DLASQ4(3)

📦 version 3.12.0, in opensuse-leap 16.0

💖 DLASQ4(3) 💖

okay so this one is straight outta the Library Functions Manual, and it’s giving “tiny eigenvalue approximation subroutine that absolutely knows what it’s doing.” 💅

🌸 NAME 🌸

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/dlasq4.f

That’s the file, bestie. That’s the whole NAME moment. 🎀

✨ SYNOPSIS ✨

Functions/Subroutines

subroutine DLASQ4 (i0, n0, z, pp, n0in, dmin, dmin1, dmin2, dn, dn1,
    dn2, tau, ttype, g)

DLASQ4 computes an approximation to the smallest eigenvalue using values of d from the previous transform. Used by sbdsqr. 🔥

🦋 Function/Subroutine Documentation 🦋

subroutine DLASQ4 (integer i0, integer n0, double precision, dimension( * )
    z, integer pp, integer n0in, double precision dmin, double precision
    dmin1, double precision dmin2, double precision dn, double precision
    dn1, double precision dn2, double precision tau, integer ttype, double
    precision g)

DLASQ4 computes an approximation to the smallest eigenvalue using values of d from the previous transform. Used by sbdsqr. Literally its whole main-character job. 🌟

Purpose:

DLASQ4 computes an approximation TAU to the smallest eigenvalue using values of d from the previous transform. No cap, that’s the purpose. 💜

Parameters

I0

I0 is INTEGER.

First index.

N0

N0 is INTEGER.

Last index.

Z

Z is DOUBLE PRECISION array, dimension ( 4*N0 ).

Z holds the qd array.

PP

PP is INTEGER.

PP=0 for ping, PP=1 for pong.

N0IN

N0IN is INTEGER.

The value of N0 at start of EIGTEST.

DMIN

DMIN is DOUBLE PRECISION.

Minimum value of d.

DMIN1

DMIN1 is DOUBLE PRECISION.

Minimum value of d, excluding D( N0 ).

DMIN2

DMIN2 is DOUBLE PRECISION.

Minimum value of d, excluding D( N0 ) and D( N0-1 ).

DN

DN is DOUBLE PRECISION.

d(N)

DN1

DN1 is DOUBLE PRECISION.

d(N-1)

DN2

DN2 is DOUBLE PRECISION.

d(N-2)

TAU

TAU is DOUBLE PRECISION.

This is the shift.

TTYPE

TTYPE is INTEGER.

Shift type.

G

G is DOUBLE PRECISION.

G is passed as an argument in order to save its value between calls to DLASQ4. Slay, honestly. 🫶

Author

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

Further Details:

CNST1 = 9/16

Definition at line 149 of file dlasq4.f.

Author

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okay that’s the whole page, bestie — LAPACK Version 3.12.0, aka /home/abui...RC/dlasq4.f(3), signing off with immaculate Fortran energy. 💖✨🎀🦋

📦 where this page comes from