DLANST(3)

DLANST(3) 💅✨

okay so bestie, you opened the manual page for DLANST(3), and I am obsessed — this page comes from the Library Functions Manual, and it's all about the LAPACK routine that gives you norm vibes for a real symmetric tridiagonal matrix. no cap, it's giving “which norm is this” energy, and we are going to read it together. 🫶

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🌸 NAME 🌸

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

✨ SYNOPSIS ✨

Functions/Subroutines

• double precision function DLANST (norm, n, d, e) — returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a real symmetric tridiagonal matrix. 💖

🫶 Function/Subroutine Documentation 🫶

double precision function DLANST (character norm, integer n, double precision, dimension( * ) d, double precision, dimension( * ) e)

okay so this is the full signature, and yes it is a double precision function named DLANST. It returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a real symmetric tridiagonal matrix. Same energy as the synopsis, just with the whole signature spelled out. 🌈

🎯 Purpose

DLANST returns the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a real symmetric tridiagonal matrix A. That's the whole assignment, and it ate. 💅

🌀 Returns

DLANST — here's the exact mapping, bestie, don't let the parentheses scare you:

DLANST = ( max(abs(A(i,j))), NORM = 'M' or 'm'
         (
         ( norm1(A),         NORM = '1', 'O' or 'o'
         (
         ( normI(A),         NORM = 'I' or 'i'
         (
         ( normF(A),         NORM = 'F', 'f', 'E' or 'e'

where norm1 denotes the one norm of a matrix (maximum column sum), normI denotes the infinity norm of a matrix (maximum row sum) and normF denotes the Frobenius norm of a matrix (square root of sum of squares). Note that max(abs(A(i,j))) is not a consistent matrix norm. 🚨

🧸 Parameters

• NORM — NORM is CHARACTER*1. Specifies the value to be returned in DLANST as described above. ✨
• N — N is INTEGER. The order of the matrix A. N >= 0. When N = 0, DLANST is set to zero. 🫶
• D — D is DOUBLE PRECISION array, dimension (N). The diagonal elements of A. 💖
• E — E is DOUBLE PRECISION array, dimension (N-1). The (n-1) sub-diagonal or super-diagonal elements of A. 🦋

👑 Author

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

Definition at line 99 of file dlanst.f.

🎀 Author 🎀

Generated automatically by Doxygen for LAPACK from the source code. 💻

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xoxo, bestie — this page is from LAPACK, Version 3.12.0, and the footer path is /home/abui...RC/dlanst.f(3). slay. 💅💖