cupgtr(3)

NAME

CUPGTR - generate a complex unitary matrix Q which is de

fined as the product of n-1 elementary reflectors H(i) of order

n, as returned by CHPTRD using packed storage

SYNOPSIS

SUBROUTINE CUPGTR( UPLO, N, AP, TAU, Q, LDQ, WORK, INFO )
    CHARACTER      UPLO
    INTEGER        INFO, LDQ, N
    COMPLEX        AP( * ), Q( LDQ, * ), TAU( * ), WORK( *
)

PURPOSE

CUPGTR generates a complex unitary matrix Q which is de

fined as the product of n-1 elementary reflectors H(i) of order

n, as returned by CHPTRD using packed storage: 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 triangular packed storage used in

previous call to CHPTRD; = 'L': Lower triangular packed storage

used in previous call to CHPTRD.

N (input) INTEGER

The order of the matrix Q. N >= 0.

AP (input) COMPLEX array, dimension (N*(N+1)/2)

The vectors which define the elementary reflec

tors, as returned by CHPTRD.

TAU (input) COMPLEX array, dimension (N-1)

TAU(i) must contain the scalar factor of the ele

mentary reflector H(i), as returned by CHPTRD.

Q (output) COMPLEX array, dimension (LDQ,N)

The N-by-N unitary matrix Q.

LDQ (input) INTEGER

The leading dimension of the array Q. LDQ >=

max(1,N).

WORK (workspace) COMPLEX array, dimension (N-1)

INFO (output) INTEGER

= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille

gal value

LAPACK version 3.0 15 June 2000

CUPGTR(3)