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LAPACK: Linear Algebra PACKage
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zlarfgp.f File Reference

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Functions/Subroutines

subroutine zlarfgp (N, ALPHA, X, INCX, TAU)
 ZLARFGP generates an elementary reflector (Householder matrix) with non-negatibe beta. More...
 

Function/Subroutine Documentation

subroutine zlarfgp ( integer  N,
complex*16  ALPHA,
complex*16, dimension( * )  X,
integer  INCX,
complex*16  TAU 
)

ZLARFGP generates an elementary reflector (Householder matrix) with non-negatibe beta.

Download ZLARFGP + dependencies [TGZ] [ZIP] [TXT]

Purpose:
 ZLARFGP generates a complex elementary reflector H of order n, such
 that

       H**H * ( alpha ) = ( beta ),   H**H * H = I.
              (   x   )   (   0  )

 where alpha and beta are scalars, beta is real and non-negative, and
 x is an (n-1)-element complex vector.  H is represented in the form

       H = I - tau * ( 1 ) * ( 1 v**H ) ,
                     ( v )

 where tau is a complex scalar and v is a complex (n-1)-element
 vector. Note that H is not hermitian.

 If the elements of x are all zero and alpha is real, then tau = 0
 and H is taken to be the unit matrix.
Parameters
[in]N
          N is INTEGER
          The order of the elementary reflector.
[in,out]ALPHA
          ALPHA is COMPLEX*16
          On entry, the value alpha.
          On exit, it is overwritten with the value beta.
[in,out]X
          X is COMPLEX*16 array, dimension
                         (1+(N-2)*abs(INCX))
          On entry, the vector x.
          On exit, it is overwritten with the vector v.
[in]INCX
          INCX is INTEGER
          The increment between elements of X. INCX > 0.
[out]TAU
          TAU is COMPLEX*16
          The value tau.
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date
September 2012

Definition at line 105 of file zlarfgp.f.

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