SLAQP2(3)

💅 SLAQP2(3) 💅

okay bestie, this is the Library Functions Manual entry for SLAQP2(3) — and no cap, it's a Fortran subroutine that computes a QR factorization with column pivoting of a matrix block. Let's get into it. 🫶

✨ NAME ✨

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/slaqp2.f

🌸 SYNOPSIS 🌸

Functions/Subroutines

• subroutine SLAQP2 (m, n, offset, a, lda, jpvt, tau, vn1, vn2, work) — SLAQP2 computes a QR factorization with column pivoting of the matrix block.

🦋 Function/Subroutine Documentation 🦋

Here's the whole signature, exactly as the page gives it:

   subroutine SLAQP2 (integer m, integer n, integer offset, real, dimension(
       lda, * ) a, integer lda, integer, dimension( * ) jpvt, real, dimension(
       * ) tau, real, dimension( * ) vn1, real, dimension( * ) vn2, real,
       dimension( * ) work)

SLAQP2 computes a QR factorization with column pivoting of the matrix block.

💡 Purpose

SLAQP2 computes a QR factorization with column pivoting of the block A(OFFSET+1:M,1:N). The block A(1:OFFSET,1:N) is accordingly pivoted, but not factorized.

🎀 Parameters

• M — M is INTEGER. The number of rows of the matrix A. M >= 0.
• N — N is INTEGER. The 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 REAL array, dimension (LDA,N). On entry, 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 REAL 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 REAL 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 at line 147 of file slaqp2.f.

🧚 Author 🧚

Generated automatically by Doxygen for LAPACK from the source code.

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bye bestie! this lil page is from the LAPACK Version 3.12.0 manual, and its footer path is /home/abui...RC/slaqp2.f(3). mwah 💖