cunghr

NAME

cunghr - generate a complex unitary matrix Q which is defined as the product of IHI-ILO elementary reflectors of order N, as returned by CGEHRD

SYNOPSIS 

  SUBROUTINE CUNGHR( N, ILO, IHI, A, LDA, TAU, WORK, LWORK, INFO)
  COMPLEX A(LDA,*), TAU(*), WORK(*)
  INTEGER N, ILO, IHI, LDA, LWORK, INFO
 
  SUBROUTINE CUNGHR_64( N, ILO, IHI, A, LDA, TAU, WORK, LWORK, INFO)
  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, DIMENSION(:) :: TAU, WORK
  COMPLEX, DIMENSION(:,:) :: A
  INTEGER :: N, ILO, IHI, LDA, LWORK, INFO
 
  SUBROUTINE UNGHR_64( [N], ILO, IHI, A, [LDA], TAU, [WORK], [LWORK], 
 *       [INFO])
  COMPLEX, DIMENSION(:) :: TAU, WORK
  COMPLEX, DIMENSION(:,:) :: A
  INTEGER(8) :: N, ILO, IHI, LDA, LWORK, INFO

C INTERFACE

#include <sunperf.h>

void cunghr(int n, int ilo, int ihi, complex *a, int lda, complex *tau, int *info);

void cunghr_64(long n, long ilo, long ihi, complex *a, long lda, complex *tau, long *info);

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).

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 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.

* IHI (input)
See the description of IHI.

* A (input/output)
On entry, the vectors which define the elementary reflectors, as returned by CGEHRD. 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 CGEHRD.

* 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 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 (output)