# zungrq.f man page

zungrq.f

## Synopsis

### Functions/Subroutines

subroutine **zungrq** (M, **N**, K, A, **LDA**, TAU, WORK, LWORK, INFO)**ZUNGRQ**

## Function/Subroutine Documentation

### subroutine zungrq (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)

**ZUNGRQ**

**Purpose:**

ZUNGRQ generates an M-by-N complex matrix Q with orthonormal rows, which is defined as the last M rows of a product of K elementary reflectors of order N Q = H(1)**H H(2)**H . . . H(k)**H as returned by ZGERQF.

**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 (m-k+i)-th row must contain the vector which defines the elementary reflector H(i), for i = 1,2,...,k, as returned by ZGERQF in the last 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 ZGERQF.

*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.

**Date:**December 2016

Definition at line 130 of file zungrq.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page zungrq(3) is an alias of zungrq.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK