# zunbdb5 (3) - Linux Manuals

zunbdb5.f -

## SYNOPSIS

### Functions/Subroutines

subroutine zunbdb5 (M1, M2, N, X1, INCX1, X2, INCX2, Q1, LDQ1, Q2, LDQ2, WORK, LWORK, INFO)
ZUNBDB5

## Function/Subroutine Documentation

### subroutine zunbdb5 (integerM1, integerM2, integerN, complex*16, dimension(*)X1, integerINCX1, complex*16, dimension(*)X2, integerINCX2, complex*16, dimension(ldq1,*)Q1, integerLDQ1, complex*16, dimension(ldq2,*)Q2, integerLDQ2, complex*16, dimension(*)WORK, integerLWORK, integerINFO)

ZUNBDB5 .SH "Purpose:"

``` ZUNBDB5 orthogonalizes the column vector
X = [ X1 ]
[ X2 ]
with respect to the columns of
Q = [ Q1 ] .
[ Q2 ]
The columns of Q must be orthonormal.

If the projection is zero according to Kahan's "twice is enough"
criterion, then some other vector from the orthogonal complement
is returned. This vector is chosen in an arbitrary but deterministic
way..fi

Parameters:
M1

M1 is INTEGER
The dimension of X1 and the number of rows in Q1. 0 <= M1.
```

M2

```          M2 is INTEGER
The dimension of X2 and the number of rows in Q2. 0 <= M2.
```

N

```          N is INTEGER
The number of columns in Q1 and Q2. 0 <= N.
```

X1

```          X1 is COMPLEX*16 array, dimension (M1)
On entry, the top part of the vector to be orthogonalized.
On exit, the top part of the projected vector.
```

INCX1

```          INCX1 is INTEGER
Increment for entries of X1.
```

X2

```          X2 is COMPLEX*16 array, dimension (M2)
On entry, the bottom part of the vector to be
orthogonalized. On exit, the bottom part of the projected
vector.
```

INCX2

```          INCX2 is INTEGER
Increment for entries of X2.
```

Q1

```          Q1 is COMPLEX*16 array, dimension (LDQ1, N)
The top part of the orthonormal basis matrix.
```

LDQ1

```          LDQ1 is INTEGER
The leading dimension of Q1. LDQ1 >= M1.
```

Q2

```          Q2 is COMPLEX*16 array, dimension (LDQ2, N)
The bottom part of the orthonormal basis matrix.
```

LDQ2

```          LDQ2 is INTEGER
The leading dimension of Q2. LDQ2 >= M2.
```

WORK

```          WORK is COMPLEX*16 array, dimension (LWORK)
```

LWORK

```          LWORK is INTEGER
The dimension of the array WORK. LWORK >= N.
```

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