SRC/clacn2.f(3)

💖 SRC/clacn2.f(3) 💖

okay bestie, this page comes from the Library Functions Manual, and it’s literally the clacn2 subroutine’s whole personality. We’re keeping every detail, no cap. 🫶

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🌸 NAME 🌸

SRC/clacn2.f — the file that serves up clacn2, the 1-norm estimator with reverse-communication main-character energy. 💅

✨ SYNOPSIS ✨

🧚 Functions/Subroutines

• subroutine clacn2 (n, v, x, est, kase, isave) — CLACN2 estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.

🫶 Function/Subroutine Documentation 🫶

subroutine clacn2 (integer n, complex, dimension( * ) v, complex, dimension(
     * ) x, real est, integer kase, integer, dimension( 3 ) isave)

CLACN2 estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products. That’s the headline, and it’s giving exactly what it needs to give. ✨

🎯 Purpose

CLACN2 estimates the 1-norm of a square, complex matrix A. Reverse communication is used for evaluating matrix-vector products. That’s the whole assignment, and it ate. 💜

🧸 Parameters

• N — N is INTEGER. The order of the matrix. N >= 1. 🎀
• V — V is COMPLEX array, dimension (N). On the final return, V = A*W, where EST = norm(V)/norm(W) (W is not returned). She’s not returned, bestie. 💀
• X — X is COMPLEX 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 CLACN2 must be re-called with all the other parameters unchanged. 🌀
• EST — EST is REAL. On entry with KASE = 1 or 2 and ISAVE(1) = 3, EST should be unchanged from the previous call to CLACN2. On exit, EST is an estimate (a lower bound) for norm(A). Lower bound, not a delusion. 💅
• KASE — KASE is INTEGER. On the initial call to CLACN2, 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 CLACN2, KASE will again be 0. The reverse-communication baton pass, periodt. 🏃‍♀️
• ISAVE — ISAVE is INTEGER array, dimension (3). ISAVE is used to save variables between calls to SLACN2. 🫶

👑 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 CLACON, which uses the array ISAVE in place of a SAVE statement, as follows:

CLACON     CLACN2
 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 clacn2.f.

🧚 Author 🧚

Generated automatically by Doxygen for LAPACK from the source code.

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💖 That’s the whole page, bestie. Footer sign-off: LAPACK Version 3.12.0, source SRC/clacn2.f(3). The footer doesn’t list a date, so I’m not inventing one — just sending version + source with love. Bye! 💅✨