zunghr (l)  Linux Man Pages
zunghr: generates a complex unitary matrix Q which is defined as the product of IHIILO elementary reflectors of order N, as returned by ZGEHRD
Command to display zunghr
manual in Linux: $ man l zunghr
NAME
ZUNGHR  generates a complex unitary matrix Q which is defined as the product of IHIILO elementary reflectors of order N, as returned by ZGEHRD
SYNOPSIS
 SUBROUTINE ZUNGHR(

N, ILO, IHI, A, LDA, TAU, WORK, LWORK, INFO )

INTEGER
IHI, ILO, INFO, LDA, LWORK, N

COMPLEX*16
A( LDA, * ), TAU( * ), WORK( * )
PURPOSE
ZUNGHR generates a complex unitary matrix Q which is defined as the
product of IHIILO elementary reflectors of order N, as returned by
ZGEHRD:
Q = H(ilo) H(ilo+1) . . . H(ihi1).
ARGUMENTS
 N (input) INTEGER

The order of the matrix Q. N >= 0.
 ILO (input) INTEGER

IHI (input) INTEGER
ILO and IHI must have the same values as in the previous call
of ZGEHRD. Q is equal to the unit matrix except in the
submatrix Q(ilo+1:ihi,ilo+1:ihi).
1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.
 A (input/output) COMPLEX*16 array, dimension (LDA,N)

On entry, the vectors which define the elementary reflectors,
as returned by ZGEHRD.
On exit, the NbyN unitary matrix Q.
 LDA (input) INTEGER

The leading dimension of the array A. LDA >= max(1,N).
 TAU (input) COMPLEX*16 array, dimension (N1)

TAU(i) must contain the scalar factor of the elementary
reflector H(i), as returned by ZGEHRD.
 WORK (workspace/output) COMPLEX*16 array, dimension (MAX(1,LWORK))

On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
 LWORK (input) INTEGER

The dimension of the array WORK. LWORK >= IHIILO.
For optimum performance LWORK >= (IHIILO)*NB, where NB is
the optimal blocksize.
If LWORK = 1, then a workspace query is assumed; the routine
only calculates the optimal size of the WORK array, returns
this value as the first entry of the WORK array, and no error
message related to LWORK is issued by XERBLA.
 INFO (output) INTEGER

= 0: successful exit
< 0: if INFO = i, the ith argument had an illegal value
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