TESTING/EIG/dslect.f(3)

📦
version 3.12.1 · 3 versions
, in arch rolling

💅 TESTING/EIG/dslect.f ✨

okay so bestie, gather round, because this page is from LAPACK, and the file we're talking about is TESTING/EIG/dslect.f — like, the header up there literally says TESTING/EIG/dslect.f(3), and the manual it lives in is Library Functions Manual 🎀 so that's the whole vibe. she's a testing-file girlie and she's here to sort eigenvalues. no cap.

🌸 SYNOPSIS 🌸

Functions/Subroutines 🦋

  • logical function dslect (zr, zi) — DSLECT, that's her 🫶

✨ Function/Subroutine Documentation ✨

logical function dslect (double precision zr, double precision zi)

DSLECT 💖 (yes, again, she's the whole moment)

🎀 Purpose 🎀

fortran !> !> DSLECT returns .TRUE. if the eigenvalue ZR+sqrt(-1)*ZI is to be !> selected, and otherwise it returns .FALSE. !> It is used by DCHK41 to test if DGEES successfully sorts eigenvalues, !> and by DCHK43 to test if DGEESX successfully sorts eigenvalues. !> !> The common block /SSLCT/ controls how eigenvalues are selected. !> If SELOPT = 0, then DSLECT return .TRUE. when ZR is less than zero, !> and .FALSE. otherwise. !> If SELOPT is at least 1, DSLECT returns SELVAL(SELOPT) and adds 1 !> to SELOPT, cycling back to 1 at SELMAX. !>

so, like, to translate the girl-talk: our bestie DSLECT returns .TRUE. if the eigenvalue ZR+sqrt(-1)*ZI is supposed to be selected, and .FALSE. if she's not the one 💅. she gets called up by DCHK41 to check whether DGEES actually sorts eigenvalues correctly, and by DCHK43 to check the same thing for DGEESX — she's the vibe-checker for the sorting, literally.

the common block /SSLCT/ is what tells her how eigenvalues get selected 🧚:

  • if SELOPT = 0, she returns .TRUE. when ZR is less than zero, and .FALSE. otherwise.
  • if SELOPT is at least 1, she returns SELVAL(SELOPT) and adds 1 to SELOPT, cycling back to 1 at SELMAX. iconic behavior honestly, she just keeps looping 🔥

⭐ Parameters ⭐

ZR

fortran !> ZR is DOUBLE PRECISION !> The real part of a complex eigenvalue ZR + i*ZI. !>

ZR is DOUBLE PRECISION, and she's the real part of the complex eigenvalue ZR + i*ZI 😌

ZI

fortran !> ZI is DOUBLE PRECISION !> The imaginary part of a complex eigenvalue ZR + i*ZI. !>

ZI is also DOUBLE PRECISION, and she's the imaginary part of that same complex eigenvalue ZR + i*ZI 💜

👑 Author 👑

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

the whole squad came through for this one, fr fr 🌈

Definition at line 61 of file dslect.f. 📍

🌸 Author 🌸

Generated automatically by Doxygen for LAPACK from the source code. so nobody hand-wrote this, the machine did it, and honestly? she ate 🤖💅

okay that's the whole page bestie, love that for us 💖 and for the cute sign-off: this is LAPACK Version 3.12.0, dated with that TESTING/EIG/dslect.f(3) footer energy at the very bottom, iykyk 🫶✨🎀

📦 where this page comes from