---
name: "cunm22.f"
section: "3"
platform: "linux"
package: "lapack-doc"
version: "3.12.1-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/cunm22.f"
---

# cunm22.f(3)

## NAME

SRC/cunm22.f

## SYNOPSIS

### Functions/Subroutines

subroutine **cunm22** (side, trans, m, n, n1, n2, q, ldq, c, ldc, work, lwork, info)\
 **CUNM22** multiplies a general matrix by a banded unitary matrix.

## Function/Subroutine Documentation

### subroutine cunm22 (character side, character trans, integer m, integer n, integer n1, integer n2, complex, dimension( ldq, \* ) q, integer ldq, complex, dimension( ldc, \* ) c, integer ldc, complex, dimension( \* ) work, integer lwork, integer info)

**CUNM22** multiplies a general matrix by a banded unitary matrix.

**Purpose**

```
!>
!>  CUNM22 overwrites the general complex M-by-N matrix C with
!>
!>                  SIDE = 'L'     SIDE = 'R'
!>  TRANS = 'N':      Q * C          C * Q
!>  TRANS = 'C':      Q**H * C       C * Q**H
!>
!>  where Q is a complex unitary matrix of order NQ, with NQ = M if
!>  SIDE = 'L' and NQ = N if SIDE = 'R'.
!>  The unitary matrix Q processes a 2-by-2 block structure
!>
!>         [  Q11  Q12  ]
!>     Q = [            ]
!>         [  Q21  Q22  ],
!>
!>  where Q12 is an N1-by-N1 lower triangular matrix and Q21 is an
!>  N2-by-N2 upper triangular matrix.
!>
```

**Parameters**

*SIDE*

```
!>          SIDE is CHARACTER*1
!>          = 'L': apply Q or Q**H from the Left;
!>          = 'R': apply Q or Q**H from the Right.
!>
```

*TRANS*

```
!>          TRANS is CHARACTER*1
!>          = 'N':  apply Q (No transpose);
!>          = 'C':  apply Q**H (Conjugate transpose).
!>
```

*M*

```
!>          M is INTEGER
!>          The number of rows of the matrix C. M >= 0.
!>
```

*N*

```
!>          N is INTEGER
!>          The number of columns of the matrix C. N >= 0.
!>
```

*N1* \
 *N2*

```
!>          N1 is INTEGER
!>          N2 is INTEGER
!>          The dimension of Q12 and Q21, respectively. N1, N2 >= 0.
!>          The following requirement must be satisfied:
!>          N1 + N2 = M if SIDE = 'L' and N1 + N2 = N if SIDE = 'R'.
!>
```

*Q*

```
!>          Q is COMPLEX array, dimension
!>                              (LDQ,M) if SIDE = 'L'
!>                              (LDQ,N) if SIDE = 'R'
!>
```

*LDQ*

```
!>          LDQ is INTEGER
!>          The leading dimension of the array Q.
!>          LDQ >= max(1,M) if SIDE = 'L'; LDQ >= max(1,N) if SIDE = 'R'.
!>
```

*C*

```
!>          C is COMPLEX array, dimension (LDC,N)
!>          On entry, the M-by-N matrix C.
!>          On exit, C is overwritten by Q*C or Q**H*C or C*Q**H or C*Q.
!>
```

*LDC*

```
!>          LDC is INTEGER
!>          The leading dimension of the array C. LDC >= max(1,M).
!>
```

*WORK*

```
!>          WORK is COMPLEX array, dimension (MAX(1,LWORK))
!>          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
!>
```

*LWORK*

```
!>          LWORK is INTEGER
!>          The dimension of the array WORK.
!>          If SIDE = 'L', LWORK >= max(1,N);
!>          if SIDE = 'R', LWORK >= max(1,M).
!>          For optimum performance LWORK >= M*N.
!>
!>          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*

```
!>          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.

Definition at line **160** of file **cunm22.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.