SRC/slasq3.f(3)

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version 3.12.1 · 7 versions
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💅 SRC/slasq3.f(3) — main character energy 💅

Hey bestie 🫶, this is the Library Functions Manual page for SRC/slasq3.f, and it's honestly giving “tiny subroutine, big responsibilities” ✨. No cap, every parameter and note is still here.

📛 NAME 📛

SRC/slasq3.f

✨ SYNOPSIS ✨

🧩 Functions/Subroutines 🧩

subroutine slasq3 (i0, n0, z, pp, dmin, sigma, desig, qmax, nfail, iter, ndiv, ieee, ttype, dmin1, dmin2, dn, dn1, dn2, g, tau)
  • What it does: SLASQ3 checks for deflation, computes a shift and calls dqds. Used by sbdsqr.

🛠️ Function/Subroutine Documentation 🛠️

🧚 subroutine slasq3 🧚

subroutine slasq3 (integer i0, integer n0, real, dimension( * ) z, integer pp, real dmin, real sigma, real desig, real qmax, integer nfail, integer iter, integer ndiv, logical ieee, integer ttype, real dmin1, real dmin2, real dn, real dn1, real dn2, real g, real tau)

SLASQ3 is the one checking for deflation, computing a shift, and calling dqds. It's used by sbdsqr.

🎯 Purpose 🎯

SLASQ3 checks for deflation, computes a shift (TAU) and calls dqds. In case of failure it changes shifts, and tries again until output is positive.

🌸 Parameters 🌸

  • I0 — I0 is INTEGER. First index.
  • N0 — N0 is INTEGER. Last index.
  • Z — Z is REAL array, dimension ( 4*N0 ). Z holds the qd array.
  • PP — PP is INTEGER. PP=0 for ping, PP=1 for pong. PP=2 indicates that flipping was applied to the Z array and that the initial tests for deflation should not be performed.
  • DMIN — DMIN is REAL. Minimum value of d.
  • SIGMA — SIGMA is REAL. Sum of shifts used in current segment.
  • DESIG — DESIG is REAL. Lower order part of SIGMA.
  • QMAX — QMAX is REAL. Maximum value of q.
  • NFAIL — NFAIL is INTEGER. Increment NFAIL by 1 each time the shift was too big.
  • ITER — ITER is INTEGER. Increment ITER by 1 for each iteration.
  • NDIV — NDIV is INTEGER. Increment NDIV by 1 for each division.
  • IEEE — IEEE is LOGICAL. Flag for IEEE or non IEEE arithmetic (passed to SLASQ5).
  • TTYPE — TTYPE is INTEGER. Shift type.
  • DMIN1 — DMIN1 is REAL.
  • DMIN2 — DMIN2 is REAL.
  • DN — DN is REAL.
  • DN1 — DN1 is REAL.
  • DN2 — DN2 is REAL.
  • G — G is REAL.
  • TAU — TAU is REAL. These are passed as arguments in order to save their values between calls to SLASQ3.

👑 Author 👑

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

Definition at line 179 of file slasq3.f.

🤖 Author 🤖

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Signed, sealed, delivered 💌: LAPACK Version 3.12.0, from SRC/slasq3.f(3) — stay slay and may your shifts always be positive 💖✨🦋

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