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

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

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

COMPLEX
A( LDA, * ), TAU( * ), WORK( * )
PURPOSE
CUNGHR generates a complex unitary matrix Q which is defined as the
product of IHIILO elementary reflectors of order N, as returned by
CGEHRD:
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 CGEHRD. 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 array, dimension (LDA,N)

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

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

TAU(i) must contain the scalar factor of the elementary
reflector H(i), as returned by CGEHRD.
 WORK (workspace/output) COMPLEX 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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