CGSVJ0(3)

💖 CGSVJ0(3) — Library Functions Manual 💖

okay bestie, welcome to the Library Functions Manual page for cgsvj0.f(3) ✨ this is the whole vibe: a Fortran subroutine that pre-processes for cgesvj, with zero gatekeeping. 🫶

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💅 NAME 💅

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/cgsvj0.f

That’s the name, literally. No cap. 💀

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🌸 SYNOPSIS 🌸

🌈 Functions/Subroutines 🌈

subroutine CGSVJ0 (jobv, m, n, a, lda, d, sva, mv, v, ldv, eps, sfmin,
    tol, nsweep, work, lwork, info)

CGSVJ0 pre-processor for the routine cgesvj.

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🦋 Function/Subroutine Documentation 🦋

subroutine CGSVJ0 (character*1 jobv, integer m, integer n, complex,
    dimension( lda, * ) a, integer lda, complex, dimension( n ) d, real,
    dimension( n ) sva, integer mv, complex, dimension( ldv, * ) v, integer
    ldv, real eps, real sfmin, real tol, integer nsweep, complex, dimension(
    lwork ) work, integer lwork, integer info)

CGSVJ0 pre-processor for the routine cgesvj.

✨ Purpose ✨

CGSVJ0 is called from CGESVJ as a pre-processor and that is its main purpose. It applies Jacobi rotations in the same way as CGESVJ does, but it does not check convergence (stopping criterion). Few tuning parameters (marked by [TP]) are available for the implementer. 💫

🎀 Parameters 🎀

• JOBV — JOBV is CHARACTER*1. Specifies whether the output from this procedure is used to compute the matrix V:
  • = 'V': the product of the Jacobi rotations is accumulated by postmultiplying the N-by-N array V. (See the description of V.)
  • = 'A': the product of the Jacobi rotations is accumulated by postmultiplying the MV-by-N array V. (See the descriptions of MV and V.)
  • = 'N': the Jacobi rotations are not accumulated.
• M — M is INTEGER. The number of rows of the input matrix A. M >= 0.
• N — N is INTEGER. The number of columns of the input matrix A. M >= N >= 0.
• A — A is COMPLEX array, dimension (LDA,N). On entry, M-by-N matrix A, such that A*diag(D) represents the input matrix. On exit, A_onexit * diag(D_onexit) represents the input matrix A*diag(D) post-multiplied by a sequence of Jacobi rotations, where the rotation threshold and the total number of sweeps are given in TOL and NSWEEP, respectively. (See the descriptions of D, TOL and NSWEEP.)
• LDA — LDA is INTEGER. The leading dimension of the array A. LDA >= max(1,M).
• D — D is COMPLEX array, dimension (N). The array D accumulates the scaling factors from the complex scaled Jacobi rotations. On entry, A*diag(D) represents the input matrix. On exit, A_onexit*diag(D_onexit) represents the input matrix post-multiplied by a sequence of Jacobi rotations, where the rotation threshold and the total number of sweeps are given in TOL and NSWEEP, respectively. (See the descriptions of A, TOL and NSWEEP.)
• SVA — SVA is REAL array, dimension (N). On entry, SVA contains the Euclidean norms of the columns of the matrix A*diag(D). On exit, SVA contains the Euclidean norms of the columns of the matrix A_onexit*diag(D_onexit).
• MV — MV is INTEGER. If JOBV = 'A', then MV rows of V are post-multiplied by a sequence of Jacobi rotations. If JOBV = 'N', then MV is not referenced.
• V — V is COMPLEX array, dimension (LDV,N). If JOBV = 'V' then N rows of V are post-multiplied by a sequence of Jacobi rotations. If JOBV = 'A' then MV rows of V are post-multiplied by a sequence of Jacobi rotations. If JOBV = 'N', then V is not referenced.
• LDV — LDV is INTEGER. The leading dimension of the array V, LDV >= 1. If JOBV = 'V', LDV >= N. If JOBV = 'A', LDV >= MV.
• EPS — EPS is REAL. EPS = SLAMCH('Epsilon').
• SFMIN — SFMIN is REAL. SFMIN = SLAMCH('Safe Minimum').
• TOL — TOL is REAL. TOL is the threshold for Jacobi rotations. For a pair A(:,p), A(:,q) of pivot columns, the Jacobi rotation is applied only if ABS(COS(angle(A(:,p),A(:,q)))) > TOL.
• NSWEEP — NSWEEP is INTEGER. NSWEEP is the number of sweeps of Jacobi rotations to be performed.
• WORK — WORK is COMPLEX array, dimension (LWORK).
• LWORK — LWORK is INTEGER. LWORK is the dimension of WORK. LWORK >= M.
• INFO — INFO is INTEGER.
  • = 0: successful exit.
  • < 0: if INFO = -i, then the i-th argument had an illegal value.

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🫶 Author 🫶

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

🦋 Further Details 🦋

CGSVJ0 is used just to enable CGESVJ to call a simplified version of itself to work on a submatrix of the original matrix.

🌟 Contributor 🌟

Zlatko Drmac (Zagreb, Croatia)

🙈 Bugs, Examples and Comments 🙈

Please report all bugs and send interesting test examples and comments to drmac@math.hr. Thank you.

📍 Definition at line 216 of file cgsvj0.f.

💜 Author 💜

Generated automatically by Doxygen for LAPACK from the source code.

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okay that’s the whole manual, bestie 🫶💖 — LAPACK Version 3.12.0, footer path /home/abui...RC/cgsvj0.f(3), and yes, you ate this documentation. Periodt. 👑✨