E, INFO)
SPTTRF

Function/Subroutine Documentation

subroutine spttrf (integerN, real, dimension( * )D, real, dimension( * )E, integerINFO)

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

Definition at line 92 of file spttrf.f.

Author

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