SRC/zunmqr.f(3)

🌸 NAME 🌸

okay bestie, this is SRC/zunmqr.f — the manual page for the zunmqr subroutine, and it comes from the Library Functions Manual. The header vibe is SRC/zunmqr.f(3), and we are keeping every single detail cute and intact. 💖

✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

• subroutine zunmqr (side, trans, m, n, k, a, lda, tau, c, ldc, work, lwork, info) — ZUNMQR

🦋 Function/Subroutine Documentation 🦋

Here's the full signature in all its glory, bestie:

subroutine zunmqr (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 lwork, integer info)

This icon is literally ZUNMQR. 👑

✨ Purpose ✨

ZUNMQR overwrites the general complex M-by-N matrix C with:

                SIDE = 'L'     SIDE = 'R'
TRANS = 'N':      Q * C          C * Q
TRANS = 'C':      Q**H * C       C * Q**H

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

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

as returned by ZGEQRF. Q is of order M if SIDE = 'L' and of order N if SIDE = 'R'. That's the whole purpose, no cap. 💫

🎀 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': No transpose, apply Q;
• = 'C': Conjugate transpose, apply Q**H.

💅 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 ZGEQRF in the first k columns of its array argument A.

💅 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 ZGEQRF.

💅 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 (MAX(1,LWORK)).
• On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

💅 LWORK

• LWORK is INTEGER.
• The dimension of the array WORK.
• If SIDE = 'L', LWORK >= max(1,N);
• if SIDE = 'R', LWORK >= max(1,M).
• For good performance, LWORK should generally be larger.
• 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.

bestie, the LWORK = -1 workspace-query situation is real: it 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 had an illegal value.

💜 Author 💜

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

Definition at line 165 of file zunmqr.f.

✨ Author ✨

Generated automatically by Doxygen for LAPACK from the source code.

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kiss kiss 💋 — LAPACK Version 3.12.0, SRC/zunmqr.f(3), that's the footer vibe. bye bestie 🫶