# spttrf.f - Man Page

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

NAG Ltd.

Definition at line 90 of file spttrf.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page spttrf(3) is an alias of spttrf.f(3).

Tue Nov 28 2023 12:08:42 Version 3.12.0 LAPACK