---
name: "unglq"
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/unglq"
---

# unglq(3)

{un,or}glq: generate explicit Q from gelqf

## NAME

unglq - {un,or}glq: generate explicit Q from gelqf

## SYNOPSIS

### Functions

subroutine **cunglq** (m, n, k, a, lda, tau, work, lwork, info)\
 **CUNGLQ**  subroutine **dorglq** (m, n, k, a, lda, tau, work, lwork, info)\
 **DORGLQ**  subroutine **sorglq** (m, n, k, a, lda, tau, work, lwork, info)\
 **SORGLQ**  subroutine **zunglq** (m, n, k, a, lda, tau, work, lwork, info)\
 **ZUNGLQ**

## Detailed Description

## Function Documentation

### subroutine cunglq (integer m, integer n, integer k, complex, dimension( lda, \* ) a, integer lda, complex, dimension( \* ) tau, complex, dimension( \* ) work, integer lwork, integer info)

**CUNGLQ**

**Purpose:**

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

**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. N >= M.
!>
```

*K*

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

*A*

```
!>          A is COMPLEX array, dimension (LDA,N)
!>          On entry, the i-th row must contain the vector which defines
!>          the elementary reflector H(i), for i = 1,2,...,k, as returned
!>          by CGELQF in the first k rows 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 COMPLEX array, dimension (K)
!>          TAU(i) must contain the scalar factor of the elementary
!>          reflector H(i), as returned by CGELQF.
!>
```

*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. LWORK >= max(1,M).
!>          For optimum performance LWORK >= M*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 **126** of file **cunglq.f**.

### subroutine dorglq (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)

**DORGLQ**

**Purpose:**

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

**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. N >= M.
!>
```

*K*

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

*A*

```
!>          A is DOUBLE PRECISION array, dimension (LDA,N)
!>          On entry, the i-th row must contain the vector which defines
!>          the elementary reflector H(i), for i = 1,2,...,k, as returned
!>          by DGELQF in the first k rows 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 DGELQF.
!>
```

*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,M).
!>          For optimum performance LWORK >= M*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 **126** of file **dorglq.f**.

### subroutine sorglq (integer m, integer n, integer k, real, dimension( lda, \* ) a, integer lda, real, dimension( \* ) tau, real, dimension( \* ) work, integer lwork, integer info)

**SORGLQ**

**Purpose:**

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

**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. N >= M.
!>
```

*K*

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

*A*

```
!>          A is REAL array, dimension (LDA,N)
!>          On entry, the i-th row must contain the vector which defines
!>          the elementary reflector H(i), for i = 1,2,...,k, as returned
!>          by SGELQF in the first k rows 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 REAL array, dimension (K)
!>          TAU(i) must contain the scalar factor of the elementary
!>          reflector H(i), as returned by SGELQF.
!>
```

*WORK*

```
!>          WORK is REAL 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,M).
!>          For optimum performance LWORK >= M*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 **126** of file **sorglq.f**.

### subroutine zunglq (integer m, integer n, integer k, complex\*16, dimension( lda, \* ) a, integer lda, complex\*16, dimension( \* ) tau, complex\*16, dimension( \* ) work, integer lwork, integer info)

**ZUNGLQ**

**Purpose:**

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

**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. N >= M.
!>
```

*K*

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

*A*

```
!>          A is COMPLEX*16 array, dimension (LDA,N)
!>          On entry, the i-th row must contain the vector which defines
!>          the elementary reflector H(i), for i = 1,2,...,k, as returned
!>          by ZGELQF in the first k rows 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 COMPLEX*16 array, dimension (K)
!>          TAU(i) must contain the scalar factor of the elementary
!>          reflector H(i), as returned by ZGELQF.
!>
```

*WORK*

```
!>          WORK is COMPLEX*16 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,M).
!>          For optimum performance LWORK >= M*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 **126** of file **zunglq.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.