SRC/dlartgs.f(3)

✨ NAME ✨

Okay bestie, welcome to the Library Functions Manual page for SRC/dlartgs.f — the home of dlartgs, a Fortran subroutine that understood the assignment: generate a plane rotation designed to introduce a bulge in implicit QR iteration for the bidiagonal SVD problem. 👑

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🦋 SYNOPSIS 🦋

✨ Functions/Subroutines ✨

• subroutine dlartgs (x, y, sigma, cs, sn) — DLARTGS generates a plane rotation designed to introduce a bulge in implicit QR iteration for the bidiagonal SVD problem.

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🌸 Function/Subroutine Documentation 🌸

subroutine dlartgs (double precision x, double precision y, double precision sigma, double precision cs, double precision sn)

🎀 Purpose 🎀

So like, DLARTGS generates a plane rotation designed to introduce a bulge in Golub-Reinsch-style implicit QR iteration for the bidiagonal SVD problem. X and Y are the top-row entries, and SIGMA is the shift. The computed CS and SN define a plane rotation satisfying

   [  CS  SN  ]  .  [ X^2 - SIGMA ]  =  [ R ],
   [ -SN  CS  ]     [    X * Y    ]     [ 0 ]

with R nonnegative. If X^2 - SIGMA and X * Y are 0, then the rotation is by PI/2. Literally the whole point. 🫶

🌸 Parameters 🌸

• X — X is DOUBLE PRECISION. The (1,1) entry of an upper bidiagonal matrix.
• Y — Y is DOUBLE PRECISION. The (1,2) entry of an upper bidiagonal matrix.
• SIGMA — SIGMA is DOUBLE PRECISION. The shift.
• CS — CS is DOUBLE PRECISION. The cosine of the rotation.
• SN — SN is DOUBLE PRECISION. The sine of the rotation.

🫶 Author 🫶

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

Definition at line 89 of file dlartgs.f.

👑 Author 👑

Generated automatically by Doxygen for LAPACK from the source code.

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Okay bestie, that’s the whole page. The footer is serving source/version realness: LAPACK, Version 3.12.0, page SRC/dlartgs.f(3). No date in the footer, so we’re not making one up — periodt. 💜🎀