# lauu2 - Man Page

lauu2: triangular multiply: U^H U, level 2

## Synopsis

### Functions

subroutine clauu2 (uplo, n, a, lda, info)
CLAUU2 computes the product UUH or LHL, where U and L are upper or lower triangular matrices (unblocked algorithm).
subroutine dlauu2 (uplo, n, a, lda, info)
DLAUU2 computes the product UUH or LHL, where U and L are upper or lower triangular matrices (unblocked algorithm).
subroutine slauu2 (uplo, n, a, lda, info)
SLAUU2 computes the product UUH or LHL, where U and L are upper or lower triangular matrices (unblocked algorithm).
subroutine zlauu2 (uplo, n, a, lda, info)
ZLAUU2 computes the product UUH or LHL, where U and L are upper or lower triangular matrices (unblocked algorithm).

## Function Documentation

### subroutine clauu2 (character uplo, integer n, complex, dimension( lda, * ) a, integer lda, integer info)

CLAUU2 computes the product UUH or LHL, where U and L are upper or lower triangular matrices (unblocked algorithm).

Purpose:

``` CLAUU2 computes the product U * U**H or L**H * L, where the triangular
factor U or L is stored in the upper or lower triangular part of
the array A.

If UPLO = 'U' or 'u' then the upper triangle of the result is stored,
overwriting the factor U in A.
If UPLO = 'L' or 'l' then the lower triangle of the result is stored,
overwriting the factor L in A.

This is the unblocked form of the algorithm, calling Level 2 BLAS.```
Parameters

UPLO

```          UPLO is CHARACTER*1
Specifies whether the triangular factor stored in the array A
is upper or lower triangular:
= 'U':  Upper triangular
= 'L':  Lower triangular```

N

```          N is INTEGER
The order of the triangular factor U or L.  N >= 0.```

A

```          A is COMPLEX array, dimension (LDA,N)
On entry, the triangular factor U or L.
On exit, if UPLO = 'U', the upper triangle of A is
overwritten with the upper triangle of the product U * U**H;
if UPLO = 'L', the lower triangle of A is overwritten with
the lower triangle of the product L**H * L.```

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 = -k, the k-th argument had an illegal value```
Author

Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Definition at line 101 of file clauu2.f.

### subroutine dlauu2 (character uplo, integer n, double precision, dimension( lda, * ) a, integer lda, integer info)

DLAUU2 computes the product UUH or LHL, where U and L are upper or lower triangular matrices (unblocked algorithm).

Purpose:

``` DLAUU2 computes the product U * U**T or L**T * L, where the triangular
factor U or L is stored in the upper or lower triangular part of
the array A.

If UPLO = 'U' or 'u' then the upper triangle of the result is stored,
overwriting the factor U in A.
If UPLO = 'L' or 'l' then the lower triangle of the result is stored,
overwriting the factor L in A.

This is the unblocked form of the algorithm, calling Level 2 BLAS.```
Parameters

UPLO

```          UPLO is CHARACTER*1
Specifies whether the triangular factor stored in the array A
is upper or lower triangular:
= 'U':  Upper triangular
= 'L':  Lower triangular```

N

```          N is INTEGER
The order of the triangular factor U or L.  N >= 0.```

A

```          A is DOUBLE PRECISION array, dimension (LDA,N)
On entry, the triangular factor U or L.
On exit, if UPLO = 'U', the upper triangle of A is
overwritten with the upper triangle of the product U * U**T;
if UPLO = 'L', the lower triangle of A is overwritten with
the lower triangle of the product L**T * L.```

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 = -k, the k-th argument had an illegal value```
Author

Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Definition at line 101 of file dlauu2.f.

### subroutine slauu2 (character uplo, integer n, real, dimension( lda, * ) a, integer lda, integer info)

SLAUU2 computes the product UUH or LHL, where U and L are upper or lower triangular matrices (unblocked algorithm).

Purpose:

``` SLAUU2 computes the product U * U**T or L**T * L, where the triangular
factor U or L is stored in the upper or lower triangular part of
the array A.

If UPLO = 'U' or 'u' then the upper triangle of the result is stored,
overwriting the factor U in A.
If UPLO = 'L' or 'l' then the lower triangle of the result is stored,
overwriting the factor L in A.

This is the unblocked form of the algorithm, calling Level 2 BLAS.```
Parameters

UPLO

```          UPLO is CHARACTER*1
Specifies whether the triangular factor stored in the array A
is upper or lower triangular:
= 'U':  Upper triangular
= 'L':  Lower triangular```

N

```          N is INTEGER
The order of the triangular factor U or L.  N >= 0.```

A

```          A is REAL array, dimension (LDA,N)
On entry, the triangular factor U or L.
On exit, if UPLO = 'U', the upper triangle of A is
overwritten with the upper triangle of the product U * U**T;
if UPLO = 'L', the lower triangle of A is overwritten with
the lower triangle of the product L**T * L.```

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 = -k, the k-th argument had an illegal value```
Author

Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Definition at line 101 of file slauu2.f.

### subroutine zlauu2 (character uplo, integer n, complex*16, dimension( lda, * ) a, integer lda, integer info)

ZLAUU2 computes the product UUH or LHL, where U and L are upper or lower triangular matrices (unblocked algorithm).

Purpose:

``` ZLAUU2 computes the product U * U**H or L**H * L, where the triangular
factor U or L is stored in the upper or lower triangular part of
the array A.

If UPLO = 'U' or 'u' then the upper triangle of the result is stored,
overwriting the factor U in A.
If UPLO = 'L' or 'l' then the lower triangle of the result is stored,
overwriting the factor L in A.

This is the unblocked form of the algorithm, calling Level 2 BLAS.```
Parameters

UPLO

```          UPLO is CHARACTER*1
Specifies whether the triangular factor stored in the array A
is upper or lower triangular:
= 'U':  Upper triangular
= 'L':  Lower triangular```

N

```          N is INTEGER
The order of the triangular factor U or L.  N >= 0.```

A

```          A is COMPLEX*16 array, dimension (LDA,N)
On entry, the triangular factor U or L.
On exit, if UPLO = 'U', the upper triangle of A is
overwritten with the upper triangle of the product U * U**H;
if UPLO = 'L', the lower triangle of A is overwritten with
the lower triangle of the product L**H * L.```

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 = -k, the k-th argument had an illegal value```
Author

Univ. of Tennessee

Univ. of California Berkeley