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RedHat 9 (Linux i386) - man page for zungtr (redhat section l)

ZUNGTR(l)					)					ZUNGTR(l)

NAME
       ZUNGTR  -  generate a complex unitary matrix Q which is defined as the product of n-1 ele-
       mentary reflectors of order N, as returned by ZHETRD

SYNOPSIS
       SUBROUTINE ZUNGTR( UPLO, N, A, LDA, TAU, WORK, LWORK, INFO )

	   CHARACTER	  UPLO

	   INTEGER	  INFO, LDA, LWORK, N

	   COMPLEX*16	  A( LDA, * ), TAU( * ), WORK( * )

PURPOSE
       ZUNGTR generates a complex unitary matrix Q which is defined as the product of n-1 elemen-
       tary  reflectors  of  order N, as returned by ZHETRD: if UPLO = 'U', Q = H(n-1) . . . H(2)
       H(1),

       if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).

ARGUMENTS
       UPLO    (input) CHARACTER*1
	       = 'U': Upper triangle of A contains elementary  reflectors  from  ZHETRD;  =  'L':
	       Lower triangle of A contains elementary reflectors from ZHETRD.

       N       (input) INTEGER
	       The order of the matrix Q. N >= 0.

       A       (input/output) COMPLEX*16 array, dimension (LDA,N)
	       On  entry,  the	vectors  which	define	the elementary reflectors, as returned by
	       ZHETRD.	On exit, the N-by-N unitary matrix Q.

       LDA     (input) INTEGER
	       The leading dimension of the array A. LDA >= N.

       TAU     (input) COMPLEX*16 array, dimension (N-1)
	       TAU(i) must contain the	scalar	factor	of  the  elementary  reflector	H(i),  as
	       returned by ZHETRD.

       WORK    (workspace/output) COMPLEX*16 array, dimension (LWORK)
	       On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

       LWORK   (input) INTEGER
	       The  dimension  of the array WORK. LWORK >= N-1.  For optimum performance LWORK >=
	       (N-1)*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 i-th argument had an illegal value

LAPACK version 3.0			   15 June 2000 				ZUNGTR(l)


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