SLACON(3)

SLACON(3) 💅✨

okay bestie, welcome to the Library Functions Manual page for SLACON(3) — yes, the manual-name tea is folded in right here at the top. This is the LAPACK Fortran bestie who estimates a 1-norm by making you do the matrix-vector products. Reverse communication icon behavior, fr fr.

🌸 NAME 🌸

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/slacon.f

That's the path, exactly as the page says. No cap.

🦋 SYNOPSIS 🦋

Functions/Subroutines

subroutine SLACON (n, v, x, isgn, est, kase)

SLACON estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.

🎀 Function/Subroutine Documentation 🎀

subroutine SLACON (integer n, real, dimension( * ) v, real, dimension( * )
    x, integer, dimension( * ) isgn, real est, integer kase)

SLACON estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.

💖 Purpose 💖

SLACON estimates the 1-norm of a square, real matrix A. Reverse communication is used for evaluating matrix-vector products. That's the whole purpose, and it ate.

✨ Parameters ✨

N

N is INTEGER. It's the order of the matrix. N >= 1.

V

V is REAL array, dimension (N). On the final return, V = A*W, where EST = norm(V)/norm(W) (W is not returned). Not me getting attached to a vector that literally does not come back 😭.

X

X is REAL array, dimension (N). On an intermediate return, X should be overwritten by

A * X,   if KASE=1,
A**T * X,  if KASE=2,

and SLACON must be re-called with all the other parameters unchanged. Periodt.

ISGN

ISGN is INTEGER array, dimension (N). That's the note. Short and iconic.

EST

EST is REAL. On entry with KASE = 1 or 2 and JUMP = 3, EST should be unchanged from the previous call to SLACON. On exit, EST is an estimate (a lower bound) for norm(A). Lowkey crucial.

KASE

KASE is INTEGER. On the initial call to SLACON, KASE should be 0. On an intermediate return, KASE will be 1 or 2, indicating whether X should be overwritten by A * X or A**T * X. On the final return from SLACON, KASE will again be 0. The communication is reversing, bestie.

👑 Author 👑

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

🫶 Contributors 🫶

• Nick Higham, University of Manchester.
• Originally named SONEST, dated March 16, 1988.

📚 References 📚

N.J. Higham, "FORTRAN codes for estimating the one-norm ofa real or complex matrix, with applications to condition estimation", ACM Trans. Math. Soft., vol. 14, no. 4, pp. 381-396, December 1988.

bestie, yes the quote says ofa — I am keeping it exactly as the page has it. Character-for-character, no editing the source tea. 💅

📍 Definition at line 114 of file slacon.f. 📍

Literally that: definition at line 114 of file slacon.f.

👑 Author (the Doxygen encore) 👑

Generated automatically by Doxygen for LAPACK from the source code.

---

cute sign-off: this page was served by LAPACK Version 3.12.0, from /home/abui...RC/slacon.f(3) — date? the footer does not list one, so I'm not inventing it, bestie. Mwah 💋✨