CUNG2L(3)

📦 version 3.12.0, in opensuse-leap 16.0

💖 NAME 💖

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/cung2l.f

okay bestie, you're in the Library Functions Manual, and the header energy is literally /home/abui...RC/cung2l.f(3) Library Functions Manual/home/abui...RC/cung2l.f(3). The main character here is CUNG2L, and it is so good at one specific thing: generating all or part of the unitary matrix Q from a QL factorization determined by cgeqlf (unblocked algorithm). ✨

🌸 SYNOPSIS 🌸

Functions/Subroutines

subroutine CUNG2L (m, n, k, a, lda, tau, work, info)
    CUNG2L generates all or part of the unitary matrix Q from a QL
    factorization determined by cgeqlf (unblocked algorithm).

🛠️ Function/Subroutine Documentation 🛠️

subroutine CUNG2L (integer m, integer n, integer k, complex, dimension( lda,
* ) a, integer lda, complex, dimension( * ) tau, complex, dimension( * )
work, integer info)

CUNG2L generates all or part of the unitary matrix Q from a QL factorization determined by cgeqlf (unblocked algorithm).

🎯 Purpose

okay so here's the purpose, bestie: CUNG2L generates an m by n complex matrix Q with orthonormal columns, and Q is defined as the last n columns of a product of k elementary reflectors of order m:

Q  =  H(k) . . . H(2) H(1)

...exactly as returned by CGEQLF. 👑

🧸 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 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

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 CGEQLF.

WORK

WORK is COMPLEX array, dimension (N).

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 113 of file cung2l.f.

👑 Author 👑

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