zunghr(3P) Sun Performance Library zunghr(3P)NAMEzunghr - generate a complex unitary matrix Q which is defined as the
product of IHI-ILO elementary reflectors of order N, as returned by
ZGEHRD
SYNOPSIS
SUBROUTINE ZUNGHR(N, ILO, IHI, A, LDA, TAU, WORK, LWORK, INFO)
DOUBLE COMPLEX A(LDA,*), TAU(*), WORK(*)
INTEGER N, ILO, IHI, LDA, LWORK, INFO
SUBROUTINE ZUNGHR_64(N, ILO, IHI, A, LDA, TAU, WORK, LWORK, INFO)
DOUBLE COMPLEX A(LDA,*), TAU(*), WORK(*)
INTEGER*8 N, ILO, IHI, LDA, LWORK, INFO
F95 INTERFACE
SUBROUTINE UNGHR([N], ILO, IHI, A, [LDA], TAU, [WORK], [LWORK], [INFO])
COMPLEX(8), DIMENSION(:) :: TAU, WORK
COMPLEX(8), DIMENSION(:,:) :: A
INTEGER :: N, ILO, IHI, LDA, LWORK, INFO
SUBROUTINE UNGHR_64([N], ILO, IHI, A, [LDA], TAU, [WORK], [LWORK],
[INFO])
COMPLEX(8), DIMENSION(:) :: TAU, WORK
COMPLEX(8), DIMENSION(:,:) :: A
INTEGER(8) :: N, ILO, IHI, LDA, LWORK, INFO
C INTERFACE
#include <sunperf.h>
void zunghr(int n, int ilo, int ihi, doublecomplex *a, int lda, double‐
complex *tau, int *info);
void zunghr_64(long n, long ilo, long ihi, doublecomplex *a, long lda,
doublecomplex *tau, long *info);
PURPOSEzunghr generates a complex unitary matrix Q which is defined as the
product of IHI-ILO elementary reflectors of order N, as returned by
ZGEHRD:
Q = H(ilo) H(ilo+1) . . . H(ihi-1).
ARGUMENTS
N (input) The order of the matrix Q. N >= 0.
ILO (input)
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 subma‐
trix Q(ilo+1:ihi,ilo+1:ihi). 1 <= ILO <= IHI <= N, if N > 0;
ILO=1 and IHI=0, if N=0.
IHI (input)
See the description of IHI.
A (input/output)
On entry, the vectors which define the elementary reflectors,
as returned by ZGEHRD. On exit, the N-by-N unitary matrix Q.
LDA (input)
The leading dimension of the array A. LDA >= max(1,N).
TAU (input)
TAU(i) must contain the scalar factor of the elementary
reflector H(i), as returned by ZGEHRD.
WORK (workspace)
On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
LWORK (input)
The dimension of the array WORK. LWORK >= IHI-ILO. For opti‐
mum performance LWORK >= (IHI-ILO)*NB, where NB is the opti‐
mal 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)
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
6 Mar 2009 zunghr(3P)