---
name: "cgeqrt2.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/cgeqrt2.f"
---

# cgeqrt2.f(3)

## NAME

SRC/cgeqrt2.f

## SYNOPSIS

### Functions/Subroutines

subroutine **cgeqrt2** (m, n, a, lda, t, ldt, info)\
 **CGEQRT2** computes a QR factorization of a general real or complex matrix using the compact WY representation of Q.

## Function/Subroutine Documentation

### subroutine cgeqrt2 (integer m, integer n, complex, dimension( lda, \* ) a, integer lda, complex, dimension( ldt, \* ) t, integer ldt, integer info)

**CGEQRT2** computes a QR factorization of a general real or complex matrix using the compact WY representation of Q.

**Purpose:**

```
!>
!> CGEQRT2 computes a QR factorization of a complex M-by-N matrix A,
!> using the compact WY representation of Q.
!>
```

**Parameters**

*M*

```
!>          M is INTEGER
!>          The number of rows of the matrix A.  M >= N.
!>
```

*N*

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

*A*

```
!>          A is COMPLEX array, dimension (LDA,N)
!>          On entry, the complex M-by-N matrix A.  On exit, the elements on and
!>          above the diagonal contain the N-by-N upper triangular matrix R; the
!>          elements below the diagonal are the columns of V.  See below for
!>          further details.
!>
```

*LDA*

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

*T*

```
!>          T is COMPLEX array, dimension (LDT,N)
!>          The N-by-N upper triangular factor of the block reflector.
!>          The elements on and above the diagonal contain the block
!>          reflector T; the elements below the diagonal are not used.
!>          See below for further details.
!>
```

*LDT*

```
!>          LDT is INTEGER
!>          The leading dimension of the array T.  LDT >= max(1,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

Univ. of Colorado Denver

NAG Ltd.

**Further Details:**

```
!>
!>  The matrix V stores the elementary reflectors H(i) in the i-th column
!>  below the diagonal. For example, if M=5 and N=3, the matrix V is
!>
!>               V = (  1       )
!>                   ( v1  1    )
!>                   ( v1 v2  1 )
!>                   ( v1 v2 v3 )
!>                   ( v1 v2 v3 )
!>
!>  where the vi's represent the vectors which define H(i), which are returned
!>  in the matrix A.  The 1's along the diagonal of V are not stored in A.  The
!>  block reflector H is then given by
!>
!>               H = I - V * T * V**H
!>
!>  where V**H is the conjugate transpose of V.
!>
```

Definition at line **126** of file **cgeqrt2.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.