DLAED5(3)

💖 NAME 💖

Hey bestie 🫶 welcome to DLAED5(3) from the LAPACK Library Functions Manual. This page is all about this one file path: /home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/dlaed5.f ✨

✨ SYNOPSIS ✨

🧚 Functions/Subroutines

subroutine DLAED5 (i, d, z, delta, rho, dlam)
    DLAED5 used by DSTEDC. Solves the 2-by-2 secular equation.

🌸 Function/Subroutine Documentation 🌸

subroutine DLAED5 (integer i, double precision, dimension( 2 ) d, double
    precision, dimension( 2 ) z, double precision, dimension( 2 ) delta,
    double precision rho, double precision dlam)

DLAED5 used by DSTEDC. Solves the 2-by-2 secular equation.

🎀 Purpose 🎀

Okay so this subroutine computes the I-th eigenvalue of a symmetric rank-one modification of a 2-by-2 diagonal matrix:

diag( D )  +  RHO * Z * transpose(Z) .

The diagonal elements in the array D are assumed to satisfy:

D(i) < D(j)  for  i < j .

We also assume RHO > 0 and that the Euclidean norm of the vector Z is one. Periodt. 💅

👑 Parameters 👑

• I — I is INTEGER. The index of the eigenvalue to be computed. I = 1 or I = 2.
• D — D is DOUBLE PRECISION array, dimension (2). The original eigenvalues. We assume D(1) < D(2).
• Z — Z is DOUBLE PRECISION array, dimension (2). The components of the updating vector.
• DELTA — DELTA is DOUBLE PRECISION array, dimension (2). The vector DELTA contains the information necessary to construct the eigenvectors.
• RHO — RHO is DOUBLE PRECISION. The scalar in the symmetric updating formula.
• DLAM — DLAM is DOUBLE PRECISION. The computed lambda_I, the I-th updated eigenvalue.

🌟 Author 🌟

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

🦋 Contributors: 🦋

Ren-Cang Li, Computer Science Division, University of California at Berkeley, USA

📍 Definition at line 107 of file dlaed5.f. 📍

That's literally where it's defined, bestie. 🫶

🎀 Author 🎀

Generated automatically by Doxygen for LAPACK from the source code.

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That's the whole page, bestie 🫶 — LAPACK Version 3.12.0, footer path /home/abui...RC/dlaed5.f(3). Mwah! 💖