## table of contents

double_eig(3) | LAPACK | double_eig(3) |

# NAME¶

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

Univ. of Colorado Denver

NAG Ltd.

**Date:**

December 2016

# Author¶

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