SRC/dlanst.f(3)

✨ NAME ✨

Hiii bestie 💖 welcome to the SRC/dlanst.f page from the Library Functions Manual. This is the whole glow-up for SRC/dlanst.f, and we’re keeping every detail, no cap.

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🌸 SYNOPSIS 🌸

🌈 Functions/Subroutines 🌈

double precision function dlanst (norm, n, d, e)

DLANST 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.

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🦋 Function/Subroutine Documentation 🦋

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

DLANST 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.

🎀 Purpose 🎀

Okay so the source is literally saying: 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. Iconic behavior, honestly ✨

⭐ Returns ⭐

Here’s the exact return formula, bestie — do not lose a single character:

!>    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.
!>

And yes, that last note is important: max(abs(A(i,j))) is not a consistent matrix norm. Periodt.

💖 Parameters 💖

🌟 NORM

NORM is CHARACTER*1. It specifies the value to be returned in DLANST as described above.

🌟 N

N is INTEGER. It’s the order of the matrix A. N >= 0. When N = 0, DLANST is set to zero.

🌟 D

D is a DOUBLE PRECISION array, dimension (N). These are the diagonal elements of A.

🌟 E

E is a DOUBLE PRECISION array, dimension (N-1). These are the (n-1) sub-diagonal or super-diagonal elements of A.

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👑 Author 👑

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

Definition at line 99 of file dlanst.f.

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🫶 Author 🫶

Generated automatically by Doxygen for LAPACK from the source code.

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💫 That’s the whole page, bestie — source/version footer stamp: LAPACK Version 3.12.0 SRC/dlanst.f(3). Slay. 💅