---
name: "clarfy.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/clarfy.f"
---

# clarfy.f(3)

## NAME

TESTING/EIG/clarfy.f

## SYNOPSIS

### Functions/Subroutines

subroutine **clarfy** (uplo, n, v, incv, tau, c, ldc, work)\
 **CLARFY**

## Function/Subroutine Documentation

### subroutine clarfy (character uplo, integer n, complex, dimension( \* ) v, integer incv, complex tau, complex, dimension( ldc, \* ) c, integer ldc, complex, dimension( \* ) work)

**CLARFY**

**Purpose:**

```
!>
!> CLARFY applies an elementary reflector, or Householder matrix, H,
!> to an n x n Hermitian matrix C, from both the left and the right.
!>
!> H is represented in the form
!>
!>    H = I - tau * v * v'
!>
!> where  tau  is a scalar and  v  is a vector.
!>
!> If  tau  is  zero, then  H  is taken to be the unit matrix.
!>
```

**Parameters**

*UPLO*

```
!>          UPLO is CHARACTER*1
!>          Specifies whether the upper or lower triangular part of the
!>          Hermitian matrix C is stored.
!>          = 'U':  Upper triangle
!>          = 'L':  Lower triangle
!>
```

*N*

```
!>          N is INTEGER
!>          The number of rows and columns of the matrix C.  N >= 0.
!>
```

*V*

```
!>          V is COMPLEX array, dimension
!>                  (1 + (N-1)*abs(INCV))
!>          The vector v as described above.
!>
```

*INCV*

```
!>          INCV is INTEGER
!>          The increment between successive elements of v.  INCV must
!>          not be zero.
!>
```

*TAU*

```
!>          TAU is COMPLEX
!>          The value tau as described above.
!>
```

*C*

```
!>          C is COMPLEX array, dimension (LDC, N)
!>          On entry, the matrix C.
!>          On exit, C is overwritten by H * C * H'.
!>
```

*LDC*

```
!>          LDC is INTEGER
!>          The leading dimension of the array C.  LDC >= max( 1, N ).
!>
```

*WORK*

```
!>          WORK is COMPLEX array, dimension (N)
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **107** of file **clarfy.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.