# zupgtr.f (3) - Linux Man Pages

zupgtr.f -

## SYNOPSIS

### Functions/Subroutines

subroutine zupgtr (UPLO, N, AP, TAU, Q, LDQ, WORK, INFO)
ZUPGTR

## Function/Subroutine Documentation

### subroutine zupgtr (characterUPLO, integerN, complex*16, dimension( * )AP, complex*16, dimension( * )TAU, complex*16, dimension( ldq, * )Q, integerLDQ, complex*16, dimension( * )WORK, integerINFO)

ZUPGTR

Purpose:

``` ZUPGTR 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
ZHPTRD 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 ZHPTRD;
= 'L': Lower triangular packed storage used in previous
call to ZHPTRD.
```

N

```          N is INTEGER
The order of the matrix Q. N >= 0.
```

AP

```          AP is COMPLEX*16 array, dimension (N*(N+1)/2)
The vectors which define the elementary reflectors, as
returned by ZHPTRD.
```

TAU

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

Q

```          Q is COMPLEX*16 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*16 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