---
name: "dorgqr.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/dorgqr.f"
---

# dorgqr.f(3)

## NAME

SRC/dorgqr.f

## SYNOPSIS

### Functions/Subroutines

subroutine **dorgqr** (m, n, k, a, lda, tau, work, lwork, info)\
 **DORGQR**

## Function/Subroutine Documentation

### subroutine dorgqr (integer m, integer n, integer k, double precision, dimension( lda, \* ) a, integer lda, double precision, dimension( \* ) tau, double precision, dimension( \* ) work, integer lwork, integer info)

**DORGQR**

**Purpose:**

```
!>
!> DORGQR generates an M-by-N real matrix Q with orthonormal columns,
!> which is defined as the first N columns of a product of K elementary
!> reflectors of order M
!>
!>       Q  =  H(1) H(2) . . . H(k)
!>
!> as returned by DGEQRF.
!>
```

**Parameters**

*M*

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

*N*

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

*K*

```
!>          K is INTEGER
!>          The number of elementary reflectors whose product defines the
!>          matrix Q. N >= K >= 0.
!>
```

*A*

```
!>          A is DOUBLE PRECISION array, dimension (LDA,N)
!>          On entry, the i-th column must contain the vector which
!>          defines the elementary reflector H(i), for i = 1,2,...,k, as
!>          returned by DGEQRF in the first k columns of its array
!>          argument A.
!>          On exit, the M-by-N matrix Q.
!>
```

*LDA*

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

*TAU*

```
!>          TAU is DOUBLE PRECISION array, dimension (K)
!>          TAU(i) must contain the scalar factor of the elementary
!>          reflector H(i), as returned by DGEQRF.
!>
```

*WORK*

```
!>          WORK is DOUBLE PRECISION 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. LWORK >= max(1,N).
!>          For optimum performance LWORK >= N*NB, where NB is the
!>          optimal blocksize.
!>
!>          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 has an illegal value
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **127** of file **dorgqr.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.