# cupgtr.f

## NAME

cupgtr.f −

## SYNOPSIS

**Functions/Subroutines**

subroutine **cupgtr** (UPLO, N, AP, TAU, Q, LDQ, WORK, INFO)

CUPGTR

## Function/Subroutine Documentation

**subroutine cupgtr (characterUPLO, integerN, complex, dimension( * )AP, complex, dimension( * )TAU, complex, dimension( ldq, * )Q, integerLDQ, complex, dimension( * )WORK, integerINFO)**

CUPGTR

**Purpose:**

CUPGTR generates a complex unitary matrix Q which is defined 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).

**Parameters:**

*UPLO*

UPLO is 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*

N is INTEGER

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

*AP*

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

The vectors which define the elementary reflectors, as

returned by CHPTRD.

*TAU*

TAU is COMPLEX array, dimension (N-1)

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

reflector H(i), as returned by CHPTRD.

*Q*

Q is COMPLEX array, dimension (LDQ,N)

The N-by-N unitary matrix Q.

*LDQ*

LDQ is INTEGER

The leading dimension of the array Q. LDQ >= max(1,N).

*WORK*

WORK is COMPLEX array, dimension (N-1)

*INFO*

INFO is INTEGER

= 0: successful exit

< 0: if INFO = -i, the i-th argument had an illegal value

**Author:**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**

November 2011

Definition at line 115 of file cupgtr.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.