SRC/zung2l.f(3)

💅 SRC/zung2l.f(3) — Library Functions Manual 💅

okay bestie, welcome to the SRC/zung2l.f(3) page from the Library Functions Manual — manual name successfully folded in near the top, we move cute here. This one is all about zung2l, an LAPACK unblocked girlie that builds Q from a QL factorization. 🦋

🌸 NAME

SRC/zung2l.f

✨ SYNOPSIS

🎀 Functions/Subroutines

• subroutine zung2l (m, n, k, a, lda, tau, work, info) — ZUNG2L generates all or part of the unitary matrix Q from a QL factorization determined by cgeqlf (unblocked algorithm).

🫶 Function/Subroutine Documentation

💅 subroutine zung2l

subroutine zung2l (integer m, integer n, integer k, complex*16, dimension(
     lda, * ) a, integer lda, complex*16, dimension( * ) tau, complex*16,
     dimension( * ) work, integer info)

ZUNG2L generates all or part of the unitary matrix Q from a QL factorization determined by cgeqlf (unblocked algorithm).

🌟 Purpose

ZUNG2L 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 ZGEQLF.

🍓 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*16 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 ZGEQLF 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*16 array, dimension (K); TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by ZGEQLF.
• WORK — WORK is COMPLEX*16 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 zung2l.f.

Definition at line 113 of file zung2l.f.

🧚 Author

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