SRC/cungql.f(3)

💖 SRC/cungql.f 💖

okay bestie, we're in the Library Functions Manual, and this is the page for SRC/cungql.f — the CUNGQL subroutine. Grab your iced coffee, because we're doing complex linear algebra and it's honestly iconic. ✨

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🎀 NAME 🎀

SRC/cungql.f — that's the name, periodt. 💅

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✨ SYNOPSIS ✨

🦋 Functions/Subroutines 🦋

• subroutine cungql (m, n, k, a, lda, tau, work, lwork, info) — CUNGQL

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💅 Function/Subroutine Documentation 💅

Here's the full signature, bestie — every type and dimension exactly as it appears:

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

CUNGQL 🫶

🫶 Purpose 🫶

Okay so CUNGQL generates an M-by-N complex matrix Q with orthonormal columns. That matrix Q is defined as the last N columns of a product of K elementary reflectors of order M, like:

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

...as returned by CGEQLF. Slay. 💖

🌈 Parameters 🌈

M

M is INTEGER. It's the number of rows of the matrix Q. Constraint: M >= 0. No cap.

N

N is INTEGER. It's the number of columns of the matrix Q. Constraint: M >= N >= 0.

K

K is INTEGER. It's the number of elementary reflectors whose product defines the matrix Q. Constraint: N >= K >= 0.

A

A is a 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, it holds the M-by-N matrix Q. 💅

LDA

LDA is INTEGER. It's the first dimension of the array A. Constraint: LDA >= max(1,M).

TAU

TAU is a COMPLEX array, dimension (K). TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by CGEQLF.

WORK

WORK is a COMPLEX array, dimension (MAX(1,LWORK)). On exit, if INFO = 0, WORK(1) returns the optimal LWORK. 🫶

LWORK

LWORK is INTEGER. It's the dimension of the array WORK. Constraint: LWORK >= max(1,N). For optimum performance, LWORK >= N*NB, where NB is the optimal blocksize.

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. Important!! ⚠️

INFO

INFO is INTEGER.

• = 0: successful exit — we love a clean win. ✅
• < 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 127 of file cungql.f.

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⭐ Author ⭐ (generated edition)

Generated automatically by Doxygen for LAPACK from the source code.

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That's the whole page, bestie! Sending you off with LAPACK Version 3.12.0 and this page from SRC/cungql.f(3) — mwah 💋✨