# dpotrf2.f - Man Page

SRC/dpotrf2.f

## Synopsis

### Functions/Subroutines

recursive subroutine dpotrf2 (uplo, n, a, lda, info)
DPOTRF2

## Function/Subroutine Documentation

### recursive subroutine dpotrf2 (character uplo, integer n, double precision, dimension( lda, * ) a, integer lda, integer info)

DPOTRF2

Purpose:

DPOTRF2 computes the Cholesky factorization of a real symmetric
positive definite matrix A using the recursive algorithm.

The factorization has the form
A = U**T * U,  if UPLO = 'U', or
A = L  * L**T,  if UPLO = 'L',
where U is an upper triangular matrix and L is lower triangular.

This is the recursive version of the algorithm. It divides
the matrix into four submatrices:

[  A11 | A12  ]  where A11 is n1 by n1 and A22 is n2 by n2
A = [ -----|----- ]  with n1 = n/2
[  A21 | A22  ]       n2 = n-n1

The subroutine calls itself to factor A11. Update and scale A21
or A12, update A22 then calls itself to factor A22.
Parameters

UPLO

UPLO is CHARACTER*1
= 'U':  Upper triangle of A is stored;
= 'L':  Lower triangle of A is stored.

N

N is INTEGER
The order of the matrix A.  N >= 0.

A

A is DOUBLE PRECISION array, dimension (LDA,N)
On entry, the symmetric matrix A.  If UPLO = 'U', the leading
N-by-N upper triangular part of A contains the upper
triangular part of the matrix A, and the strictly lower
triangular part of A is not referenced.  If UPLO = 'L', the
leading N-by-N lower triangular part of A contains the lower
triangular part of the matrix A, and the strictly upper
triangular part of A is not referenced.

On exit, if INFO = 0, the factor U or L from the Cholesky
factorization A = U**T*U or A = L*L**T.

LDA

LDA is INTEGER
The leading dimension of the array A.  LDA >= max(1,N).

INFO

INFO is INTEGER
= 0:  successful exit
< 0:  if INFO = -i, the i-th argument had an illegal value
> 0:  if INFO = i, the leading principal minor of order i
is not positive, and the factorization could not be
completed.
Author

Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Definition at line 105 of file dpotrf2.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dpotrf2(3) is an alias of dpotrf2.f(3).

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