SRC/DEPRECATED/zgeqpf.f(3)

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version 3.12.1 · 3 versions
, in arch rolling

🎀 SRC/DEPRECATED/zgeqpf.f 🎀

okay bestie, so this page lives in the LAPACK Library Functions Manual, and it's the glow-up guide for SRC/DEPRECATED/zgeqpf.f — yes, the DEPRECATED folder, we'll get to that, don't @ me yet 💅

✨ SYNOPSIS ✨

Functions/Subroutines

  • subroutine zgeqpf (m, n, a, lda, jpvt, tau, work, rwork, info) — ZGEQPF

🌸 Function/Subroutine Documentation 🌸

subroutine zgeqpf (integer m, integer n, complex*16, dimension( lda, * ) a,
    integer lda, integer, dimension( * ) jpvt, complex*16, dimension( * )
    tau, complex*16, dimension( * ) work, double precision, dimension( * )
    rwork, integer info)

ZGEQPF 👑

💖 Purpose 💖

This routine is deprecated and has been replaced by routine ZGEQP3.

not me telling you it's deprecated in the very first line 😭 okay but fr, it's still iconic:

ZGEQPF computes a QR factorization with column pivoting of a complex M-by-N matrix A: A*P = Q*R. slay 💅

🦋 Parameters 🦋

  • M — M is INTEGER. the number of rows of the matrix A, and M >= 0. no negatives, bestie, we don't do that here.
  • N — N is INTEGER. the number of columns of the matrix A, and N >= 0. same energy.
  • A — A is COMPLEX*16 array, dimension (LDA,N). On entry, the M-by-N matrix A. On exit, the upper triangle of the array contains the min(M,N)-by-N upper triangular matrix R; the elements below the diagonal, together with the array TAU, represent the unitary matrix Q as a product of min(m,n) elementary reflectors. it's giving before-and-after transformation ✨
  • LDA — LDA is INTEGER. the leading dimension of the array A, and LDA >= max(1,M). respect the constraint pls 🫶
  • JPVT — JPVT is INTEGER array, dimension (N). On entry, if JPVT(i) .ne. 0, the i-th column of A is permuted to the front of A*P (a leading column); if JPVT(i) = 0, the i-th column of A is a free column. On exit, if JPVT(i) = k, then the i-th column of A*P was the k-th column of A. the way it keeps receipts of every column's whole journey 😭 iconic
  • TAU — TAU is COMPLEX*16 array, dimension (min(M,N)). the scalar factors of the elementary reflectors.
  • WORK — WORK is COMPLEX*16 array, dimension (N).
  • RWORK — RWORK is DOUBLE PRECISION array, dimension (2*N).
  • 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.

the whole squad showed up for this one 🫶

🌈 Further Details: 🌈

The matrix Q is represented as a product of elementary reflectors

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

Each H(i) has the form

H = I - tau * v * v**H

where tau is a complex scalar, and v is a complex vector with v(1:i-1) = 0 and v(i) = 1; v(i+1:m) is stored on exit in A(i+1:m,i).

The matrix P is represented in jpvt as follows: If

jpvt(j) = i

then the jth column of P is the ith canonical unit vector. main character unit vector energy, honestly 🌟

Partial column norm updating strategy modified by

Z. Drmac and Z. Bujanovic, Dept. of Mathematics,
University of Zagreb, Croatia.
-- April 2011                                                      --

For more details see LAPACK Working Note 176. iykyk 🧚

Definition at line 147 of file zgeqpf.f.

⭐ Author ⭐

Generated automatically by Doxygen for LAPACK from the source code. (the robots did this one, not me 🙈)

ok so real talk: ZGEQPF is deprecated — the manpage says it plainly — and it's been replaced by routine ZGEQP3. if you're writing new code, go hang out with ZGEQP3 instead. no cap. 💀

mwah, that's the whole page bestie 💜 this cutie came from LAPACK Version 3.12.0, dated SRC/DEPRECATED/zgeqpf.f(3) — go forth and pivot those columns 🦋✨

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