SRC/claqp2.f(3)

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version 3.12.1 · 4 versions
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🎀 SRC/claqp2.f 🎀

Okay bestie, welcome to the Library Functions Manual page for SRC/claqp2.f(3) — yes, the manual name is folded in right here because we’re doing this cute-style, not copy-paste-style. 💖

🌸 NAME 🌸

SRC/claqp2.f — the LAPACK routine page, serving main-character linear algebra energy. ✨

🦋 SYNOPSIS 🦋

Functions/Subroutines

subroutine claqp2 (m, n, offset, a, lda, jpvt, tau, vn1, vn2, work)
    CLAQP2 computes a QR factorization with column pivoting of the matrix block.

👑 Function/Subroutine Documentation 👑

💅 subroutine claqp2 💅

subroutine claqp2 (integer m, integer n, integer offset, complex, dimension(
    lda, * ) a, integer lda, integer, dimension( * ) jpvt, complex,
    dimension( * ) tau, real, dimension( * ) vn1, real, dimension( * ) vn2,
    complex, dimension( * ) work)

CLAQP2 computes a QR factorization with column pivoting of the matrix block. It’s giving “I know my block, and I know my pivots.” 🔥

🍓 Purpose 🍓

So here’s the tea: CLAQP2 computes a QR factorization with column pivoting of the block A(OFFSET+1:M,1:N). The block A(1:OFFSET,1:N) gets pivoted accordingly, but it is not factorized. Periodt. 💅

🌈 Parameters 🌈

  • M — M is INTEGER. Number of rows of the matrix A. M >= 0.
  • N — N is INTEGER. Number of columns of the matrix A. N >= 0.
  • OFFSET — OFFSET is INTEGER. The number of rows of the matrix A that must be pivoted but not factorized. OFFSET >= 0.
  • A — A is COMPLEX array, dimension (LDA,N). On entry, it’s the M-by-N matrix A. On exit, the upper triangle of block A(OFFSET+1:M,1:N) is the triangular factor obtained; the elements in block A(OFFSET+1:M,1:N) below the diagonal, together with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors. Block A(1:OFFSET,1:N) has been accordingly pivoted, but not factorized.
  • LDA — LDA is INTEGER. The leading dimension of the array A. LDA >= max(1,M).
  • 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.
  • TAU — TAU is COMPLEX array, dimension (min(M,N)). The scalar factors of the elementary reflectors.
  • VN1 — VN1 is REAL array, dimension (N). The vector with the partial column norms.
  • VN2 — VN2 is REAL array, dimension (N). The vector with the exact column norms.
  • WORK — WORK is COMPLEX array, dimension (N).

🧚 Author 🧚

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

💜 Contributors 💜

  • G. Quintana-Orti, Depto. de Informatica, Universidad Jaime I, Spain
  • X. Sun, Computer Science Dept., Duke University, USA
  • Partial column norm updating strategy modified on April 2011 Z. Drmac and Z. Bujanovic, Dept. of Mathematics, University of Zagreb, Croatia.

📚 References 📚

  • LAPACK Working Note 176

📍 Definition 📍

Definition at line 147 of file claqp2.f.

🤖 Author (the Doxygen one) 🤖

Generated automatically by Doxygen for LAPACK from the source code.

💖 Cute little sign-off: this whole vibe is from LAPACK, Version 3.12.0, and it’s the manual page for SRC/claqp2.f(3). Bye bestie, go pivot slayfully! 💅✨
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