# dpttrf.f - Man Page

## Synopsis

### Functions/Subroutines

subroutine **dpttrf** (**N**, D, E, INFO)**DPTTRF**

## Function/Subroutine Documentation

### subroutine dpttrf (integer N, double precision, dimension( * ) D, double precision, dimension( * ) E, integer INFO)

**DPTTRF**

**Purpose:**

DPTTRF 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 DOUBLE PRECISION 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 DOUBLE PRECISION 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:**December 2016

Definition at line 93 of file dpttrf.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

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

Tue Nov 14 2017 Version 3.8.0 LAPACK