zungtr (l)  Linux Manuals
zungtr: generates a complex unitary matrix Q which is defined as the product of n1 elementary reflectors of order N, as returned by ZHETRD
NAME
ZUNGTR  generates a complex unitary matrix Q which is defined as the product of n1 elementary reflectors of order N, as returned by ZHETRDSYNOPSIS
 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 n1 elementary reflectors of order N, as returned by ZHETRD: if UPLO = aqUaq, Q = H(n1) . . . H(2) H(1),if UPLO = aqLaq, Q = H(1) H(2) . . . H(n1).
ARGUMENTS
 UPLO (input) CHARACTER*1
 = aqUaq: Upper triangle of A contains elementary reflectors from ZHETRD; = aqLaq: 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 NbyN unitary matrix Q.
 LDA (input) INTEGER
 The leading dimension of the array A. LDA >= N.
 TAU (input) COMPLEX*16 array, dimension (N1)
 TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by ZHETRD.
 WORK (workspace/output) COMPLEX*16 array, dimension (MAX(1,LWORK))
 On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
 LWORK (input) INTEGER
 The dimension of the array WORK. LWORK >= N1. For optimum performance LWORK >= (N1)*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 ith argument had an illegal value