double_eig(3) LAPACK double_eig(3)

double_eig

# SYNOPSIS¶

## Functions¶

subroutine dlarfy (UPLO, N, V, INCV, TAU, C, LDC, WORK)
DLARFY

# Detailed Description¶

This is the group of double LAPACK TESTING EIG routines.

# Function Documentation¶

## subroutine dlarfy (character UPLO, integer N, double precision, dimension( * ) V, integer INCV, double precision TAU, double precision, dimension( ldc, * ) C, integer LDC, double precision, dimension( * ) WORK)¶

DLARFY

Purpose:

``` DLARFY applies an elementary reflector, or Householder matrix, H,
to an n x n symmetric 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
symmetric 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 DOUBLE PRECISION 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 DOUBLE PRECISION
The value tau as described above.
```

C

```          C is DOUBLE PRECISION 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 DOUBLE PRECISION array, dimension (N)
```

Author:

Univ. of Tennessee

Univ. of California Berkeley