---
name: "cung2l"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/cung2l/3lapack"
---

# cung2l(3lapack)

generates an m by n complex matrix Q with orthonormal columns,

## NAME

CUNG2L - generates an m by n complex matrix Q with orthonormal columns,

## SYNOPSIS

- SUBROUTINE CUNG2L(

  M, N, K, A, LDA, TAU, WORK, INFO )

- INTEGER

  INFO, K, LDA, M, N

- COMPLEX

  A( LDA, \* ), TAU( \* ), WORK( \* )

## PURPOSE

CUNG2L generates an m by n complex matrix Q with orthonormal columns, which is defined as the last n columns of a product of k elementary reflectors of order m\
\
       Q  =  H(k) . . . H(2) H(1)\
 as returned by CGEQLF.\

## ARGUMENTS

- M (input) INTEGER

  The number of rows of the matrix Q. M \>= 0.

- N (input) INTEGER

  The number of columns of the matrix Q. M \>= N \>= 0.

- K (input) INTEGER

  The number of elementary reflectors whose product defines the matrix Q. N \>= K \>= 0.

- A (input/output) COMPLEX array, dimension (LDA,N)

  On entry, the (n-k+i)-th column must contain the vector which defines the elementary reflector H(i), for i = 1,2,...,k, as returned by CGEQLF in the last k columns of its array argument A. On exit, the m-by-n matrix Q.

- LDA (input) INTEGER

  The first dimension of the array A. LDA \>= max(1,M).

- TAU (input) COMPLEX array, dimension (K)

  TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by CGEQLF.

- WORK (workspace) COMPLEX array, dimension (N)

  - INFO (output) INTEGER

  \= 0: successful exit\
   \< 0: if INFO = -i, the i-th argument has an illegal value