cunghr-f(3)

cunghr.f –

Synopsis

Functions/Subroutines

subroutine cunghr (N, ILO, IHI, A, LDA, TAU, WORK, LWORK, INFO)
CUNGHR

Function/Subroutine Documentation

subroutine cunghr (integerN, integerILO, integerIHI, complex, dimension( lda, * )A, integerLDA, complex, dimension( * )TAU, complex, dimension( * )WORK, integerLWORK, integerINFO)

CUNGHR

Purpose:

 CUNGHR generates a complex unitary matrix Q which is defined as the
 product of IHI-ILO elementary reflectors of order N, as returned by
 CGEHRD:
 Q = H(ilo) H(ilo+1) . . . H(ihi-1).

Parameters:

 N is INTEGER
 The order of the matrix Q. N >= 0.

ILO

 ILO is INTEGER

IHI

 IHI is 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 is COMPLEX array, dimension (LDA,N)
 On entry, the vectors which define the elementary reflectors,
 as returned by CGEHRD.
 On exit, the N-by-N unitary matrix Q.

LDA

 LDA is INTEGER
 The leading dimension of the array A. LDA >= max(1,N).

TAU

 TAU is COMPLEX array, dimension (N-1)
 TAU(i) must contain the scalar factor of the elementary
 reflector H(i), as returned by CGEHRD.

WORK

 WORK is COMPLEX array, dimension (MAX(1,LWORK))
 On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

LWORK

 LWORK is INTEGER
 The dimension of the array WORK. LWORK >= IHI-ILO.
 For optimum performance LWORK >= (IHI-ILO)*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

 INFO is INTEGER
 = 0: successful exit
 < 0: if INFO = -i, the i-th argument had an illegal value

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

November 2011

Definition at line 127 of file cunghr.f.

Author

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