# VARIANTS_cholesky_TOP_dpotrf.f - Man Page

dpotrf.f

## Synopsis

### Functions/Subroutines

subroutine **dpotrf** (UPLO, **N**, A, **LDA**, INFO)**DPOTRF** VARIANT: top-looking block version of the algorithm, calling Level 3 BLAS.

## Function/Subroutine Documentation

### subroutine dpotrf (character UPLO, integer N, double precision, dimension( lda, * ) A, integer LDA, integer INFO)

**DPOTRF** VARIANT: top-looking block version of the algorithm, calling Level 3 BLAS. **Purpose:**

DPOTRF computes the Cholesky factorization of a real symmetric positive definite matrix A. 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 top-looking block version of the algorithm, calling Level 3 BLAS.

**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 minor of order i is not positive definite, and the factorization could not be completed.

**Author:**Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**December 2016

Definition at line 102 of file VARIANTS/cholesky/TOP/dpotrf.f.

## Author

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## Info

Tue Nov 14 2017 Version 3.8.0 LAPACK