dorghr(3P) Sun Performance Library dorghr(3P)NAMEdorghr - generate a real orthogonal matrix Q which is defined as the
product of IHI-ILO elementary reflectors of order N, as returned by
DGEHRD
SYNOPSIS
SUBROUTINE DORGHR(N, ILO, IHI, A, LDA, TAU, WORK, LWORK, INFO)
INTEGER N, ILO, IHI, LDA, LWORK, INFO
DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*)
SUBROUTINE DORGHR_64(N, ILO, IHI, A, LDA, TAU, WORK, LWORK, INFO)
INTEGER*8 N, ILO, IHI, LDA, LWORK, INFO
DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*)
F95 INTERFACE
SUBROUTINE ORGHR([N], ILO, IHI, A, [LDA], TAU, [WORK], [LWORK], [INFO])
INTEGER :: N, ILO, IHI, LDA, LWORK, INFO
REAL(8), DIMENSION(:) :: TAU, WORK
REAL(8), DIMENSION(:,:) :: A
SUBROUTINE ORGHR_64([N], ILO, IHI, A, [LDA], TAU, [WORK], [LWORK],
[INFO])
INTEGER(8) :: N, ILO, IHI, LDA, LWORK, INFO
REAL(8), DIMENSION(:) :: TAU, WORK
REAL(8), DIMENSION(:,:) :: A
C INTERFACE
#include <sunperf.h>
void dorghr(int n, int ilo, int ihi, double *a, int lda, double *tau,
int *info);
void dorghr_64(long n, long ilo, long ihi, double *a, long lda, double
*tau, long *info);
PURPOSEdorghr generates a real orthogonal matrix Q which is defined as the
product of IHI-ILO elementary reflectors of order N, as returned by
DGEHRD:
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 DGEHRD. 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 ILO.
A (input/output)
On entry, the vectors which define the elementary reflectors,
as returned by DGEHRD. On exit, the N-by-N orthogonal 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 DGEHRD.
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 dorghr(3P)
