SGSVJ0(3)

📦 version 3.12.0, in opensuse-leap 16.0

💅 SGSVJ0(3) — Library Functions Manual 💅

okay so real talk: this is the man page for SGSVJ0(3) from the Library Functions Manual, and the source file it's repping is:

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/sgsvj0.f

✨ SYNOPSIS ✨

Functions/Subroutines

bestie, here's the callable vibe:

subroutine SGSVJ0 (jobv, m, n, a, lda, d, sva, mv, v, ldv, eps, sfmin,
    tol, nsweep, work, lwork, info)
    SGSVJ0 pre-processor for the routine sgesvj.

🦋 Function/Subroutine Documentation 🦋

the full signature, character for character:

subroutine SGSVJ0 (character*1 jobv, integer m, integer n, real, dimension(
    lda, * ) a, integer lda, real, dimension( n ) d, real, dimension( n )
    sva, integer mv, real, dimension( ldv, * ) v, integer ldv, real eps,
    real sfmin, real tol, integer nsweep, real, dimension( lwork ) work,
    integer lwork, integer info)
    SGSVJ0 pre-processor for the routine sgesvj.

Purpose

okay so the main-character purpose is literally this: SGSVJ0 is called from SGESVJ as a pre-processor, and that's its whole main job. It applies Jacobi rotations in the same way as SGESVJ does, but it does not check convergence — like, no stopping criterion, none, zero. A few tuning parameters (marked by [TP]) are available for the implementer. 🎀

🎀 Parameters 🎀

JOBV

JOBV is CHARACTER*1. It 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 REAL array, dimension (LDA,N).

On entry, M-by-N matrix A, such that A*diag(D) represents the input matrix.

On exit, A_onexit * 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 REAL array, dimension (N).

The array D accumulates the scaling factors from the fast 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 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 REAL 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 REAL 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.

👑 Author 👑

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

🌈 Further Details:

SGSVJ0 is used just to enable SGESVJ to call a simplified version of itself to work on a submatrix of the original matrix.

🫶 Contributors:

Zlatko Drmac (Zagreb, Croatia) and Kresimir Veselic (Hagen, Germany)

💌 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 sgsvj0.f.

Author ✨

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k bye bestie 💖 this was SGSVJ0(3) from LAPACK Version 3.12.0, with the footer sourced from /home/abui...RC/sgsvj0.f(3) — mwah, stay slaying ✨

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