SRC/zlacn2.f(3)

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version 3.12.1 · 4 versions
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💖 NAME 💖

SRC/zlacn2.f — from the Library Functions Manual, bestie. This is the ZLACN2 page and it’s lowkey iconic. ✨

✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

subroutine zlacn2 (n, v, x, est, kase, isave)

ZLACN2 estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products. 💅

🫶 Function/Subroutine Documentation 🫶

subroutine zlacn2 (integer n, complex*16, dimension( * ) v, complex*16,
       dimension( * ) x, double precision est, integer kase, integer,
       dimension( 3 ) isave)

ZLACN2 estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products. No cap.

🌸 Purpose 🌸

ZLACN2 estimates the 1-norm of a square, complex matrix A. Reverse communication is used for evaluating matrix-vector products. Periodt. 💜

🎀 Parameters 🎀

  • N — N is INTEGER. The order of the matrix. N >= 1.
  • V — V is COMPLEX*16 array, dimension (N). On the final return, V = A*W, where EST = norm(V)/norm(W) (W is not returned).
  • X — X is COMPLEX*16 array, dimension (N). On an intermediate return, X should be overwritten by
A * X,   if KASE=1,
A**H * X,  if KASE=2,

where A**H is the conjugate transpose of A, and ZLACN2 must be re-called with all the other parameters unchanged.

  • EST — EST is DOUBLE PRECISION. On entry with KASE = 1 or 2 and ISAVE(1) = 3, EST should be unchanged from the previous call to ZLACN2. On exit, EST is an estimate (a lower bound) for norm(A).
  • KASE — KASE is INTEGER. On the initial call to ZLACN2, 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**H * X. On the final return from ZLACN2, KASE will again be 0.
  • ISAVE — ISAVE is INTEGER array, dimension (3). ISAVE is used to save variables between calls to ZLACN2.

👑 Author 👑

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

💀 Further Details 💀

  • Originally named CONEST, dated March 16, 1988.
  • Last modified: April, 1999.
  • This is a thread safe version of ZLACON, which uses the array ISAVE in place of a SAVE statement, as follows:
ZLACON     ZLACN2
 JUMP     ISAVE(1)
 J        ISAVE(2)
 ITER     ISAVE(3)

🦋 Contributors 🦋

Nick Higham, University of Manchester.

🍓 References 🍓

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

Definition at line 132 of file zlacn2.f.

That’s the whole page, bestie!! Footer vibe check: LAPACK, Version 3.12.0, source SRC/zlacn2.f(3) — generated automatically by Doxygen for LAPACK from the source code. 💖✨🎀

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