SRC/zunm2l.f(3)

🌸 SRC/zunm2l.f 🌸

okay bestie, welcome to the SRC/zunm2l.f page from the Library Functions Manual 💖 this is the LAPACK lore for zunm2l, and yes it is lowkey iconic.

💖 NAME 💖

SRC/zunm2l.f

✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

one very specific subroutine, coming right up:

   subroutine zunm2l (side, trans, m, n, k, a, lda, tau, c, ldc, work,
       info)

ZUNM2L multiplies a general matrix by the unitary matrix from a QL factorization determined by cgeqlf (unblocked algorithm). slay.

🎀 Function/Subroutine Documentation 🎀

💅 subroutine zunm2l 💅

   subroutine zunm2l (character side, character trans, integer m, integer n,
       integer k, complex*16, dimension( lda, * ) a, integer lda, complex*16,
       dimension( * ) tau, complex*16, dimension( ldc, * ) c, integer ldc,
       complex*16, dimension( * ) work, integer info)

ZUNM2L multiplies a general matrix by the unitary matrix from a QL factorization determined by cgeqlf (unblocked algorithm).

🌟 Purpose 🌟

so here's the main character move: ZUNM2L overwrites the general complex m-by-n matrix C with

      Q * C  if SIDE = 'L' and TRANS = 'N', or

      Q**H* C  if SIDE = 'L' and TRANS = 'C', or

      C * Q  if SIDE = 'R' and TRANS = 'N', or

      C * Q**H if SIDE = 'R' and TRANS = 'C',

where Q is a complex unitary matrix defined as the product of k elementary reflectors

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

as returned by ZGEQLF. Q is of order m if SIDE = 'L' and of order n if SIDE = 'R'. periodt 💅

🌈 Parameters 🌈

• SIDE — SIDE is CHARACTER*1; = 'L': apply Q or Q**H from the Left; = 'R': apply Q or Q**H from the Right.
• TRANS — TRANS is CHARACTER*1; = 'N': apply Q (No transpose); = 'C': apply Q**H (Conjugate transpose).
• M — M is INTEGER; the number of rows of the matrix C. M >= 0.
• N — N is INTEGER; the number of columns of the matrix C. N >= 0.
• K — K is INTEGER; the number of elementary reflectors whose product defines the matrix Q. If SIDE = 'L', M >= K >= 0; if SIDE = 'R', N >= K >= 0.
• A — A is COMPLEX*16 array, dimension (LDA,K); the 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. A is modified by the routine but restored on exit.
• LDA — LDA is INTEGER; the leading dimension of the array A. If SIDE = 'L', LDA >= max(1,M); if SIDE = 'R', LDA >= max(1,N).
• 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.
• C — C is COMPLEX*16 array, dimension (LDC,N); on entry, the m-by-n matrix C. On exit, C is overwritten by Q*C or Q**H*C or C*Q**H or C*Q.
• LDC — LDC is INTEGER; the leading dimension of the array C. LDC >= max(1,M).
• WORK — WORK is COMPLEX*16 array, dimension (N) if SIDE = 'L', (M) if SIDE = 'R'.
• INFO — INFO is INTEGER; = 0: successful exit; < 0: if INFO = -i, the i-th argument had an illegal value.

👑 Author 👑

• Univ. of Tennessee
• Univ. of California Berkeley
• Univ. of Colorado Denver
• NAG Ltd.

Definition at line 157 of file zunm2l.f.

📜 Author 📜

Generated automatically by Doxygen for LAPACK from the source code.

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and that's the whole vibe, bestie: source/version checked, LAPACK Version 3.12.0, page SRC/zunm2l.f(3), all wrapped up with a bow 🎀✨💅