# spttrf.f man page

spttrf.f —

## Synopsis

### Functions/Subroutines

subroutinespttrf(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

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

spttrf(3) is an alias of spttrf.f(3).