---
name: "clasyf_aa.f"
section: "3"
platform: "linux"
package: "lapack-doc"
version: "3.12.1-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/clasyf_aa.f"
---

# clasyf\_aa.f(3)

## NAME

SRC/clasyf\_aa.f

## SYNOPSIS

### Functions/Subroutines

subroutine **clasyf\_aa** (uplo, j1, m, nb, a, lda, ipiv, h, ldh, work)\
 **CLASYF\_AA**

## Function/Subroutine Documentation

### subroutine clasyf\_aa (character uplo, integer j1, integer m, integer nb, complex, dimension( lda, \* ) a, integer lda, integer, dimension( \* ) ipiv, complex, dimension( ldh, \* ) h, integer ldh, complex, dimension( \* ) work)

**CLASYF\_AA**

**Purpose:**

```
!>
!> DLATRF_AA factorizes a panel of a complex symmetric matrix A using
!> the Aasen's algorithm. The panel consists of a set of NB rows of A
!> when UPLO is U, or a set of NB columns when UPLO is L.
!>
!> In order to factorize the panel, the Aasen's algorithm requires the
!> last row, or column, of the previous panel. The first row, or column,
!> of A is set to be the first row, or column, of an identity matrix,
!> which is used to factorize the first panel.
!>
!> The resulting J-th row of U, or J-th column of L, is stored in the
!> (J-1)-th row, or column, of A (without the unit diagonals), while
!> the diagonal and subdiagonal of A are overwritten by those of T.
!>
!>
```

**Parameters**

*UPLO*

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

*J1*

```
!>          J1 is INTEGER
!>          The location of the first row, or column, of the panel
!>          within the submatrix of A, passed to this routine, e.g.,
!>          when called by CSYTRF_AA, for the first panel, J1 is 1,
!>          while for the remaining panels, J1 is 2.
!>
```

*M*

```
!>          M is INTEGER
!>          The dimension of the submatrix. M >= 0.
!>
```

*NB*

```
!>          NB is INTEGER
!>          The dimension of the panel to be facotorized.
!>
```

*A*

```
!>          A is COMPLEX array, dimension (LDA,M) for
!>          the first panel, while dimension (LDA,M+1) for the
!>          remaining panels.
!>
!>          On entry, A contains the last row, or column, of
!>          the previous panel, and the trailing submatrix of A
!>          to be factorized, except for the first panel, only
!>          the panel is passed.
!>
!>          On exit, the leading panel is factorized.
!>
```

*LDA*

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

*IPIV*

```
!>          IPIV is INTEGER array, dimension (M)
!>          Details of the row and column interchanges,
!>          the row and column k were interchanged with the row and
!>          column IPIV(k).
!>
```

*H*

```
!>          H is COMPLEX workspace, dimension (LDH,NB).
!>
!>
```

*LDH*

```
!>          LDH is INTEGER
!>          The leading dimension of the workspace H. LDH >= max(1,M).
!>
```

*WORK*

```
!>          WORK is COMPLEX workspace, dimension (M).
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **142** of file **clasyf\_aa.f**.

## Author

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