SRC/slasq1.f(3)

💖 NAME 💖

okay so SRC/slasq1.f(3) is the page title, and it comes from the Library Functions Manual. This page is about SRC/slasq1.f — specifically the slasq1 function/subroutine. That's the whole name section, bestie: a real one-subroutine situation. 💅

✨ SYNOPSIS ✨

Functions/Subroutines

subroutine slasq1 (n, d, e, work, info)

and the synopsis tea is literally: SLASQ1 computes the singular values of a real square bidiagonal matrix. Used by sbdsqr. 👑

🌸 Function/Subroutine Documentation 🌸

subroutine slasq1 (integer n, real, dimension( * ) d, real, dimension( * ) e, real, dimension( * ) work, integer info)

SLASQ1 computes the singular values of a real square bidiagonal matrix. Used by sbdsqr.

🎯 Purpose

okay so here's the purpose, and it's giving high-accuracy main character energy: SLASQ1 computes the singular values of a real N-by-N bidiagonal matrix with diagonal D and off-diagonal E. The singular values are computed to high relative accuracy, in the absence of denormalization, underflow and overflow. The algorithm was first presented in by K. V. Fernando and B. N. Parlett, Numer. Math., Vol-67, No. 2, pp. 191-230, 1994, and the present implementation is described in , LAPACK Working Note. 💖

🌈 Parameters

• N — N is INTEGER; it's the number of rows and columns in the matrix, and N >= 0.
• D — D is REAL array, dimension (N). On entry, D contains the diagonal elements of the bidiagonal matrix whose SVD is desired. On normal exit, D contains the singular values in decreasing order. 💖
• E — E is REAL array, dimension (N). On entry, elements E(1:N-1) contain the off-diagonal elements of the bidiagonal matrix whose SVD is desired. On exit, E is overwritten.
• WORK — WORK is REAL array, dimension (4*N).
• INFO — INFO is INTEGER.
  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value
  • > 0: the algorithm failed
    • = 1, a split was marked by a positive value in E
    • = 2, current block of Z not diagonalized after 100*N iterations (in inner while loop) On exit D and E represent a matrix with the same singular values which the calling subroutine could use to finish the computation, or even feed back into SLASQ1
    • = 3, termination criterion of outer while loop not met (program created more than N unreduced blocks)

👑 Author

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

Definition at line 107 of file slasq1.f.

💖 Author 💖

Generated automatically by Doxygen for LAPACK from the source code.

okay that's the whole page, bestie 🫶 — footer vibes: LAPACK, Version 3.12.0, page SRC/slasq1.f(3). No date is printed in the footer on this one, so that's all the official footer info we have. periodt 💅✨